SBC Main Bearing Studs torque stretch



Is there something similar to the subject on the following link. ... tretch.php. Finally, someone came up with torque angle values for connecting rods. Sure would be nice to see the same for SBC Main Bearing Studs. Torquing to an angle takes away all the ambiguity of what torque is to be applied to connecting rod bolts. I wish I had this data when building my 383 stroker. Now, when building the bottom end, using a bolt stretch tool and a torque angle tool and measuring connecting rod clearances when properly torqued off the engine and compared to the appropriate journal on the crankshaft. Would be nice to do the same for the main bearing caps and achieve the lowest amount of crankshaft rotating torque value possible. Same goes with adding connecting rods and pistons, without rings, one at a time and measuring amount of torque to rotate assembly. Thinking about using electric starter and measuring the amount of current at each step of the build. Your comments and experiences PLEASE!


Staff member
rsicard said:
Would be nice to do the same for the main bearing caps and achieve the lowest amount of crankshaft rotating torque value possible. Same goes with adding connecting rods and pistons, without rings, one at a time and measuring amount of torque to rotate assembly. Thinking about using electric starter and measuring the amount of current at each step of the build.

Hope you don't mind if I jump in here and make a comment.

I don't think the amount a fastener is tightened will make any difference in the torque to rotate the crankshaft. It will be more a function of main bearing bore alignment, crankshaft straightness and the lube you use on the bearing.

My first thought when reading your comments was ...... how do you know when to start measuring the angle, but I see from the article that is what the "Torque and Angle" column is about.



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Staff member
from an engineering stand point , the better aftermarket (LIKE ARP) rod bolts are cut to a rather precise length and you can get a rod mic on BOTH ends of the bolt to MEASURE rod stretch, you can,t be as precise with a stud with one end located deep inside a threaded hole anchored in the block with only access to the one exposed end, of course the object is to minimize the main cap and block distortion while maximizing the clamp force and minimizing main cap movement, read the links below, and just as a point of interest Ive found use of splayed main caps and main cap dowels, and the thicker , better quality aftermarket blocks, like you can get from DART rather useful





obviously checking the crank as it sits and rotates in the bearing saddles before the main caps are installed with a dial indicator and stand will be useful in determining if the cranks bent or the bearing saddles are miss aligned




viewtopic.php?f=50&t=2138&p=5765&hilit=torque+angle#p5765 ... _rods.aspx




viewtopic.php?f=50&t=989&p=1744#p1744 ... ch-part-1/

the new ICON line looks decent ... ch-part-2/
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My objective is the least friction in the rotate/recip assembly through precision and proper torquing. I doubt that the machine shop that I used checked the straightness of the crankshaft and of the main bearing bores. He did line hone the mains and I don't know what type of tooling he used to check the precision of his work. It would be interesting to use a laser on the main bearing saddles with bearing inserts to see just how straight and true they are. Also would be interesting to do a run-out check of the crankshaft to get an idea of how straight the mains are on it. Then torque all main caps with inserts and dimension all of them for clearances. Once all of this is done properlly, have a bar machined and polished with .245 inch diameter and set in the front and rear main bearing saddles then torque them to spec with inserts. Then twist the test bar to see how much friction there is. Then one at a time add-in another main bearing with insert and re-torque and check for friction again and just keep the process going to discover if anything is wrong with clearances or alignment.

I consider torque to an angle to be the most precise way to go.


Torque to Angle is not nearly precise as you may think.
ARP & CROWER makes the Best fasteners bar none.
Torque to angle was developed for high speed automated machine assembly.
I worked at Caterpillar back in 2005 for a 1 year stint.
The Torque to angle machines broke down at least 3 times a week on my line.

Who is going to machine the main bearing saddle bar for You ?
It must be precision ground.
Dumore Tool Post grinder. 1 hp drive model.
Must hold a tolerance 1/10,000 of an inch over a 24 inch span.
Not many are competant to make.
My friend Mopar Bob is.
Shop rate to make would be $700 - $1k.
But why ?
How much Horsepower are you going to make ???
You shooting for 2,000+ Hp ?

.043 " Inch piston ring set better.
If your real good.
You know what to use exact. Elimiate all oil rings.
80 % of engine rotating drag comes from oil rings.
Not free floating crankshaft in a pressure fed hydrofluid bearings.

Wasting time.




Staff member
its common for a used block to require the main caps to be line honed if you want the bearing saddles to be uniform and strait.
obviously having a few tools tho precisely measure any problems helps , a magnetic clamp on stand and a digital meter will be useful




STAND ... -5645.html






related info ... shaft.html

viewtopic.php?f=53&t=852&p=21611&hilit=crank+measure#p21611 ... ewall.html ... g_install/





viewtopic.php?f=53&t=3449 ... shaft.html

Ive occasionally been asked what you can do too reduce the slack in the timing chain if your blocks been line honed,
to straiten the main bearings and that resulted in a slightly closer crank to cam center-line distance,
that results in a slightly increased slack in the stock timing chain sets.
a negligible amount of metal is generally removed from the main bearing saddles in the block, they usually try very hard to minimize that, metal removal so standard parts still fit,during a line hone , but they do sell slightly tighter timing chain sets to correct excess slack if that's required.


Timing Chain and Gear Set, Original True Roller, Double Roller, -0.005 in., Iron/Steel Sprockets, Chevy, Small Block, Set
for line honed blocks where the crank is .005 closer to the cam
for line honed blocks where the crank is .010 closer to the cam
Timing Chain and Gear Set, Original True Roller, Double Roller, -0.010 in., Iron/Steel Sprockets, Chevy, Small Block, Set

the instructions below I grabbed off a different site might be helpful here

"Points to note

Don’t hammer on the bearings you should be able to press them all in by hand.
Ensure the bearings are fitted correctly with oil feed holes in the block and bearings lining up.
Ensure the bearings and crankshaft have a light smear of oil over them before installing the crankshaft.

Part 2: Step-by-step instruction

Check bearing size
If the main journals of the crankshaft for this motor were cut undersize, make sure you get new main bearings that are the same amount oversized.
Before you open them, double check the new parts labels to make sure they are the correct type and size.
Fit main block bearings
Wipe out the saddles of the block and then press the bearings into place by hand. There is a groove in the bearing saddle of the block and a Tang on the back of the bearing that should fit into the alignment grove in the block. Don't hammer on the bearing, you should be able to press them all in by hand. It's a simple process, you just push on both sides alternately to seat them.
Make sure that the bearing halves that you put in the block are the ones with the oil feed holes in them, and check that the oil holes in the block line up with all the holes in the bearings.
Install the crankshaft
Put a drop of oil on each bearing and wipe it very thin and evenly. It is not a good idea to lay a crankshaft on totally dry bearings.
Every engine has one main journal that will have a Thrust Bearing installed in it. This bearing is the one that will limit the forward or backward movement of the crankshaft in the block. Make sure to wipe some oil on the thrust surface of the thrust bearing as well. The crankshaft will be rubbing on the thrust face of the bearing at these two points.
Clean off any dust that might have collected on the crankshaft journals. Ask for some lifting help if you need it, and then gently set the crank into the block. If you drop it, the bearings might be fatally damaged so get a good grip and take it slow.
Install crankshaft clearance gauge
Now you need to check the actual clearance between the crank journals and the bearings. This is a critical measurement. For the time being, we're only dealing with these three main journals. Make sure the throws, which are these parts of the crankshaft, are out of the way so the crankshaft sits in the block like this. That will let us install these three main caps with our checking tool and still be able to tap on the bolts to remove the caps without rotating the crank.
For a stock rebuild, most engines need a very small but very precise clearance on the main journals. You can look up the main bearing clearance specifications in your repair manual.
The bearing suppliers usually include a clearance gauge with new bearings, but these are also available at parts stores.
Cut strips of this gauge that are the same widths as the main journals. Don't tear them with your fingers, as you could flatten the strip and get a bad reading. Inside the wrapper is a little sliver of plastic. That's the gauge. Lay one strip on top of each of the main journals of the crank. Clean the caps and install the lower bearing halves – remember, the block is upside down now and the lower halves are the ones that go in the caps and don't have oil holes.
It's helpful to use a thin film of petroleum jelly on the bearing where it will touch the plastic strip. This will keep it from sticking to the bearing. As you put the caps in their places, follow any stampings that you made during disassembly so they are in the correct place. If you need to tap the caps in place to get them to seat, be very careful not to tap down too hard as this might squash the plastic and give a false reading.
Torque three main cap bolts
Every bolt that goes in the engine should have some kind of lubricant on it before it goes in. For this procedure, the main cap bolts get engine oil. When all the bolts are in and hand tightened, you'll need a Torque Wrench to finish tightening them to whatever specification is listed for your main caps.
There are many different kinds of torque wrenches available, but one common rule. Never simply set the wrench to the full torque spec and tighten the bolt to the maximum during the first pull. The right way to use all torque wrenches is to work up to the full torque specification in at least three equal increments.
For example, the specifications for this block say that these bolts should be torqued to 95 Newton meters or 70 foot pounds. Set the wrench to one third of that amount and torque all the bolts. Then set the wrench to about two thirds of the final amount and torque again. The settings don't have to be exact thirds, just approximate. Then set the wrench to the final torque specification and finish tightening.
If you have 4-bolt main caps tighten the inner bolts first, then the outers bolts. Be careful not to bump the crankshaft or rotate it at all as you do this or the readings on the plastic strips will be inaccurate.
Once they are tightened to the correct torque, unscrew them, but again, be very careful not to move the crank accidentally with a tool or with your hand. When the bolts are fully unscrewed, lift them up and tap on them gently to loosen the cap.
Measure bearing clearance
The squashed piece of plastic gauge material should be stuck to the main journal or to the bearing in the cap. A measuring strip came with the gauge. Hold it next to the squashed plastic. Make sure you are looking at the right side of the measure, because there is usually an Imperial side and a metric side. The number next to the strip which is the closest match will be the size of the main bearing clearance. This measurement needed no expensive micrometers or particular skill, and it indicates the clearance with all the actual parts installed in place.
This result is exactly what it was supposed to be, which shows that our new bearings are a perfect fit. Clean off the flatten piece of plastic, bit don't worry about getting it all off completely, as it will dissolve in oil.
Repeat the measuring process
Rotate the crank so that the other throws are out of the way and repeat the process for the rest of the journals. . After you torque in three increments, remove the caps and check the last clearances. If the main bearing clearances are correct, lift the crank out, but keep it nearby.
Reinstall the crankshaft
Put some lubrication on the bearings then carefully lower the crank back into the block. Put some oil on the bearing shells in the caps too. Refer to the marks that you stamped on the caps to make sure the right ones go in the right place.
Now you can spin the throws out of your way as you torque the bolts, this time it should be a quicker and easier process. Toque all of the regular main caps first, and leave the cap that has the thrust bearings in it to last.
Align the thrust bearing
When you get to the cap with the thrust bearing, you need to seat the bearing before you torque it. Never directly hammer on a crankshaft, but put a hammer or block of wood against the crank flange on the back and tap it with another hammer.
This will make sure that the upper and lower thrust bearing shells are lined up with each other. Now you can torque the cap that has the thrust bearings in it.
When all the caps are torqued, the crank should be very easy to turn by hand. You shouldn't feel any binding or tight spots."

thrust bearing clearances is usually supposed to be in the .003-.008 range for a small block chevy , with .006-.008 preferred, if the clearance is too tight the forward facing bearing face of the bearing is usually sanded with 600 grit paper on a sheet of flat window glass with diesel fuel on the sand paper ,(move the bearing face in a figure (8) pattern, on the wet sand paper to sand off extra clearance,) to get a couple thousands extra required then carefully cleaned and re-tested for crank end play clearance, if its to loos the cranks usually welded up and re-machined back down to have less clearance with a near mirror surface finish on the bearing thrust surface on the crank, but on a stock cast sbc crank, unless you have some kind of emotional investment in the crank it's almost always cheaper to buy a new crank, and yes thats why you check clearances BEFORE you pay to balance the rotating assembly.
you can probably get by on a street car installing the crank with its current thrust bearing clearance but the result is likely to rapid dear on the bearings, so Id advise against it.
THERE may be over size thrust bearings available, but Ive never seen those locally or needed to look for them

KING BEARINGS LISTS THEM IN SEVERAL SIZES, WHY NOT CALL THEM, if they have the correct size youll still need to polish the crank matched surface to prevent further rapid wear

King Engine Bearings, Inc.
371 Little Falls Road, Suite 5
Cedar Grove, NJ 07009

Phone: 1-973-857-0705
Toll Free: 1-800-772-3670
Fax: 1-973-857-3228

related info

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Staff member

rsicard said:
Same goes with adding connecting rods and pistons, without rings, one at a time and measuring amount of torque to rotate assembly.
I think he rsicard maybe doing this as a mental exercise and trying to isolate the problem to the rotating assembly without the rings.


I am looking for a process to ensure that the crankshaft and main bearings are straight and true such that once the main bearings are clearance properly, properly torquing the crankshaft will result in the crankshaft that will spin with a minimum of resistance. If need be, I will take the crank to a coordinate measuring machine to make certain it is straight and fix it if bent. Want to try a laser on the main bearing saddles with inserts after clearancing them to make certain the bearing saddles are precisely in line. I wonder if the machine shop that I use as a VERY STRAIGHT test bar that can be bolted into the main bearing saddles to test for straightness.

I use main bearing studs and cylinder head studs as they have a much more true torque applied. Also found that even using ARP studs, torque and re-torque at least three time to wear off the rough spots on the stud and nuts. I have read almost every article written by Smokey Yunick and David Vizard and try to use the best of their ideas for putting an engine together.

I have rebuilt several engines in my airplanes and ground vehicles all with success. I am not a beginner in these matters.
hy grumpy , i was reading this post, whats the specification for crankshaft straightness reading. for a small block chevy . ( 350) . i measured my crank shaft for run out in the block saddles, and the reading was .001" now is that within limits , thanks


Staff member
Short answer .001 is going to be about normal on most SBC rebuilds and not a problem in most cases, in fact factory specs allow a good deal more

Just what is a Runout?
basically you level the block on the engine stand, you verify with a strait edge the blocks main journals appear to be strait and level, you then insert the outer two main bearing upper bearing shell halfs in the block,then you, first seat the crank in the end two main journals,on the upper bearing shells lubed with assembly lube, you set your dial indicator with a solid stand so you can accurately measure on each of the three inside main crank journals as they rotate , MOST GUYS ONLY CHECK THE CENTER JOURNAL, as you carefully watch and manually rotate the crank,in those two end bearings shells. done individually to test each of those three locations,and slowly rotate the crank looking for an indication the cranks bent, indicated by the center three main journals movement. I generally try hard to keep that in the .001-.0015 range, and I certainly would not panic it it measured .002

obviously checking the crank as it sits and rotates in the bearing saddles before the main caps are installed with a dial indicator and stand will be useful in determining if the cranks bent or the bearing saddles are miss aligned

How to Measure crank shaft Straightness
WATCH VIDEO ... n-out.html

What the heck are we measuring when we measure run-out? The run-out measurement described in Lycoming's overhaul manual is a circular runout measurement. Another type of run-out, Total run-out, measures something different and is not described here. When one says run-out it is assumed to mean circular run-out.

Circular run-out is neither a dimension nor a clearance but a displacement measurement that encompasses roundness (concentric) and position; a composite measurement. Being a composite measurement means that there are both form (roundness) and off-center (position) that make up our reading. Off-center for example might be because the crankshaft is bent. Something undesirable. Several automotive engine build books incorrectly describe run-out as the amount the crankshaft is bent. It could be or it might not be. It could be a little bent and a little bit not round. Or it could be straight but not round. We really don't know what the problem is. All we can say is that circular runout is so much. This means that our datum axis is displaced so much or the datum axis has so much eccentricity.

Lets assume for a minute that both roundness and position are perfect, but as we rotate the shaft in the Vee-block the shaft walks up the side of the Vee block ever so slightly. We have not measured a feature or dimension of the crankshaft but the movement of the shaft up the side of the Vee-block.2 Lets assume again our perfect shaft but the table sags slightly from the weight of the crankshaft. We have now measured the amount of sag. So just because we get a reading that is non-zero we cannot assume that this is attributable to the crankshaft. Maybe these other influences are just enough to throw the measurement past the specification. We want to be careful that we don't reject an expensive crankshaft based on table sag!





main cap studs, studs are NOT torqued into the block!

studs are screwed into the block for the full thread length then backed out 1/2 turn,
STUDS are installed through the main caps, before the nuts and washers are installed,
I generally oil the threads on the lower stud threads in the block,
but no loads are applied to the studs until the threads in the block are full length engaged,
into the block and the washers & nuts on the studs are tightened.

How to Install ARP Main Cap Studs - Hot Rod Engine Tech

Serious race engine builders mostly use high strength ARP studs to anchor the main caps. Studs provide a more even clamping force with higher tensile strength than most bolts and they are less highly stressed in the block ...

How to Install ARP Main Cap Studs​

Serious race engine builders mostly use high strength ARP studs to anchor the main caps.
Studs provide a more even clamping force with higher tensile strength than most bolts and they are less highly stressed in the block .

1. Clean and inspect ALL threads in the cylinder block thoroughly. After initial tank cleaning, dry the block and inspect threads closely. Chase the threads with the appropriate size ARP thread chaser if necessary.
To prepare the threaded holes select a small stiff bristle nylon cleaning brush as found in engine brush kits available from online retailers.
We prefer to scrub the main cap bolt threads with a brush and brake cleaner and then blow them out with air to get them spotlessly clean prior to assembly. At this point you should also ensure that the main cap mounting surfaces are spotlessly clean and free of any nicks, burrs or other contamination. This step is important to ensure perfect seating of the main caps.
3. Clean and inspect ALL studs and verify all dimensions. Remove all shipping lubrication from the studs until they are squeaky clean.
4. Screw the studs into the appropriate holes HAND TIGHT ONLY! While not specified by the manufacturer, we prefer to brush a very thin coating of ARP Ultra-Torque fastener assembly lube on the threads. Do not over-tighten the studs in the block.
Note: If permanent mounting of the studs is desired, Loctite may be applied to the threads.
If you do this the fasteners must be final torqued before the Loctite sets up.

main cap stud install

5. Install the main caps and check for proper fit and alignment.
Splayed bolt main caps require outer stud installation after each main cap is installed.
Install the inner studs and use them as a guide for the main cap.
Tap the cap into place and then install the outer studs. (USE A DEAD BLOW MALLET)
6. Use a small application brush to coat the stud threads and washers with assembly lube and install the nuts finger tight.
Whether using ARP fasteners or others,
we recommend ARP Ultra-Torque fastener assembly lubricant to ensure consistent torque readings.
Lubing with regular motor oil is discouraged due to inconsistent clamping forces. (THIS IS REFERING TO THE UPPER FINER THREADS< NOT THE
7. To apply the proper preload to the studs follow the manufacturer’s recommendations.
Torque the nuts in three even steps until you reach the recommended torque spec.
Note: clamping forces will change when installing new studs. Check the main bearing housing bores for proper size and out of round condition. In most cases align honing the mains with the new studs properly torqued will be necessary to ensure proper fit and clamping forces.
Editors note: If you found this article helpful, please click HERE to let them know and to order you copy of their 2013 catalog.



O.E.M. factory bolts use the 110 lb torque
ARP main cap bolts and STUDS CAN and frequently DO require a different torque
splayed aftermarket main caps generally use smaller diameter outer bolts that require less torque



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