can I get it polished

grumpyvette

Administrator
Staff member
"HEY grumpy I got a good deal on a new forged 454 crank, but the guy I bought it from purchased it for a project and had it sitting on a shelf for over 5 years and its got a few rusty finger prints on the journals, can it be used?"


Since its a FORGED crank, Id bring it to a good machine shop, for a close inspection,and measurement ,and get their opinion,a good machine shop that can check it out, and polish it if required.
you could buy a cast crank for less than $300, a forged crank can easily cost more than double that money, so the $100-$170 most machine shops might charge to recondition the forged crank could easily be worth it, depending on the initial cost of the crank.
but in the majority of cases it can be polished or cut slightly under size, then it can be polished and will be fine,
get the machine shop to order the matching size clevitte (H) bearing set, and IF it was my project ID get the matching SCAT connecting rods pistons and rings, bearings, damper ,flexplate or flywheel, etc. and have the whole assembly balanced

proper magnets trap metallic debris
SmCo Samarium Cobalt Disc Magnets
http://www.magnet4less.com/
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if you don,t think a proper magnet can trap/hold and prevent metalic debriss from getting into the oil pump and bearings , look at this picture of an oil pan magnet I found posted
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Model# SMCO-D8

Samarium Cobalt Magnets 3/4 in x 1/4 in Disc
Suitable for high temperature applications
High Temp Samarium SmCo Cobalt Magnet Discs
572°F Maximum Operating Temperatu
re
Wholesale Price Range:
$2.99


adding a couple high heat tolerance magnets to the engine helps trap, the metallic debris,the finer stuff gets easily washed into the sump with the oil flow, any parts failure like that generates BEFORE the abrasive grit gets sucked thru the oil pump and be aware the oil filter won,t always prevent 100% of the grit reaching the bearings.
IVE typically used several of these magnets in any engine,Ive built, one in the rear oil drain on each cylinder head, one near each lifter gallery drain and 4 in the oil pan sump

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http://www.kjmagnetics.com/proddetail.asp?prod=D82SH
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BE AWARE magnets heat tolerance differs so ask for and pay attention to the heat limitations, a MINIMUM of 300F for any magnet expected to be used bathed in hot engine oil would be smart
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when you get the crank polished take the time and effort to clean out any cross drill oil feed passages and to very carefully de-burr the passage opening edges, as this is a very commonly overlooked issue, below is what at first looks like a perfectly polished crank, with oil feed passages to the rod bearings,
but the deep scratches the oil feed passage openings left in the rod bearing surfaces bare witness, after a single rotation, during a trial assembly show they are HARDLY burr free or ready for use, and obviously he failed to check each rod bearing during the assembly process, and probably ignored , what was very likely un-even or rather excessive resistance to the crank rotation. which should never exceed about 40 ft lbs even with all 8 rod bearings and pistons installed

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http://www.engineprofessional.com/TB/EPQ410_10-18.pdf
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Husam said:
This my first engine build and the crank (scat cast crank)got scratched as I was blueprinting it
Can I assemble with this scratch that I can barely feel it with my finger nail.

very clear detailed pictures , taken in good light from several angles would be very helpful, but I suspect from the very limited info that some polishing time with a long strip of some 800 grit wet/dry sand paper followed by 1200 grit paper used under a section of leather belt for support , will remove the burrs , BTW always polish the journal surface away from the direction or rotation,and use some WD40 on the paper,and it won,t take more than 20 passes (10 with each grit) to do it if its damaged lightly enough that you don,t need a machine shop to clear it up, that might get you back operational,but be darn sure to clean carefully to remove micro grit, that might be left on the surface, but you must know a few things to do it correctly
Crankshaft Grinding and Polishing


federal mogal said:
When refinished, the surface of a crankshaft will develop microscopic peaks which are “tipped” in the direction that the sparks spray during grinding (see the illustration above). If these peaks point toward the oil film area when the engine is running, lubrication is interrupted, and the bearing will show premature wear. It is important that the crankshaft be ground and final polished so that these peaks are tipped opposite the direction that the crank rotates when it is installed in the engine, this is referred to as the “favorable” direction. We recommend grinding the crank in the “favorable” direction, followed by a multi-step polishing process using progressively finer paper. The first polishing operation uses 280 grit paper with the shaft rotating in the reverse direction – this helps to “knock off” some of the raised material left over from grinding. The second polishing process uses 320 grit paper, and the crank should be rotating in the “favorable” direction. A third step polish with a very fine (400 grit) paper is optional, but should again be done in the “favorable” direction. If the thrust surface was contacted during the resizing operation it must also be polished.

HERES WHAT A MACHINE SHOP CRANK POLISHING BELT LOOKS LIKE

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care must be taken to ensure the journal does not get polished unevenly, tapered or egg shaped
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journal surface must be polished so micro burrs face away from the direction of rotation on bearing surface for max durability on bearing surface, burrs far to small too see or feel still induce wear
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Directions for crankshaft grinding and polishing
Crankshaft journal surfaces should be ground and polished to a surface finish of 15 micro inches roughness average Ra or better. Journals on highly loaded crankshafts such as diesel engines or high performance racing engines require a finish of 10 micro inches Ra or better.

The above is a simple straight forward specification which can be measured with special equipment. However, there is more to generating a ground and polished surface than just meeting the roughness specification. To prevent rapid, premature wear of the crankshaft bearings and to aid in the formation of an oil film, journal surfaces must be ground opposite to engine rotation and polished in the direction of rotation. This recommendation and examination of the following illustrations will help make the recommendation more clear.

Metal removal tends to raise burrs. This is true of nearly all metal removal processes. Different processes create different types of burrs. Grinding and polishing produces burrs that are so small that we can't see or feel them but they are there and can damage bearings if the shaft surface is not generated in the proper way. Rather than "burrs", let's call what results from grinding and polishing "microscopic fuzz." This better describes what is left by these processes. This microscopic fuzz has a grain or lay to it like the hair on a dog's back. Figure 1 is an illustration depicting the lay of this fuzz on a journal. (Note: All figures are viewed from nose end of crankshaft.)

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The direction in which a grinding wheel or polishing belt passes over the journal surface will determine the lay of the micro fuzz.

In order to remove this fuzz from the surface, each successive operation should pass over the journal in the opposite direction so that the fuzz will be bent over backward and removed. Polishing in the same direction as grinding would not effectively remove this fuzz because it would merely lay down and then spring up again. Polishing must, therefore, be done opposite to grinding in order to improve the surface.

In order to arrive at how a shaft should be ground and polished, we must first determine the desired end result and then work backwards to establish how to achieve it. Figure 2 depicts a shaft turning in a bearing viewed from the front of a normal clockwise rotating engine. The desired condition is a journal with any fuzz left by the polishing operation oriented so it will lay down as the shaft passes over the bearing (Figure 2).

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The analogy to the shaft passing over the bearing is like petting a dog from head to tail. A shaft polished in the opposite direction produces abrasion to the bearing which would be like petting a dog from tail to head. To generate a surface lay like that shown in Figure 2, the polishing belt must pass over the shaft surface as shown in Figure 3.

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The direction of shaft rotation during polishing is not critical if a motorized belt type polisher is used because the belt runs much faster than the shaft. If a nutcracker-type polisher is used, then proper shaft rotation must be observed (Figure 4). Stock removal during polishing must not exceed .0002" on the diameter.

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Having determined the desired surface lay from polishing, we must next establish the proper direction for grinding to produce a surface lay opposite to that resulting from polishing. Figure 5 shows the grinding wheel and shaft directions of rotation and surface lay for grinding when viewed from the front or nose end of the crankshaft. This orientation will be achieved by chucking the flywheel flange at the left side of the grinder (in the headstock). Achieving the best possible surface finish during grinding will reduce the stock removal necessary during polishing.

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The surface lay generated by grinding would cause abrasion to the bearing surfaces if left unpolished. By polishing in the direction shown in either Figure 3 or 4, the surface lay is reversed by the polishing operation removing fuzz created by grinding and leaving a surface lay which will not abrade the bearing surface.

Nodular cast iron shafts are particularly difficult to grind and polish because of the structure of the iron. Nodular iron gets its name from the nodular form of the graphite in this material. Grinding opens graphite nodules located at the surface of the journal leaving ragged edges which will damage a bearing. Polishing in the proper direction will remove the ragged edges from these open nodules.

All of the above is based on normal clockwise engine rotation when viewed from the front of the engine. For crankshafts which rotate counterclockwise, such as some marine engines, the crankshaft should be chucked at its opposite end during grinding and polishing. This is the same as viewing the crank from the flanged end rather than the nose end in the accompanying figures.

Unlike many engine bearings available today, Clevite engine bearings utilize a superior Clevite TriMetal™ material design. Stamped "Clevite®," this design incorporates the strength of a copper-lead alloy layer on a steel back and finally, a precision electroplated white metal "babbitt" third layer. TriMetal™ is an ideal bearing design producing good to excellent characteristics when judged for conformability, embedability, slipperiness and fatigue resistance.

We constantly monitor the function and operation of our full line of bearings, staying in touch with any changes or developments that new engines may require. And that translates into bearings that are better for your engine. If you're looking for the engine bearings that set the standards, specify Clevite®. Because you won't settle for second best.



The Moly platelets that make up the protective layers on your engine surfaces slide across one another very easily. Instead of metal rubbing against metal, you have Moly platelets moving across one another protecting and lubricating the metal engine parts.
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MOLY adds a great deal of lubrication to sliding metal surfaces , as it embeds in the micro fissures in the metallic surface's

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This coating effectively fills in the microscopic pores that cover the surface of all engine parts, making them smoother. This feature is important in providing an effective seal on the combustion chamber. By filling in the craters and pores Moly improves this seal allowing for more efficient combustion and engine performance.
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This overlapping coating of Moly also gives protection against loading (perpendicular) forces. These forces occur on the bearings, and lifters. The high pressures that occur between these moving parts tend to squeeze normal lubricants out.
related info
SPRAYING ALL VALVE TRAIN and BEARING SURFACE COMPONENTS DURING ASSEMBLY WITH MOLY REDUCES FRICTION
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pre-spraying all bearing and valve train components with a moly based spray, helps embed micro moly lubricants in the metallic surface micro fissures , a good paste lube like cranes assembly lube over the spray surface helps insure a good lubricant surface coating, that is far stronger than just the ZINC and PHOSPHATES in oil
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yes you generally need to verify clearances and journal taper and measure bearing journal roundness but in many cases a bearing thats slightly tighter can match the journals required clearances without going to a .010-.020,.030 under size.
Id also point out that occasionally guys forget to clean out the cross drilled oil passages resulting in metallic debris embedded in the bearings so clean carefully after any crank journal polish work
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HERES A PICTURE, main caps are usually cast with a arrow showing the direction they face but seldom number stamped to indicate the correct location in the block and its best to do that during the dis-assembly too insure they go back in the correct location.
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http://www.harborfreight.com/36-piece-14-in-steel-letternumber-stamping-set-60671.html

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its usually standard practice to lightly stamp the outward facing rods and rod caps and main journal caps with the cylinder number or location they will be or are located in and a matched stamped number on the oil pan rail of the block, its also useful to stamp the main caps on one edge and a matched stamped number on the oil pan rail of the block, indicating which direction each main cap faces and its location during the original DIS-assembly process or first engine assembly to prevent potential screw-ups during later builds or refresh builds.
just make the stamped number clearly readable but not deeply stamped as you don,t want to induce potential stress risers that might weaken the connecting rods

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https://goodson.com/blogs/goodson-gazette/inspecting-measuring-the-pistons-pins-connecting-rods

http://garage.grumpysperformance.com/index.php?threads/measuring-crank-bearing-journals.5478/

https://www.motor.com/magazine-summary/performance-perspectives-connecting-rod-inspection/

https://www.dragzine.com/news/tips-for-sizing-your-connecting-rods-correctly-from-callies/

https://mechanics.stackexchange.com/questions/51488/measuring-crank-and-rod-journals


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https://www.msdiscounttool.com/catalog/product_info.php?csv=gg&products_id=104046
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https://www.summitracing.com/parts/...MIwbuI4oP14AIVnrbACh1mLQA2EAQYBSABEgKanfD_BwE


https://www.tracxtar.com/2018/07/23/engine-assembly-the-bottom-end/

  • ENGINE ASSEMBLY: THE BOTTOM END
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AUTOMOTIVE
ENGINE ASSEMBLY: THE BOTTOM END
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By user666 / July 23, 2018
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We’ll get into the actual meat and potatoes of engine assembly: measuring main bearing clearances, measuring rod bearing clearances and checking crankshaft thrust dimensions. In the process, the crankshaft will be installed, the main bearing caps will be torqued and the bottom end will be readied for reciprocating component (rod, wrist pin and piston) installation.

Sounds complex, but the truth is there’s nothing fancy here except persnickety measurements, attention to cleanliness and plenty of patience. Bottom line: If you can muster up the persistence for detail, you can handle the job. It’s that simple. Here’s how it’s done.

Measuring the mains
The first step is to measure the crankshaft main bearing journal diameters. This is best accomplished on your workbench. We use a micrometer to check the dimensions in an “around the clock” pattern on each journal. What that means is that we check each of the main journals in multiple locations.

To properly use a micrometer, slowly tighten the spin wheel until the mic contact points meet the crank journal. Spin the bottom thumbwheel (ratchet stop) until you feel three clicks on the micrometer as it contacts the journal (keeping in mind you don’t want to scratch the journal surface either). Double-check to ensure that the mic contact points are touching the journal evenly (not cocked to one side). Lock the micrometer and check the reading. Record each reading as you go around the journal. In essence, you’re accomplishing two things: You’re checking for crankshaft main journal out of round (if the readings from different points differ) and you’re also checking the outside diameter of the crankshaft journal.

Follow the same steps around each main bearing journal and record each set of figures for each journal. On a typical modern V8, you’ll have five bearing journals to measure on the crankshaft.

There are two different times you can measure rod journal dimensions: right after you’ve finished checking the mains or later, once the crank is installed in the engine. If you’re confident the crank was properly machined, you can save those steps for later (which is what we’re doing here). If you’re not so confident regarding the crank accuracy, it’s best to measure it now. That way, if the dimensions are off you don’t have to go any further on the engine assembly job.

Finally, when using a micrometer, keep in mind that heat has an effect on readings. Never carry a mic around in your pocket and don’t hold it for excessive amounts of time. Additionally, when storing the micrometer, be sure the measuring contact points are left open so that temperature variations do not stress the instrument.

Next up, each main bearing has to be installed, and the assembled diameter has to be checked. The bearings should be cleaned and dry. We start at the front and work our way backward, beginning with main bearing number one (bearing caps are usually numbered and marked with an arrow facing forward). The idea here is to install the bearing, torque the bearing cap and measure the inside diameter of the bearing bore with the bearing installed. More detail below.

Install the main bearings
To install the main bearing, you’ll note there are tangs on the bearing insert (in the old days, they were sometimes called bearing “shells”). Most engines also have an oil hole in the block that coincides with the upper bearing insert. This oil hole links the main bearing to the main bearing supply machined within the cylinder block. Only one-half of the bearing set (inserts) per main journal cap will be equipped with an oil hole. It’s essential you get them right (hole in the bearing coinciding with the hole in the cylinder block-machined bearing web).

Begin the installation with the tang side of the bearing insert. Install in the block and then push the opposite edge into the main bearing bore. Repeat the process in the accompanying main bearing cap. Be sure the bearing is fully seated. You’ll note there is a small amount of bearing insert extending past the main cap as well as past the cylinder block bearing bore. This is the bearing “crush.” When the main bearing cap bolts are torqued in place, the bearing “crushes” into the outside of the bore. This ensures the bearing does not spin or turn during engine operation. At this time, you only need to install bearings on the number one main.

In most engines, the main bearing caps are numbered (the exception is usually the thrust bearing cap since it’s far different than any of the other bearing caps). Additionally, many main caps have an arrow that points forward: It goes toward the front of the engine. This arrangement places all of the bearing tangs on one side.

Oil the threads for the main cap bolts. We generally use good old-fashioned SAE 30 conventional (non-synthetic) for this purpose. Install the front cap (with bearing inserts in place). Thread the bolts in by hand and then using a soft face hammer (dead blow plastic or brass), seat the cap against the block. Torque the cap bolts to the factory-recommended specification. Generally, we use three equal steps (for example, 25, 50 and 75 foot-pounds), alternating between the bolts in each of the steps. On four bolt main caps, we start on the inner caps first then work outward. This tends to tighten the bearing cap evenly.

Check the clearances
Using an inside micrometer or dial bore gauge, measure the bearing inside diameter. Much like the crankshaft, we tend to measure the bearings (within the bore) in several different locations. Subtract the crankshaft outside diameter (measured previously) for journal number one from the bearing bore diameter. That resulting figure is the bearing clearance. Check the figure against manufacturer specifications. If the bearings are out of spec, you’ll have to juggle bearing halves (you can buy slightly under- and oversize bearings for popular engines) to come up with the appropriate clearance figures.

Repeat the entire process for all of the main bearings and caps. Once complete, remove all of the caps. Keep each cap and bearing intact. Leave the lower bearings in the cylinder block.

Installing the crankshaft
Depending upon the engine you have, it can be equipped with either a one-piece or two-piece rear main seal. No matter what format, it must be installed next. In either case, install the seal so that the lip faces inward (toward the engine). Clean the seal groove with a shot of brake cleaner and a fresh shop towel. The groove must be clean and oil free for the sealant to work properly. Apply a small amount of RTV silicone sealer on the seal groove in both the cylinder block and the main cap. Wipe up any excess (a wet finger works perfectly). Install the bottom half of the seal, or in the case of a one-piece seal, gently tap into place over the crankshaft (you can use a seal driver, but most seals easily tap on).

Apply motor oil (the same SAE 30 oil works) to the main bearings. Alternatively, you can use engine assembly lube (shown in the photo). It sticks with more tenacity than oil, providing more protection during the initial startup. Apply a small amount of engine oil or assembly lube to the main seal lip. Lower the crankshaft into place.

Reinstall the number one cap and the thrust bearing cap only. Seat the caps (using a soft face hammer). Install the bolts by hand, but don’t tighten.

Checking thrust clearance
Using a soft face hammer (plastic dead blow or brass), tap the crank nose (moving the crankshaft rearward). Install a dial indicator to read on the crank flange or nose of the engine. Using a large (clean) screwdriver or pry bar, move the crankshaft backward. Zero the gauge on the dial indicator. Pry the crankshaft forward and check the reading. Record the measurement. Next, torque the caps to specs and repeat the process. Compare the measurements. If the second reading is less than the first, there’s a chance the rear main cap shifted and the thrust surfaces are misaligned. Shift the cap and recheck. By the way, this doesn’t regularly occur, but if it does, you might have to check and shift the rear main cap a couple of times to get it right. Compare your final thrust clearance figure to the manufacturer specifications. Finally, install the balance of the caps (and bearings) and torque to specifications.

Checking the rod clearances
Beginning at the front of the engine, use your micrometer to check the overall diameter of each of the connecting rod journals on the crankshaft. The process is exactly the same as we used to check the main bearing clearances. Check each journal in multiple locations and record those figures.

You can now check the rod bearing clearances. Use the same process we used for the main bearing caps: Install the bearings with the tabs aligned. You can match the numbers on the rods or check to ensure the chamfers are all on the same side and install the caps. The bearings (and caps) are aligned tang to tang (not offset). Using engine oil as the lubricant, torque the cap bolts to the recommended figure and measure the bearing ID with a bore gauge.

Subtract the journal diameter from each of those figures to determine the clearance. Repeat the process for all of the connecting rods. Like the case with the main bearings, if the clearances are out of spec, you can often correct the dimensions by juggling bearing inserts.

Once all of the rod clearances have been checked, you can loosen the rod bearing cap hardware, but don’t completely disassemble. You need to keep the rods and their respective bearings in order. Wrap the engine in the plastic storage bag. You’re done with this segment.

In the next part of our series, we’ll show you how to file-fit piston rings to each cylinder, how to assemble rods onto pistons, and, ultimately, how to install all of the pistons and rods in the engine short block.

Tools used for this part of the assembly:

  • Dial bore gauge
  • Dial indicator and magnetic base
  • Two-third-inch micrometer
  • Half-inch drive torque wrench
  • Three-quarter-inch and half-inch drive sockets
  • Seven-sixteenths-inch 12-point half-inch driver socket
  • Large pry bar
  • Deadblow hammer
Using “Plastigage”
If you don’t have access to a dial bore gauge (or inside micrometer set) or an appropriate outside micrometer, you can still check bearing clearances with “Plastigage.” Plastigage is a special extruded plastic thread (think of an advanced version of kid’s plastic modeling clay or Silly Putty). The difference though is the stuff is engineered so that it includes controlled crush properties. It’s available at most auto parts stores, in various different crush dimensions to coincide with the clearance figures for your engine.

To use it, loosen the bolts of bearing cap number one. Remove the bolts along with the cap (and bearing). Wipe all traces of oil from the crankshaft and bearing surfaces (we use a paper towel).

Next, tear off a short piece of Plastigage (it’s sold in a long, thin paper envelope). Place a section of Plastigage on the center of the crankshaft journal, oriented front to back or diagonally.

Install the bearing cap and bolts. Torque to specifications, then loosen the bolts once more and remove the cap. You’ll find the Plastigage has crushed on the crankshaft journal.

Using the envelope the Plastigage was packaged in, you’ll find a scale on one end. Compare the scale to the crushed Plastigage on the bearing journal. This is the clearance figure. If the clearances are within specifications, you can move forward: Clean the journal (it wipes off with a towel soaked in brake cleaner) and repeat the process for all bearing journals. You can also use the same format for checking connecting rod bearing clearances.

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The first step in determining bearing clearances is to measure the crankshaft main journal diameter. Here we’re using an outside micrometer to get the measurement. The article text offers details on how it’s done and tips on using a mic. Check all crankshaft main bearings and record your figures.

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Next, install the main bearing insert for journal number one in the cylinder block. Note the orientation. The oil hole in the bearing half aligns with the oil hole in the main bearing.



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The matching bearing insert for the main cap is installed next. Because of the need for bearing crush, the insert will seem marginally too big, and a minute portion of the insert will protrude past the edge of the cap (the same applies to the insert in the block).

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Install the cap and torque the main bearing cap to specs. Typically, we begin with the inside bolts and work outward. In addition, it’s best to use three steps on each of the fasteners in order to “sneak up” on the final torque figure.

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With the bearing installed in the cap and the fasteners torqued to specifications, you can measure the main bearing inside diameter. Here, we’re using a B&B Performance dial bore gauge for the measurement. Subtracting the crankshaft journal figure from this measurement provides the bearing clearance. Record all measurements and repeat this process for all bearings except the rear main.

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Before measuring the rear main bearing inside diameter, install the oil pump and torque to specifications. The reason is there is always the chance for some distortion of the cap once a heavy oil pump is installed. Here, a huge Titan G-Rotor oil pump is installed and torqued to specs.

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Once you’ve checked all of the main clearances (and they’re all within specification), you can install the crankshaft. You can use conventional engine oil for the installation or assembly lube. Apply a light coating to the lower main bearing halves.

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Next, the rear main seal is installed. With a one-piece seal such as this, it must be slipped over the rear of the crank prior to lowering the crankshaft into the block. The article text offers more detailed info, but in this photo you can see the installed seal.

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With all of the lower bearing inserts in place, you can gently lower the crank into the main bearing saddles. You can reinstall the rear main bearing and cap along with the first (front) bearing cap.

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Checking the crankshaft thrust dimension is next. You’ll need a dial indicator setup to read front-to-rear movement on the crankshaft. Depending on how you choose to perform the job, the dial indicator can be set up on the nose of the crank or on the rear flange. For this job, we have access to the flange on the engine stand (it needs to be tapped with a hammer), so we set the dial indicator up on the nose. The text offers details on how this job is accomplished.

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All of the main bearing cap bolts (or studs) can be torqued in place. We use a half-inch drive torque wrench for the job, and while we have three other torque wrenches in our tool collection, this long handle one makes torquing large numbers easy. What’s with the blue line on the outer row of bolts? It’s used to note which caps have been fully torqued. That way you can’t forget if you’re called away. We always double-check them.

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Measuring the rod bearing clearances is next. Here, the number one and two rod journals on the crankshaft are measured using a micrometer. Much like the main journal measurements, it’s a good idea to check in multiple places around the journal. This determines if the journal is in fact round. Repeat the process on all of the bearing journals and record the measurements.

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At this point, the connecting rod bearings can be installed. Note the chamfer on the bearing is designed to match the chamfer on the connecting rod. You’ll also note the bearing tangs are next to one another. If the connecting rod (and cap) is unmarked, this orientation ensures the cap is installed correctly. When assembling the engine, the chamfer faces the large fillet radius on the crankshaft.

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With the bearing installed and the cap correctly oriented, you can torque the connecting rod fasteners to specification. In this case, the GM Performance Parts connecting rods mandated 30W oil as the lubricant during tightening. Sneak up on the final figure just as you did with the main bearing caps.

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Here, we’re using our B&B Performance dial bore gauge to determine the inside diameter of the rod bearing (installed within the connecting rod). Once this figure is determined for each connecting rod, subtract the crankshaft rod journal dimension to determine the oil clearance. FYI, the best way to measure bores such as this is by way of a dial bore gauge.
 
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refurbishing connecting rods clearances, takes precision measuring tools and a good grasp on whats required.
Connecting Rod Reconditioning: More to it than you might think
Brendan Baker,AUTHOR

The connecting rod plays a vital role in the engine. But a connecting rod is under tremendous stress, with the weight of the piston sitting on top, changing direction thousands of times per minute. This continuous stopping and changing of direction combined with the weight of the piston and speed of the engine hammer on the bearings and torture the rod bolts which hold everything together.

Proper geometrical alignment and bearing surfaces that are smooth and perfectly round is the best way to ensure long engine life and happy customers. Any unwanted lobing, chatter or misalignment, particularly in engines that operate at high rpms, will affect the engine’s efficiency.

One of the most important aspects of rebuilding an engine is to recondition the connecting rods. There are many different types of connecting rods from cast steel to powdered metal “cracked” rods to all the various types of performance rods. The processes used to recondition this engine component may vary a little from one rebuilder to the next, but the end goal is always the same – straight rods with round bores. Sounds simple, but like anything worth doing, there’s always more to it than you think.

Typically, reconditioning rods involves cleaning them thoroughly, then checking them with magnetic particle inspection for any cracks. Then the rods are checked for straightness because any bend or twist in the rod may result in oil clearance problems and likely lead to a failure.

A visual inspection of the rods will also include looking for any signs of overheating, which may be indicated by a “bluish” appearance. If the rod has been overheated, its structural integrity may have been compromised, according to the rebuilders we interviewed for this article

“If a guy has overrevved his engine, we go through and magnaflux all the parts,” says Kenny Burns, Harry’s Machine Works, Dodge City, KS. “Connecting rod material is typically pretty good, but sometimes the machine quality leaves something to be desired. Therefore, we check everything, even brand new rods.”

On the performance side, some rebuilders will check the hardness before declaring them fit for the junk pile. “You can test the heat treatment with a Rockwell tester,” says Roger Friedman, Dyer’s Top Rods. “We know what our rods should be. They’re usually in the 42-43 range on the Rockwell C scale. If a rod got hot enough to change that, it’s junk to us.”

Friedman cautions that color isn’t always a true indicator, however. “We’ll sometimes see some rods that were affected when an oil pump belt came off, for example. If you catch them soon enough, they will still turn color, but if the rods test okay, we will shot peen them, re-cut and resize them and reuse them.”

After the rod has been cleaned and inspected thoroughly, it should be put back together with the rod bolts torqued. With a stretch gauge, check each rod bolt for proper stretch. If the stretch is out of spec, then replace the bolt. While some engine builders say that it is safer and less expensive to just replace the rod bolts instead of measuring the stretch, others say that practice really depends on the application, because some high performance rod bolts can be quite expensive.

After the caps are torqued on with acceptable rod bolts, measure the big end bores. This will help you to determine how much to take off the caps and to what size you’ll need to hone them. In general, you want to take off as little material as possible to make the bore round again. After you hone the big end, measure the rod to see what size bushing you need to put in the pin end.

“The ultimate goal when reconditioning rods, is to come up with a set of rods that are straight and of the correct length,” says Jay “Dr. Diesel” Foley, of Foley Engines, Worcester, MA. “In common four- and six-cylinder gasoline and diesel engines, the rods must be machined back to original specs with no more than .0025″ of bend and no more than .00425″ of twist. A rod with too much bend will limit oil clearance from one side to the other and possibly lock up the engine at the pin end or at the thrust on the crankshaft. In addition, they must have round and concentric bores, and the fasteners must also be able to withstand the stresses of a modern engine.”



Once the connecting rods are bored and honed, then you can put the proper size bushing in the small end, which itself is a very important step. “We are very concerned about the piston-pin bushing relationship,” says Foley. “We always press out the old piston-pin bushing and install new ones. But that is only half the battle. To ensure that the bushing won’t rotate, we expand it to conform to the small end bore. To expand this bushing we press a hardened steel ball through the ID of the new bushing. This will lock in the new bushing and prevent it from spinning in the bore. If you heat the rod to install the new bushing, you should allow it to cool before you expand the bushing with this broaching technique. Then grind the cap to the correct center-to-center dimension and hone the big end and install new rod bolts.”



According to Harry’s Machine Works’ Burns, keeping the rod straight is very important. However, one of the difficulties his shop faces is finding aftermarket wrist pins that are the correct size. “Some aftermarket suppliers are making wrist pins that are supposed to be the same size as OE but they are not,” he explains. “We have had a hard time trying to get the right sizes. Sometimes the pins are .001? to .003? off the OE specs. Within that application we have seen differences of up to .003? and we’re trying to keep the tolerance within .0002″ to .0003″.”



Burns says that his shop uses a similar process to Foley’s for reconditioning connecting rods. Both Foley Engines and Harry’s Machine primarily rebuild diesel engines. Rebuilding diesel rods isn’t much different than gas engine rods, except they’re much bigger and the center-to-center distance is has to be exact. Since diesel engines operate on a compression cycle, rod lengths have to be correct. “We can shorten them or lengthen them,” Burns says about diesel rods, “it just depends on how much has been taken off the block. So the center-to-center distances are critical.”



Fractured Rods

Fractured rods are a fairly new phenomena. Ford was one of the first on the automotive side to use a fractured rod in the 4.0L engine, which was one of its first new generation engines in 1990. The fracture method has proven to be less expensive for manufacturers and it produces better quality because it is forged in one piece and then ‘cracked’ at the rod cap.



“Before fractured rods were invented, conventional rods were two components,” says Dave Hagen of the Engine Rebuilders Association (AERA). “You would have one piece, which was the cap and another that was the beam. The two pieces were close enough to bolt together; then you would have to do several machining operations to get the center-to-center distances correct. The fractured rod, on the other hand, is a powdered metal rod that allows the manufacturer to pop it out like an egg with very little machining to make the size exactly right. It comes out essentially the final size and then is broken at a scored line that is part of the design. Once it’s broken or ‘cracked,’ it’s done. It can be manufactured for far less cost than a traditional rod and it’s a more durable component.”



According to Hagen, the inside diameter of a fractured rod bore is scored and then some pressure is applied until it snaps. The resulting split is like a piece of china that has been broken. It has a very distinctive surface that custom fits together. The fracture has more surface area because you have peaks and valleys, and the alignment is more accurate since the cap only fits together one way.



For rebuilders, there’s not much you can do with fractured rods. You can’t cut the caps because of the unique break on each one. And for the most part, you cannot hone the bore because there are very few oversize OD bearings available for them. Hagen says that some suppliers carry oversize OD bearings for the big end of the more popular models, like the modular 4.0L and 4.6L Fords, but it’s uncertain if there are any bushings available for the pin end. So there’s a little bit of rebuildability with fractured rods but not much.



Now, some heavy-duty manufacturers are going to fractured rods. “There are some heavy-duty manufacturers making them, like John Deere is coming out with some now, but with fractured rods we can’t do much with them,” acknowledges Harry’s Machine Works’ Burns. “We measure them to check the size, and that’s about all we can do until there are oversize OD bearings available.”



New Methods

For years, connecting rods have been honed on specialized rod honing machines, which are available from many leading manufacturers. These machines have been the standard, produce excellent results and are still widely used throughout the industry. However, Sunnen and Rottler have both recently come out with new systems that take a totally different approach to rod reconditioning.



Sunnen’s system is called the KGM-1000 Krossgrinding System®. The KGM system utilizes an easy-to-use computer control, diamond tooling and a feed system that gives the operator high accuracy and speed in the production of precision reconditioned connecting rods. The company says the system is extremely accurate for honing connecting rods, and is capable of holding very tight tolerances, achieving accuracies of .00001″ in straightness and .00015″ in roundness.



Rottler has also designed a completely new system that works with the F-65 and F-67A multi-purpose machines. According to Rottler’s Anthony Usher, the company wanted a system that could bore both the big end and the small end in one setup.



“When we decided to get into the rod reconditioning business,” Usher says, “one of the big problems we saw was that rods bend and twist. When you have two setups you can sometimes create other problems. We decided to design a system where a rebuilder could lay the connecting rod horizontally and set it up so both the big end and the small end could be open. With both ends open you can machine both ends in one machine and in one set up and achieve perfect parallelism between the centerlines of both ends.”



Rex Crumpton Jr., of Memorial Machine in Oklahoma City, OK, says his shop has both a Berco rod honing machine and a new Rottler system. According to Crumpton, both systems work excellent and he can achieve good results either way. Memorial uses the Berco machine for doing smaller stuff and the Rottler for reconditioning larger rods.



“Honing is excellent, there’s nothing wrong with doing rods that way,” says Crumpton. “But boring can be a bit more precise. You don’t have to worry as much about stones loading up, which could produce taper. As long as you have a good operator who is paying attention, both methods work fine.”

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http://www.tooltopia.com/fowler-72-646-300.aspx

https://www.amazon.com/Anytime-Tools-MICROMETER-Machinist-Precision/dp/B000JMW4AS

 
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https://goodson.com/blogs/goodson-gazette/connecting-rod-honing-basics

https://www.motor.com/magazine-summary/performance-perspectives-connecting-rod-inspection/

https://www.hotrod.com/articles/hrdp-1212-dont-bother-building-factory-aftermarket-connecting-rods/

http://garage.grumpysperformance.com/index.php?threads/reusing-stock-connecting-rods.702/


http://www.engineprofessional.com/EPQ2-2014/files/inc/812367d726.pdf

Reconditioning connecting rods
  1. Experts say reconditioning connecting rods involves thoroughly cleaning them first to check for any visible damage. ...
  2. The main purpose of reconditioning rods is to build a set of rods that are straight and of the correct length. ...
  3. After the caps are torqued on with acceptable rod bolts, measure the big end bores.

https://www.enginebuildermag.com/2007/10/back-to-basics-reconditioning-connecting-rods/

Back to Basics: Reconditioning Connecting Rods

When you’re looking at connecting rods and considering returning them to service, there are many things you must consider. They are one of the most critical pieces of the engine puzzle and under great strain when in operation, so you must pay attention to the details during the rebuilding process.

There are many times when reconditioning the connecting rods is a necessary part of engine rebuilding. In many applications it is acceptable, and significantly less expensive, to rebuild rather than replace a set of rods. In the heavy-duty market, for instance, many engine rebuilders prefer to recondition the connecting rods whenever possible because the components are typically expensive to replace and it’s not always necessary. However, like the rest of the engine, there are "best" practices that must be followed to ensure a quality engine build and to avoid costly comebacks.


Experts say reconditioning connecting rods involves thoroughly cleaning them first to check for any visible damage. After cleaning and inspecting them, you may find obvious clues that damage exists. Knicks and burrs, or discolored rods can often be signs of a rod that will fail down the road.

The next step is to put the connecting rods through a magnetic particle inspection (MPI). This step will reveal any hidden damage such as cracks or other stressors and imperfections that cannot be seen. After the MPI has been performed, if the rods still look to be in good shape, they should be checked for bend and twist, which if too much, may negate the rest of the reconditioning process. Experts say too much bend or twist may have been the result of an over-revved engine or insufficient oil clearance, and if not properly straightened or replaced, will lead to certain engine failure.

Careful inspection and handling isn’t reserved only for used rods, however. One engine builder cautions that you should always check the connecting rods thoroughly even when they’re new, because you never know when one will be out of spec and create problems down the road. And new or used, that’s the last thing you want to have happen to your rebuilt or remanufactured engine.


The main purpose of reconditioning rods is to build a set of rods that are straight and of the correct length. In typical light-duty applications, four- and six-cylinder gasoline and diesel engines, experts say the rods should be machined back to original specs with no more than .0025" of bend and .00425" of twist. A rod with too much bend will limit oil clearance from one side to the other and possibly lock up at the pin end or at the thrust face on the crankshaft. Furthermore, they must have round and concentric bores, and the fasteners must also be able to withstand the stresses of that application – whether it’s a performance engine or heavy-duty application.

To ensure long engine life, the rods must be aligned correctly and the bearing surfaces must be smooth and perfectly round. Any lobing, chatter or misalignment, particularly in engines that operate at higher revs, will affect the engine’s performance.

After the rod has been cleaned and inspected thoroughly, it should be put back together with the rod bolts torqued. With a stretch gauge, check each rod bolt for proper stretch. If the stretch is out of specification, then replace the bolt. While some engine builders say that it is safer and less expensive to just replace the rod bolts instead of measuring the stretch, others say that practice really depends on the application, because some high performance rod bolts can be quite expensive.


After the caps are torqued on with acceptable rod bolts, measure the big end bores. This will help you to determine how much to take off the caps and what size you’ll need to hone them to. In general, you want to take off as little material as possible to make the bore round again. Experts say you should not take off more than .002" of material off the big-end at a time. After you hone the big end, measure the rod to see what size bushing you need to put in the pin end.

If during the inspection process a bent or twisted rod is found, it may be possible to straighten. One method of correcting bend or twist is called cold bending. This can be achieved using a special holding fixture. When performing this procedure, it is important not to nick or scratch the rod, caution experts. Nicks and scratches weaken the connecting rod and may lead to possible breakage.

Experts say you must first determine the direction of bend or twist. Most bends in the rod will be located near the small-end bore. Place the connecting rod into the straightening fixture using the correct size big-end and small-end adapters. Install the cap and torque the cap bolts to specifications. Select the appropriate bending bar. It should closely fit the rod to prevent nicks and scratches. Use the bar to bend the rod in small increments. Measure the progress on a rod alignment fixture.

Once the connecting rods are straightened, bored and honed, then you can put the proper size bushing in the small end, which is a very important step according to some engine builders. It is recommended that you press out the old piston-pin bushing and install new ones. And to ensure that the bushing won’t rotate, you should expand it to conform to the small end bore. To expand this bushing, press a hardened steel ball through the I.D. of the new bushing. This will lock in the new bushing and prevent it from spinning in the bore. If you heat the rod to install the new bushing, you should allow it to cool before you expand the bushing with this broaching technique. Then grind the cap to the correct center-to-center dimension and hone the big end and install new rod bolts.

There are many different types of connecting rods from cast steel to powder metal (PM) "cracked" rods to all the various types of performance rods.

More than half of the connecting rods used in today’s late model engines are powder metal I-beam design. PM rods are constructed by compressing powdered steel into a mold and heating it to a high enough temperature where the powder melts and fuses into a solid piece. This process allows the rods to be cast with very precise tolerances, thus reducing the amount machining required to finish the part, making it less expensive to produce higher quality rods.

PM rods are made up of a composite of alloys that allow rod caps to be "cracked" at the parting line rather than split with a straight cut. Many PM rods are not serviceable because you cannot grind down the caps to bring it back to original specifications. In some cases, there are oversize O.D. bearings available that will allow you to hone the big-end and fit a larger bearing.

The benefit to manufacturers is that the fractured PM rod is popped out like an egg with very little machining to make the center-to-center distances right. It comes out of the casting process the final size and is broken at a scored line that is part of the design. PM rods can be manufactured for less cost than traditional rods and is a more durable component, experts note.

The resulting fracture is like a piece of broken china. It has a very distinctive surface that custom fits together. The fracture has more surface area because you have peaks and valleys, and the alignment is more accurate since the cap only fits together one way.

For engine builders, there’s not much you can do with fractured PM rods. You can’t cut the caps because of the unique break on each one. And, for the most part, you cannot hone the bore because there are very few oversize O.D. bearings available. Some suppliers carry oversize O.D. bearings for the big end of popular applications, but we’re uncertain if bushings are available for the pin end.

For performance applications, some engine builders check the Rockwell hardness level of the rods before continuing with a rebuild. Performance rod manufacturers know what heat treatments have been applied and what hardness range is acceptable. Before reconditioning a performance rod it may be a good idea to contact the rod manufacturer. One manufacturer of performance rods says that any rod over 43 Rockwell C, isn’t worth rebuilding. If the hardness level has dropped, it’s a good indication that the rods were overheated and it has affected the heat treatment. Experts also caution that the color of the rods may be misleading, if the problem is caught soon enough and it hasn’t affected the heat treatment then they’ll probably be acceptable to recondition.

After rods pass the hardness test and are cleaned and inspected, the caps should be bolted back on and then torqued to specification. Using a stretch gauge, check each rod bolt for proper stretch according to manufacturer specifications. Some experts say you that you should replace all rod bolts as a matter of practice but others say it depends on the application because performance rod bolts can be expensive.

It is recommended that if the rod requires straightening to replace the rod bolts after the straightening process. Most connecting rod bolts are press-fit into the connecting rod, so it’s a good practice to press both bolts out at the same time instead of hammering them out one at a time. They should press out easily. If excessive pressure is required, you may have to heat them in a rod heater, otherwise you could break or bend the rod.

After the caps and rods are machined, new bolts can be installed. When installing the bolts, it is important to protect the parting surface of the rod. A fixture can be made or purchased for installing the bolts. With the rod located over the fixture, the bolts can be seated with a punch or hammer.

Reconditioning connecting rods is an important and often times a necessary step in the engine rebuilding process. They are under tremendous stress from continuously stopping and changing direction, combined with the weight of the piston and speed of the engine beating on the bearings and pulling on the rod bolts that hold everything together. The processes used to recondition connecting rods vary a little from engine to engine but the end result should be the same – straight rods and smooth, round bores.
 
https://www.enginebuildermag.com/2005/01/crank-and-cam-polishing-are-you-smooth-enough/

Crank And Cam Polishing: Are You Smooth Enough?
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Brendan Baker,AUTHOR



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Manufacturers are designing today’s engines with tighter tolerances and less room for error. They make more power, live longer, produce less noise, vibration and friction, burn less fuel and produce lower emissions. So in light of all this, it is more important than ever for engine builders to be as perfect, or near perfect, as possible when it comes to surface finish requirements.




Crankshaft and camshaft finishes are no exception. In today’s engines, rotating assemblies ride on a thin wedge of oil only .00005? thick in some cases. And to help reduce friction as much as possible, oil itself is much thinner today as well, so it is especially important to achieve the proper surface finish on all components in order to avoid problems down the road.



Engine builders big and small have the same need to produce a smooth surface on cranks and cams, but their respective budgets and business volumes may dictate what equipment is used to get the job done properly. Large production engine remanufacturers (PERs) can justify purchasing a micropolisher and an automated surface finish gauge while small custom engine rebuilders (CERs), by-and-large, feel they can’t afford such luxuries. This is not to say that it’s out of the realm of possibility for CERs to afford a micropolishing machine or a surface finish profilometer; but higher volume is generally what justifies making such a purchase.




Belt Polishing

Belt polishing is the traditional method, used by engine builders for many years, to polish crankshafts as well as camshafts. In the past, belt polishing worked well to easily produce surface finishes that were extremely close to OEM levels. Today, however, vehicle manufacturers have automated industrial polishing machines that cost many thousands of dollars and produce very smooth and consistent results, results that are increasingly more difficult for engine builders to reproduce with manual equipment. Difficult, perhaps, but not impossible.




"We achieve an extremely fine finish on the grind, before we polish." says Bob Heidbreder, Northampton Crankshaft in Cuyahoga Falls, OH. "Our method is to first dress the grinding wheel very fine and then use polishing belts for the final finish. We do all different styles of crankshafts this way and we’ve never had a failure or a comeback because of the finish."



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Customarily with late-model crankshafts, says Heidbreder, rebuilders mic the journals and go through a two-step polishing process. "If the crankshaft is salvageable and you don’t have to grind it, you polish it with a #400 grit aluminum oxide polishing belt. And then, if you need, you would have the option to micropolish the crank to achieve a finer Ra finish. Of course, this depends on the crankshaft you’re working on but most want it as smooth as possible."



Aftermarket distributors recognize the demand for near-OE quality finishes and offer rebuilders a number of products. "We have a brand new belt that we introduced about a year ago," says Chris Jensen, Goodson Shop Supplies, Winona, MN. "It’s a GSW micropolishing belt and it is the best thing we’ve found for final crank polishing. You put it on with a little crank polishing rouge and turn it approximately 10 rotations."



According to Jensen, these belts have even worked well enough for a number of NASCAR racing teams to give them a try. These teams now use them for final polishing the cranks in their race engines.



"What is so nice about this belt is that there’s a serration on it so it can polish the large radius on these high performance cranks," says Jensen. "High performance cranks have a large radius for strength while many production engines have virtually no radius."



A number of other distributors offer micropolishing belts as well as portable belt polishers. Tom DeBlasis, K-Line Industries, Holland, MI, says portability brings polishing capability to the price range and user abilities of almost every rebuilder.



"We offer a couple of portable crankshaft polishers: one electric and one pneumatic, which can be used on either a crank grinding machine after you move the head away or on a rotating polishing stand," says DeBlasis. "Most guys start out with a #320 grit belt, then go to a #400 grit and then progress to a very fine micro-polishing belt for a few revolutions, depending on the application."



Micropolishing

"A long time ago stones were used to polish cranks and cams but that technology has gone by the wayside now," says Ken Barton, QPAC, Lansing, MI. "Today, micropolishing is technically the most advanced way to achieve OEM-level surface finish on cranks and cams."



Barton says many engine builders believe in some polishing "myths," which can impact a shop’s profitability. "Some rebuilders believe if you use very fine grit belts you will not remove any material. That’s kind of a misconception. You always take off some metal when you polish," says Barton.



"When you are done grinding the piece with the grinder it looks like a mountain range," Barton continues. "If you put a micrometer on the piece you’re going to measure from the highest peak to the highest peak. So when we take those peaks down and you remeasure it, you’re going to get a different measurement. It might be just a small amount of material, but some material is being removed."



Typically that amount may be as small as .0002? according to Barton. One of the challenges is convincing shops that such a small amount actually makes a big difference. "Of course, you have to take material off to achieve the correct surface finish. With micropolishing you’re taking off the peaks and getting down towards the valleys, and the more peaks you remove the more surface area you have," he says.



Another misconception that some users have is they think they can put a polishing belt on and go crazy with it. "Some people think making the part shiny is enough, but it probably has taper, crown and who knows what else," says Barton. "If it is within a couple of tenths the error is still there. That’s why we back our machines up with a rigid shoe behind the tape. So now you have a rigid setup that won’t taper or go out of round. That way we keep things round and flat. When you finish you index the tape approximately one inch and go on to the next journal."



Micropolishing machines use a polishing tape instead of a belt like a belt polisher does. The tape comes in approximately 150-ft. rolls, and when used on a micropolishing machine operators index each roll after each use. When a crank or cam is polished on one of these machines, it uses about one inch of tape per journal, so fresh abrasive is used for every polishing job, but because it’s such a small amount, many users say they’ve saved money. "One PER reported a 50-75 percent savings in the cost of tape vs. belts," Barton says.



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The type of abrasive tape you should use for grinding cranks and cams varies, according to Barton. "From our position it all depends on what is on the machine. Is it a steel, cast iron or nodular iron part? Is it a hardened steel or is it a forged part? Then once you get through the material, what kind of surface are you grinding? We’ve had surfaces as high as 45 Ra and as low as 15 Ra. All that determines what abrasive you use on the polishing tape. It could be 9 micron or it could be 50 micron (note: 20 micron is roughly equal to #600 grit). It just depends on how aggressive you need to be."



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Barton understands that not every shop will purchase his equipment. "For shops to really see a payoff they need to rebuild about 15 cranks or engines a day. Some specialty and high performance shops that sell engines and cranks for much higher prices than average can also make their ROI."







Measuring the Finish

According to some of our experts there are still engine builders who refuse to use any measuring devices other than a fingernail to measure surface finish. Yet increasingly, it is more important than ever to know exactly what surface finish you have. Without a measuring system, however, you can’t know exactly what you have when you finish polishing.



While you don’t have to measure every piece, measuring Ra during a spot check is a good step toward safeguarding against problems you may not even know exist. There is hope that this trend is going to change as the industry becomes more aware of the need to measure surface finishes.



K-Line’s DeBlasis says that a lot of engine builders are at least starting to look at portable profilometers. "Profilometers are not inexpensive and I think that’s why some smaller shops are just looking right now, but we’re starting to sell more of them," says DeBlasis. A portable profilometer can cost up to $2,000, according to DeBlasis.



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There are three characteristics to understand about surface finish: profile, waviness and roughness. According to John Wilt who works with the American Society of Mechanical Engineers Board of Standards on surface finish specifications, a sand dune is a good example of all three. "The overall shape of the dune would be equivalent to the profile, and as you moved in closer to see the windswept ridges, that would be waviness, and the grains of sand would represent roughness," Wilt says. "Every crank and camshaft has these three features as well, and technically they all fall under the heading of ‘surface finish.’"



However, just because they all represent an element of surface finish, it’s important to approach each component separately.



"Profile is the size of something," says Wilt. "It could be the diameter. It could be the shape as far as being round or tapered or hourglass shaped. Profile can also be a length measurement. So the journals and the lobes all have to be the right shape and in the right location."



The second phase of surface finish is waviness or lobing. "If you go along the axis of a crankshaft journal or camshaft journal it would be considered waviness. If you go around the part it’s now called lobing. And a very frequent slang term used for this is called chatter. If waviness is out of spec, that’s where problems with noise and vibration come into play.



"Basically, if you go back to the sand dune analogy, if you were to walk a little closer to the dune and saw all the windswept ridges, there’s something separate that caused that to happen than the profile itself," says Wilt.



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The third phase of surface finish is roughness. "If you walk up and grab a handful of sand from the dune, you’ll recognize that the grains represent roughness. Surface finish is kind of like grains of sand paper that over time creates wear. The valleys in the grains of sand actually are a major contributor to holding lubricant," says Wilt.



Wilt’s company, Adcole, manufactures surface finish equipment designed to measure all three categories independently. It can measure a crankshaft or a camshaft, giving the manufacturer or rebuilder the ability to look at the shape, size and location first (profile) to ensure that it’s correct. "If the profile is not right the rest doesn’t matter. If it doesn’t assemble or go together it’s not going to work anyway," Wilt notes.



Roughness Average?

When you read the term "Ra" does it mean anything to you? "If you ask anybody in the industry, we’ve all seen a surface finish symbol: a checkmark with a number, or the roughness symbol," says Wilt. "The problem is that most people assume they know what it means."



While shops can often easily get an Ra reading using a handheld device, they may not really understand what it means. One reading may be different than another. According to Wilt most people think Ra is the peaks and the valleys – but it is only an area measurement.



Wilt continues. "If you say you have an Ra of one micro-inch it’s hard for people to understand just what that means. It’s like if I say I have one acre of land for sale for $5,000: would you want to buy it? What do you know about my acre of land? You know only one thing – it’s an acre and it’s got so many square feet. If you know the area is rectangular then you can describe it by its spacing and its peaks, but you really don’t know anything about the area. Saying a surface has such an Ra is exactly the same thing."



"When you have your Ra you don’t really know what that looks like," Wilt explains. "It could look like a saw tooth or it could look like a square wave, where it goes up and goes across a little and then it goes down or it could be much spikier or wavier. The net result is you have different capabilities for bearing load. In many cases, simply looking at the roughness average is not necessarily the best way to look at that surface. You want to make sure there’s enough bearing area and you also want to make sure you don’t gouge the bearing surface. So ultimately the part that’s contacting the connecting rod bearing, for example, must have enough surface to bear the load. It’s not just two contact points that will be crushed as soon as the engine rotates."



Favorable and Unfavorable Direction

One way to achieve the proper surface finish on cranks and cam journals is to grind them in the opposite direction they normally rotate in the engine. Most automotive cranks typically rotate clockwise, but some industrial and marine engines rotate counter clockwise. So you have to know which way the engine rotates before you mount it in the polishing stand.



Polishing the crank or cam in the opposite direction it was ground will also break off more of these ferrite burrs, leaving a cleaner smoother finish as well. Ferrite burrs, if not removed, can cause problems later on because they can wipe away the oil film and cause a bearing failure.



Not all engine builders agree this is necessary, but it should remove the sharp edges of the ferrite burrs leftover from the grinding process and leave what is called a "favorable" finish.



One rebuilder we spoke with says he grinds one direction and polishes the other to get as smooth of surface as possible. However, other engine builders we interviewed say they have not noticed any difference, no matter which way they polished the part.



The main goal in polishing any crankshaft or camshaft is to achieve the smoothest, flattest surface as possible. When cranks and cams are properly lubricated they turn and rotate very smoothly, which does two things: minimizes wear and more importantly it minimizes heat and fatigue. You want valleys for lubrication but also plateau peaks, not sharp peaks, to handle load.



So it is important to remember when you’re polishing that although it looks like art when you are finished, it really comes down to a science.





 
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https://www.mahle-aftermarket.com/na/en/support/installation-tips/crank-grinding-and-polishing.jsp
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Directions for crankshaft grinding and polishing
Crankshaft journal surfaces should be ground and polished to a surface finish of 15 micro inches roughness average Ra or better. Journals on highly loaded crankshafts such as diesel engines or high performance racing engines require a finish of 10 micro inches Ra or better.

The above is a simple straight forward specification which can be measured with special equipment. However, there is more to generating a ground and polished surface than just meeting the roughness specification. To prevent rapid, premature wear of the crankshaft bearings and to aid in the formation of an oil film, journal surfaces must be ground opposite to engine rotation and polished in the direction of rotation. This recommendation and examination of the following illustrations will help make the recommendation more clear.

Metal removal tends to raise burrs. This is true of nearly all metal removal processes. Different processes create different types of burrs. Grinding and polishing produces burrs that are so small that we can't see or feel them but they are there and can damage bearings if the shaft surface is not generated in the proper way. Rather than "burrs", let's call what results from grinding and polishing "microscopic fuzz." This better describes what is left by these processes. This microscopic fuzz has a grain or lay to it like the hair on a dog's back. Figure 1 is an illustration depicting the lay of this fuzz on a journal. (Note: All figures are viewed from nose end of crankshaft.)

crankfigure1.gif

The direction in which a grinding wheel or polishing belt passes over the journal surface will determine the lay of the micro fuzz.

In order to remove this fuzz from the surface, each successive operation should pass over the journal in the opposite direction so that the fuzz will be bent over backward and removed. Polishing in the same direction as grinding would not effectively remove this fuzz because it would merely lay down and then spring up again. Polishing must, therefore, be done opposite to grinding in order to improve the surface.

In order to arrive at how a shaft should be ground and polished, we must first determine the desired end result and then work backwards to establish how to achieve it. Figure 2 depicts a shaft turning in a bearing viewed from the front of a normal clockwise rotating engine. The desired condition is a journal with any fuzz left by the polishing operation oriented so it will lay down as the shaft passes over the bearing (Figure 2).

crankfigure2.gif

The analogy to the shaft passing over the bearing is like petting a dog from head to tail. A shaft polished in the opposite direction produces abrasion to the bearing which would be like petting a dog from tail to head. To generate a surface lay like that shown in Figure 2, the polishing belt must pass over the shaft surface as shown in Figure 3.

crankfigure3.gif

The direction of shaft rotation during polishing is not critical if a motorized belt type polisher is used because the belt runs much faster than the shaft. If a nutcracker-type polisher is used, then proper shaft rotation must be observed (Figure 4). Stock removal during polishing must not exceed .0002" on the diameter.

crankfigure4.gif

Having determined the desired surface lay from polishing, we must next establish the proper direction for grinding to produce a surface lay opposite to that resulting from polishing. Figure 5 shows the grinding wheel and shaft directions of rotation and surface lay for grinding when viewed from the front or nose end of the crankshaft. This orientation will be achieved by chucking the flywheel flange at the left side of the grinder (in the headstock). Achieving the best possible surface finish during grinding will reduce the stock removal necessary during polishing.

crankfigure5.gif

The surface lay generated by grinding would cause abrasion to the bearing surfaces if left unpolished. By polishing in the direction shown in either Figure 3 or 4, the surface lay is reversed by the polishing operation removing fuzz created by grinding and leaving a surface lay which will not abrade the bearing surface.

Nodular cast iron shafts are particularly difficult to grind and polish because of the structure of the iron. Nodular iron gets its name from the nodular form of the graphite in this material. Grinding opens graphite nodules located at the surface of the journal leaving ragged edges which will damage a bearing. Polishing in the proper direction will remove the ragged edges from these open nodules.

All of the above is based on normal clockwise engine rotation when viewed from the front of the engine. For crankshafts which rotate counterclockwise, such as some marine engines, the crankshaft should be chucked at its opposite end during grinding and polishing. This is the same as viewing the crank from the flanged end rather than the nose end in the accompanying figures.

Unlike many engine bearings available today, Clevite engine bearings utilize a superior Clevite TriMetal™ material design. Stamped "Clevite®," this design incorporates the strength of a copper-lead alloy layer on a steel back and finally, a precision electroplated white metal "babbitt" third layer. TriMetal™ is an ideal bearing design producing good to excellent characteristics when judged for conformability, embedability, slipperiness and fatigue resistance.

We constantly monitor the function and operation of our full line of bearings, staying in touch with any changes or developments that new engines may require. And that translates into bearings that are better for your engine. If you're looking for the engine bearings that set the standards, specify Clevite®. Because you won't settle for second best.

https://goodson.com/collections/crankshaft-polishing-belts


CRANKSHAFT JOURNAL FINISH BY KEN BARTON OE’s in some cases use two and three step Micro-polishing process’s starting with a large size particle (grit) and then stepping down in grit size to achieve the surface specification needed. OE’s have an advantage over engine rebuilders because they manufacture crankshafts in large lot runs, but as engine rebuilders, most often only have single or small lot runs. To accommodate the smaller production volumes and many different varieties of crankshafts - some shops use the power belt Micro-polishing process. This process is good on improving the surface finish, however, it has limited control over geometry characteristics or consistency for the process. Machines that use the OE’s type Micro-polishing process were developed to accommodate the rebuilder and performance Micropolishing needs. The machines are designed to be flexible, quick change over to various crankshaft journal widths, diameters, strokes, maintains or improves geometry, reduces operator involvement and provides a constant Micro-polishing process. This equipment can also consistently Micro-polish the fillet radius in tangential filleted crankshafts (eliminating the line at the point of tangent). A special abrasive film with serrated or scalp edges is used and it allows the abrasive film to go into and up the tangential radius without breaking. Undercut fillet radius crankshafts generally are deep rolled burnished. This strengthens this area and should not be polished or damaged in any way. Polishing or damaging this area will cause stress risers. The abrasive film spans over the undercut fillet with the equipment mentioned above and eliminates oil hole washout. Abrasive film cost per crankshaft average 20 to 30 cents for the above-mentioned equipment. Today, in addition to measuring the surface finish, many other measurements are made. Two of the basic measurements are surface finish “Ra” and bearing ratio “Tp”. • Basic definition of surface finish “Ra” — Average surface roughness using measurements of the peaks and valleys from the grinding process. • Basic definition of bearing ratio “Tp” is the ratio (expressed as a percentage) of the length of the bearing surface at any specified depth in the evaluation area. Bearing ratio results are available for profile data (Tp) and surface area (Stp). There are numerous other measurements such as Rz, Rpk, Rvk, etc. Micro-polishing has been available to the engine builder for some time now; more shops are using it as time goes on as they become aware of its benefits. Many production engine builders and crankshaft suppliers have been using Micro-polishing for years. Premature bearing wear on crankshafts may be created by a number of conditions, below is a list to consider. • Improper mating part materials • Crankshaft bearing surface finish • Crankshaft bearing geometry • Improper clearances • Improper maintenance • Improper preparation before assembly into engine block • Oil Contamination Although any of these factors may be the underlying cause of bearing failure, our understanding (from customer interviews) is that the three leading causes are: 1. Improper preparation prior to installation 2. Improper or no controlled Micro-polishing of bearing surfaces and thrust walls 3. Improper engine maintenance Failure to properly Micro-polish the journals may leave the crankshaft with a rough surface, and tapered, or wavy bearings. Failure to Micro-polish may also leave the journals with out of round surfaces and wash out of the oil holes that may also contribute to rapid bearing wear. The proper controlled Micro-polishing process will help correct any or all of the following conditions that may contribute to premature bearing failure. The controlled Micro-polishing process will also eliminate ferrite caps found in nodular iron crankshafts. This is another common cause of premature bearing failure. Geometry Improper bearing geometry conditions such as concave, convex, taper, out of round, and combinations of these conditions will create conditions that prevent the journal from mating evenly with the mating bearing.
crankf.png

http://www.engineprofessional.com/articles/EPQ118_64-70.pdf
 
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All Good stuff Grumpy.
A few months back I was looking around for a Home affordable dial bore gauge kit to read 1.000" to 5.000" and accuracy down to .0001" - 1/10 thousands of an inch.
Not easy to find.
Most are .001" or .0005" accuracy. Fine for most most checks but the Main caps torqued down no bearing shells check the line bore size and same with connecting rods checking the big end size no bearing shells installed.
 
I have a Starret inside micrometer set & Vintage Kent Moore Starret made dial bore gauges Mechanics used.

And a Digital Mitoya 3 anvil dial bore gauge, Think 1-2 inch. Its so touchy I seldom use it. Bob made me a ring standard to use to calibrate many years back checked at his work Toolroom with inspection guys.
 
I have oil feed hole mods done on my Pontiac crankshafts.
Believe it helps at high rpms.
Only trust my Bud Steve to do it.
Has to be done Free hand with an air die grinder and ball stone.
One slip and crank is ruined.
All mains and all rod journals get it.
 
Buy a Crower Billet 4340 Crank it's not needed.
Straight shot oil system standard.
Price came down. $4000 cash now Pontiac V8.
Used to be $8500- 10k.
 
GRUMPY?
whats the cost to polish a crank to undersize journal size

RELATED INFO

http://garage.grumpysperformance.co...ned-undersized-and-polished.15934/#post-95927

http://garage.grumpysperformance.com/index.php?threads/bearing-clearances.2726/page-2#post-88656

http://garage.grumpysperformance.co...guess-on-clearances-and-journal-surface.9955/

http://garage.grumpysperformance.com/index.php?threads/crankshaft-journal-surface-finnish.2728/


http://garage.grumpysperformance.com/index.php?threads/scat-cranks-related-info.10930/#post-74729

http://garage.grumpysperformance.co...haft-journal-surface-finnish.2728/#post-72043

http://garage.grumpysperformance.co...a-scat-rotating-assembly-be.11495/#post-52962

http://garage.grumpysperformance.co...pes-of-crankshaft-steel.204/page-2#post-46231


that cost obviously depends a great deal on the shop you deal with,
how badly the crank journal(s) are damaged,
and if you need one or more or all the rod and/or crank bearing journals resized and polished,
and how accurately the machine shop work is done,
and of course how busy they are and strapped for cash flow.
minor surface scratch damage can be corrected in some cases with 600 grit,
then swap to 1200 grit, wet/dry sand paper and,
use a leather belt and a marvel mystery oil lube,
most local shops charge about $50-$70 to cut/polish a single bearing journal, But its been my experience , that most shops want to turn ALL rod journals or both the rod and main journals down to a uniform under size standard of .010-.020 undersize if they take the job, and charge about $375-$450,
as the set-up time is a big factor so they want to do the whole crank to boost the total bill and also reduce the chances you stick the wrong bearing size on a journal, and most shops will want to sell you a full set of matched bearings and other related machine work
making purchase of a New replacement crank a VALID FINANCIAL OPTION IN MANY CASES



https://www.enginebuildermag.com/19...nals-on-the-crankshaft-are-properly-polished/

https://www.mahle-aftermarket.com/na/en/support/installation-tips/crank-grinding-and-polishing.jsp

https://www.enginelabs.com/news/video-do-it-yourself-crankshaft-polishing/

Crankshaft journal surfaces should be ground and polished to a surface finish of 15 micro inches roughness average Ra or better. Journals on highly loaded crankshafts such as diesel engines or high performance racing engines require a finish of 10 micro inches Ra or better.


The above is a simple straight forward specification which can be measured with special equipment. However, there is more to generating a ground and polished surface than just meeting the roughness specification. To prevent rapid, premature wear of the crankshaft bearings and to aid in the formation of an oil film, journal surfaces must be ground opposite to engine rotation and polished in the direction of rotation. This recommendation and examination of the following illustrations will help make the recommendation more clear.

Metal removal tends to raise burrs. This is true of nearly all metal removal processes. Different processes create different types of burrs. Grinding and polishing produces burrs that are so small that we can't see or feel them but they are there and can damage bearings if the shaft surface is not generated in the proper way. Rather than "burrs", let's call what results from grinding and polishing "microscopic fuzz." This better describes what is left by these processes. This microscopic fuzz has a grain or lay to it like the hair on a dog's back. Figure 1 is an illustration depicting the lay of this fuzz on a journal. (Note: All figures are viewed from nose end of crankshaft.)

crankfigure1.gif

Figure 1
The direction in which a grinding wheel or polishing belt passes over the journal surface will determine the lay of the micro fuzz.


n order to remove this fuzz from the surface, each successive operation should pass over the journal in the opposite direction so that the fuzz will be bent over backward and removed. Polishing in the same direction as grinding would not effectively remove this fuzz because it would merely lay down and then spring up again. Polishing must, therefore, be done opposite to grinding in order to improve the surface.


In order to arrive at how a shaft should be ground and polished, we must first determine the desired end result and then work backwards to establish how to achieve it. Figure 2 depicts a shaft turning in a bearing viewed from the front of a normal clockwise rotating engine. The desired condition is a journal with any fuzz left by the polishing operation oriented so it will lay down as the shaft passes over the bearing (Figure 2).

The analogy to the shaft passing over the bearing is like petting a dog from head to tail. A shaft polished in the opposite direction produces abrasion to the bearing which would be like petting a dog from tail to head. To generate a surface lay like that shown in Figure 2, the polishing belt must pass over the shaft surface as shown in Figure 3.

crankfigure2.gif

Figure 2
crankfigure3.gif

Figure 3
The direction of shaft rotation during polishing is not critical if a motorized belt type polisher is used because the belt runs much faster than the shaft. If a nutcracker-type polisher is used, then proper shaft rotation must be observed (Figure 4). Stock removal during polishing must not exceed .0002" on the diameter.

Having determined the desired surface lay from polishing, we must next establish the proper direction for grinding to produce a surface lay opposite to that resulting from polishing. This figure hows the grinding wheel and shaft directions of rotation and surface lay for grinding when viewed from the front or nose end of the crankshaft. This orientation will be achieved by chucking the flywheel flange at the left side of the grinder (in the headstock). Achieving the best possible surface finish during grinding will reduce the stock removal necessary during polishing.

crankfigure4.gif

Figure 4
crankfigure5.gif

Figure 5
The surface lay generated by grinding would cause abrasion to the bearing surfaces if left unpolished. By polishing in the direction shown in either the figure 3 or 4, the surface lay is reversed by the polishing operation removing fuzz created by grinding and leaving a surface lay which will not abrade the bearing surface.


Nodular cast iron shafts are particularly difficult to grind and polish because of the structure of the iron. Nodular iron gets its name from the nodular form of the graphite in this material. Grinding opens graphite nodules located at the surface of the journal leaving ragged edges which will damage a bearing. Polishing in the proper direction will remove the ragged edges from these open nodules.


All of the above is based on normal clockwise engine rotation when viewed from the front of the engine. For crankshafts which rotate counterclockwise, such as some marine engines, the crankshaft should be chucked at its opposite end during grinding and polishing. This is the same as viewing the crank from the flanged end rather than the nose end in the accompanying figures.


Unlike many engine bearings available today, Clevite engine bearings utilize a superior Clevite TriMetal™ material design. Stamped "Clevite," this design incorporates the strength of a copper-lead alloy layer on a steel back and finally, a precision electroplated white metal "babbitt" third layer. TriMetal™ is an ideal bearing design producing good to excellent characteristics when judged for conformability, embedability, slipperiness and fatigue resistance.


We constantly monitor the function and operation of our full line of bearings, staying in touch with any changes or developments that new engines may require. And that translates into bearings that are better for your engine. If you're looking for the engine bearings that set the standards, specify Clevite®. Because you won't settle for second best.



 
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