causes of bearing failure

[grumpyvette]

its well worth reading thru the links posted here carefully

Viscosity/centistoke

occasionally I get asked questions ,concerning terms or concepts that I assumed were common knowledge. ok lets start with the basics, oil flowing over the moving surfaces in any engine is used too, absorb and transfer heat away from, and separate and prevent physical contact between moving...

garage.grumpysperformance.com

theres at least a few hours of very worth while , and quite useful reading in this thread and links that will prevent you wasting time and money, keep in mind the sub links contain a huge wealth of additional info youll need
what seems to be over-looked in many engine builds is simply the fact you'll almost always DEEPLY regret jumping into the engine build with both feet and waving your check book as you sink ever deeper into piles of parts receipts and machine shop bills, rather than stepping back with a legal pad, and a calculator and listing in minute detail exactly what you want to accomplish, and taking the time and effort too list and check out in detail what each machine shop procedure costs, why its required and how much each components costs, what your options are and how each component will add too or benefit the completed combo (or in some cases cause you time and grief)
stepping back and thinking things through in detail and listing the cost and potential problems and finding the solutions BEFORE you dive into the process may be a lot less fun, but in the long term its sure to cost less and result in a far better finished project!

you might be amazed at what a couple hours research into the subject will do to help you build a much more durable engine, and actually reading thru links and sub-links and asking questions helps a great deal
http://www.engineparts.com/publications/CL77-3-402.pdf

viewtopic.php?f=54&t=3519

http://www.stealth316.com/misc/clevite- ... ooving.pdf

http://kingbearings.com/files/Engine_Be ... erials.pdf

http://www.bracketracer.com/engine/mains/mains.htm

http://garage.grumpysperformance.co...k-after-a-cam-lobe-rod-or-bearings-fail.2919/

http://garage.grumpysperformance.co...oil-passages-and-improved-oil-flow-mods.3834/

viewtopic.php?f=54&t=120&p=150#p150

http://www.circletrack.com/enginetech/c ... ce_basics/

http://engineparts.com/techbulletins/CL77-1-205R.pdf

http://www.bobistheoilguy.com/bearingwe ... alysis.htm

http://www.mahleclevite.com/publications/EB-40-07.pdf

Ive generally found the H-series bearings are the best choice

one factor to keep in mind is that rods typically have a side that rides against its matched companion and a side thats BEVELED for clearance on the crank journals radias EXAMPLE

notice the top rods non-beveled side that faces the matching rod is up, but on the lower rod the the beveled side that faces the crank counter weight is up on the lower rod

failure to clean out the oil passages in the block and crank journal cross feed oil holes, resulted in trapped debris being flushed out and scoring the bearings during the test fit process in these bearings, an easily avoided but very common screw-up after a cam or bearing fails and your forced to do a ring, cam,lifter, and bearing replacement
just keep in mind that you'll need to very carefully blend and smooth and carefully clean,the edges of the beveled area where the oil port feeds the bearing surface with some 600 grit sand paper so the oil flows well and theres no edges to cause bearing wear issues or crud left from the process that would get embedded in the bearings.

watch this video
http://www.youtube.com/watch?feature=pl ... dEFGJqpCMY
http://www.enginebuildermag.com/Article ... o_bad.aspx
MORE USEFUL INFO

BE 100% SURE that the oil pump bolt or STUD doesn,t protrude past the inner main cap surface , because if it bears on the rear main bearing shell it will almost always result in a quickly failed rear bearing
MAJOR CAUSES OF PREMATURE BEARING FAILURE
Dirt ......................................... 45.4%
Misassembly .......................... 12.8%
Misalignment .......................... 12.6%
Insufficient Lubrication.............11.4%
Overloading .............................. 8.1%
Corrosion ................................ .3.7%
Improper Journal Finish ............ 3.2%
Other ....................................... .2.8%

in a properly set up block a pressurized oil film supports the cam and main bearings
you would most likely be amazed at the metallic crud a few high temp magnets , and shrapnel screens can trap and prevent from getting to your oil pump and bearings, or the amount of crud a decent oil filter traps once its passed thru the oil pump, especially if the oil filters equipped with a strong magnet, but changing your filter and oil on a frequent basis and assembling your engine with the correct clearances helps a great deal, any time you use a block on a new engine build youll need to remove all the oil passage plugs an rod out the oil passages with a rifle bore brush and a high pressure pressure cleaner and replace the gallery plugs, and cam bearings.
if you've had a cam wipe a lobe or a bearing fail its an EXCELLENT IDEA to replace the cam bearings and use a rifle bore brush to remove metallic crud from the blocks internal oil passages because theres an excellent chance they have trapped metallic crud in them

viewtopic.php?f=51&t=1458&p=3265&hilit=shrapnel#p3265

viewtopic.php?f=54&t=120&p=867&hilit=+magnets#p867

viewtopic.php?f=54&t=2187

viewtopic.php?f=54&t=2080

viewtopic.php?f=54&t=65

viewtopic.php?f=54&t=64


http://www.appliedindustrial.com/base.cfm?page_id=3549
from chevy high performance mag

Common Causes of Bearing Failures

There are many causes of bearing damage. It is not always easy to determine the exact cause, but most bearing failures can be attributed to one or more of the following major causes:

Foreign matter: One of the most common sources of trouble in bearings is wear and pitting caused by foreign particles. This could be in the form of dirt, abrasive grit, lint, dust, steel chips, etc.

Improper mounting: Bearings should be mounted with a press fit on the rotating ring. Generally, the shaft rotates and the inner ring is mounted with a press or interference fit.

1. Mounting bearings on shafts by applying blows or pressure to the outer race will usually cause denting (true brinell).
2. Loose shaft fit – rotation of the shaft within the inner ring can produce heat and small loose particles of metal that will eventually get into the bearing, causing wear.
3. Loose housing fit – damage similar to loose shaft fit.
4. Excessive tight fits – (shaft and housing) can cause rings to crack. Usually causes excessive internal preload because of the removal of internal clearance. Causes high operating temperature and premature failure.
5. Out of round housings – usually found in split housings where careful machining is necessary to obtain round housing. Causes localized overloading with abnormal wear on surfaces and retainer pockets. Early fatigue occurs in these areas.
6. Poor finish on the bearing seat – a coarse finish on the bearing seat will soon break down causing a loose fit condition, previously described.

Misalignment: A frequent source of trouble resulting in overheating and separator failure. Common causes are bent shafts, out-of-square shaft shoulders, out-of-square spacers, and out-of-square clamping nuts. Inspection of the raceways will show the ball track veering from one side to the other.

Vibration Brinell (False Brinell): Caused by the rapid movement of the balls in the raceway while the equipment is idle. Rolling elements quickly remove lubrication and, because there is not enough rotation of the bearing, fresh lubricant is not moved back into the spot. This means the bearing is sitting in one spot, devoid of lubrication, and the movement of the rolling elements wears away the metal. The indentations run axially across the races.

Electrical Damage (Fluting): When electric currents pass through a bearing, there is arcing and burning at the points between the races and the rolling elements where the current jumps the air gap. Pitting or cratering of a bearing is caused by relatively large charges of electricity.

A line of small burns along the line of contact of the rolling elements is caused by a low current constantly passing through the bearing. This fluting or grooving is formed on all parts as the current continues to pass through the bearing, and the contact points change as the bearing rotates. The steel melts in the affected zone. Electrical damage will cause early spalling and results in a noisy bearing which will have to be replaced.

Improper Lubrication: Lack of or improper lubrication generally causes overheating or excessive wear in the bearing. These conditions can result from insufficient lubrication, improper lubricants, complete absence of lubrication, or insufficient lubrication due to loss through leakage. Also to be considered is the breakdown of lubricants either by oxidation or exposure to atmospheric conditions.

Fatigue: Fatigue means the fatiguing of the metal in the components of the bearing. It is a result of stress reversals produced when rotating members create flexing of the metal. Fatigue develops due to the magnitude of the load and the number of times it is repeated. Actually, the rolling elements create a wave of metal in front of them as they roll. Thus, the metal in the components is alternately put in tension and then compression. This action eventually results in flaking of the metal.

Corrosion: The finely finished surfaces of ball and roller bearings are readily subject to corrosion by water, acids, and other agents. Corrosion is basically abrasive in nature and will account for excessive or abnormal wear in bearings. Common causes of corrosion include moisture, acid action, poor or broken down greases, poor wrappings, and condensation resulting from excessive temperature reversals.

Defective Sealing: This enables foreign material and contaminants to enter the bearing, causing wear.

High Temperatures: High temperatures frequently cause premature bearing failure, the nature of the failure being predicated on the temperature to which the bearing is raised and the grease with which it is lubricated. Mild temperature elevations may cause grease to bleed which reduces the efficiency of the lubricant. Under increasingly elevated temperature conditions, oxidation causes loss of lubricating elements and the formation of carbon. The carbon thus formed may lock or jam the bearing. High temperatures may also reduce the hardness of the metal causing early failure. High temperatures can cause loss of internal clearance and preloading results. Many bearing failures can be traced to dirt. Cleanliness is always a must.

Storage: Dampness (rust) - store bearings in a dry room.

 

[grumpyvette]

Eliminating The Low Oil Pressure Gremlin


This solution has been the most effective in solving a problem that seems to creep up for every engine builder everywhere.

By Roy Berndt

Whether you're a Production Engine Remanufacturer (PER) or a Custom Engine Builder (CER), this issue has shown up in your warranty or complaint area like the nasty gremlin that it is. So let's go on a journey and see what you think.

"Low Oil Pressure" is the frightening gremlin of which I speak! Here is the situation: your customer just got his vehicle back with your newly remanufactured engine. But wait: as he returns home, as far as he can tell there is either no more - possibly less - oil pressure than the old engine had. Or, perhaps they notice that dreaded hot idle oil light flicker, even though the engine meets the minimum pressure allowed by the OE.

What does the innocent consumer believe? Defective workmanship, trying to get away with something, taking short cuts - no matter what the reality is, they feel like you're taking advantage of them!

Even though every component was machined to exacting specifications and tolerances, this problem rises up and grabs you like a mad pit bull with a death grip on your throat (see Tom Hanks in the movie "Turner and Hooch"). In more instances than I like to hear about the engine is replaced with another and everything appears to be fine.

Once the engine in question is returned, all kinds of diagnostics then take place, from oil bleed testing to complete disassembly and re-measurement of all of the components. Oil pump and pick up testing is conducted. Cam bearing oil hole locations are examined, yet invariably, nothing stands out as being a problem.

The components from that engine may be put back into the system and never see each other again as a complete unit. Yet none of the components are ever identified as a problem for any other assembly.

So how do you explain the oil pressure gremlin? More often than not you can't, and you just move on to "it happened" and that is that.

I can't give you a foolproof solution but how about one that has been extremely helpful in eliminating the oil pressure gremlins from many an engine?

Before I give you that however, let's take a quick moment to talk about what happens at the OE level when an engine is assembled. There was a time when the words "select fit" was limited to import engine applications and it allowed them to install select fit engine bearings that were slightly larger and smaller in size so that the optimum minimum bearing clearance could be obtained on each individual crankshaft journal be it connecting rod or main bearing. Well that procedure exists in nearly every engine application being assembled worldwide today.

Regardless of how stringent the procedures and quality control are on the remanufacturing side, the use of select fit bearings is neither feasible, economically sound or even available in undersize bearings.

But rising up again, as if from the dead, is the undying entrepreneurial spirit of the "engine builder." What do I mean by that? It's no trick - and for many situations they're proving to be the perfect treat: main bearings that seem to completely eliminate the low oil pressure issue.

No, they are not some voodoo magic but they are a way to address and combat the possible low oil pressure issues described above. What exactly are they? They are main bearings in which the oil grove is terminated prior to getting to the parting line.

As you'll see in Figure 1, below two different types of grooved upper main bearing shells

the oil groove terminates before it gets to the bearing parting line. This style of main bearing has accounted for a 15 percent or more increase in hot idle oil pressure. So if you're looking to eliminate some of those unexplained low oil pressure gremlins contact your bearing manufacturer and ask about this style bearing and availability for the engine applications that you are building.

you can improve thrust bearing durability, if you GROOVE the edge of the bearing in the area marked in green as it provides extra lubrication to the bearing where its needed most(the rear support face) that resists the pressure from the clutch and or/torque converter

increasing the groove, from 180 deg to 270 deg, lowers bearing support, increases oil flow rates and tends to increase wear
A special note of thanks goes out to the engineering people of ProFormance Engines, Springfield, MO, and in particular Reggie Gray.


Influence of Grooved Main Bearings on Performance
http://www.enginebuildermag.com/Article ... mance.aspx

Manufacturers are frequently asked what difference grooving makes. Various forms of main bearing grooving have been used over the years.


It’s essential to understand that bearings depend on a film of oil to keep them separated from the shaft surface. This oil film is developed by shaft rotation. As the shaft rotates it pulls oil into the loaded area of the bearing and rides up on this film much like a tire hydroplaning on wet pavement.

Grooving in a bearing acts like tread in a tire to break up the oil film. While you want your tires to grip the road, you don’t want your bearings to grip the shaft, so grooving is bad for maintaining an oil film. The primary reason for having any grooving in a main bearing is to provide oil to the connecting rods. Without rod bearings to feed, a simple oil hole would be sufficient to lubricate a main bearing.

Many early engines used full grooved bearings and some even used multiple grooves. Those choices were based on what engineers knew at the time. As engine and bearing technology developed, the negative effect of grooving was recognized and bearing grooving was removed from modern lower main bearings. The result is in a thicker film of oil for the shaft to ride on.

This provides a greater safety margin and improved bearing life. Upper main shells, which see lower loads than the lowers, and hence don’t apply the same load to the oil film, have retained a groove to supply the connecting rods with oil.

In an effort to develop the best possible main bearing designs for high performance engines, manufacturers have investigated the effects of main bearing grooving on bearing performance. The graphs (Figure 1) illustrate that a simple 180° groove in the upper main shell is still the best overall design.

While a slightly shorter groove of 140° provides a marginal gain, most of the benefit is to the upper shell, which doesn’t need improvement. On the other hand, extending the groove into the lower half, even as little as 20° at each parting line (220° in total), takes away from upper bearing performance without providing any benefit to the lower half. It’s also interesting to note that as groove length increases so does horsepower loss and peak oil film pressure, which is transmitted directly to the bearing.

Notes: You will still find some full-grooved main sets offered for older engines where demand is low and the engineering cost to bring the sets to current standards is not warranted (bearings generally represent the technology of the time the engine was developed).

here your looking at the results of an engine pulled down after only a short time running and the resulting bearing damage, its rather obvious that there was a great deal of metallic crud left in the oil passages, or oil pan, or block that got flushed into the bearings and that the block needs to be line honed and/or crank should be checked for straitness, journal taper and surface finish and roundness as the wear seems to indicate both particulates in the oil and un-even wear on the bearing surfaces
I generally see this when someone failed to pull the oil passage plugs and use a high pressure washer and solvent to clean out the blocks internally and externally after a lifter or cam or bearing fails , and remember machine shops are NOT fool proof , they are supposed to clean blocks after machine work but occasionally fail to do it correctly

READ LINKS AND ALL SUB LINKS
http://garage.grumpysperformance.co...tion-of-crank-durring-short-blk-assembly.852/

https://www.motor.com/magazinepdfs/082010_09.pdf

http://www.atraonline.com/gears/2005/2005-01/2005_01_064.pdf

http://www.4secondsflat.com/Thrust_bearing_failures.html
Crankshaft Thrust Bearing Failure - Causes & Remedies
For years both transmission and engine rebuilders have struggled at times to determine the cause of crankshaft thrust bearing failures. In most instances, all of the facts concerning the situation are not revealed at the onset of the failure. This has led to each party blaming the other for the failure based only on hearsay or what some "expert" has termed the "cause". Some of those explanations have led to an argument, that ends up in litigation while the truth lingers uncovered in the background. This document is a group effort of combined information compiled by the Automotive Transmission Rebuilders Association (ATRA), the Automotive Engine Rebuilders Association (AERA), the Production Engine Rebuliders Association (PERA), the Automotive Service Association (ASA) and bearing manufacturers. This group of industry experts has assembled the following information to consider and offers solutions that may prevent a similar thrust bearing failure.

Background:
Although thrust bearings run on a thin film of oil, just like radial journal (connecting rod and main) bearings, they cannot support nearly as much load. While radial bearings can carry loads measured in thousandsof pounds per square inch of projected bearing area, thrust bearings can only support loads of a few hundred pounds per square inch. Radial journal bearings develop their higher load capacity from the way the curved surfaces of the bearing and journal meet to form a wedge. Shaft rotation pulls oil into this wedge shaped area of the clearance space to create an oil film which actually supports the shaft. Thrust bearings typically consist of two flat mating surfaces with no natural wedge shape in the clearance space to promote the formation of an oil film to supportthe load.

Conventional thrust bearings are made by incorporating flanges, at the ends of a radial journal bearing. This provides ease in assembly and has been used successfully for many years. Either teardrop or through grooves on the flange, face andwedge shaped ramps at each parting line allow oil to enter between the shaft and bearing surfaces. However, the surface of the shaft, as well as the vast majority of bearing surfaces, are flat. This flatness makes it more difficult to create and maintain an oil film. As an example; if two gauge blocks have a thin film of oil on them, and are pressed together with a twisting action, the blocks will stick together. This is similar to what happens when a thrust load is applied to the end of a crankshaft and oil squeezes out from between the shaft and bearing surfaces. If that load is excessive, the oil film collapses and the surfaces want to stick together resulting in a wiping action and bearing failure. For this reason, many heavy-duty diesel engines use separate thrust washers with a contoured face to enable them to support higher thrust loads. These thrust washers either have multiple tapered ramps and relatively small flat pads, or they have curved surfaces that follow a sine-wave contour around their circumference.

Recent developments:

In the past few years some new automotive engine designs include the use of contoured thrust bearings to enable them to carry higher thrust loads imposed by some of the newer automatic transmissions. Because it’s not practical to incorporate contoured faces on one piece flanged thrust bearings, these new engine designs use either separate thrust washers or a flanged bearing whichis a three piece assembly.

Cause of failure:

Aside from the obvious causes, such as dirt contamination and misassembly, there are only three common factors which generally cause thrust bearing failures. They are:

• • Poor crankshaft surface finish
  • Misalignment
  • Overloading

Surface finish:

Crankshaft thrust faces are difficult to grind because they are done using the side of the grinding wheel. Grinding marks left on the crankshaft face produce a visual swirl or sunburst pattern with scratches - sometimes crisscrossing - one another in a cross-hatch pattern similar to hone marks on a cylinder wall. If these grinding marks are not completely removed by polishing, they will remove the oil film from the surface of the thrust bearing much like multiple windshield wiper blades. A properly finished crankshaft thrust face should only have very fine polishing marks that go around the thrust surface in a circumferential pattern.

Alignment:

The grinding wheel side face must be dressed periodically to provide a clean, sharp cutting surface. A grinding wheel that does not cut cleanly may create hot spots on the work piece leading to a wavy, out-of-flat surface. The side of the wheel must also be dressed at exactly 90° to its outside diameter, to produce a thrust face that is square to the axis of the main bearing journal. The crankshaft grinding wheel must be fed into the thrust face very slowly and also allowed to "spark out" completely. The machinist should be very careful to only remove minimal stock for a "clean-up" of the crankshaft surface.

In most instances a remanufactured crankshaft does not require grinding of the thrust face(s), so the grinding wheel will not even contact them. Oversize thrust bearings do exist. Some main bearing sets are supplied only with an additional thickness thrust bearing. In most of those instances, additional stock removal from the crankshaft thrust face surface may be required. Crankshaft end float should be calculated and determined before grinding additional material from the thrust face.

Crankshaft grinding wheels are not specifically designed for use of the wheel side for metal removal. Grinding crankshaft thrust faces requires detailed attention during the procedure and repeated wheel dressings may be required. Maintaining sufficient coolant between the grinding wheel and thrust surface must be attained to prevent stone loading and "burn" spots on the thrust surface. All thrust surface grinding should end in a complete "spark out" before the grinding wheel is moved away from the area being ground. Following the above procedures with care should also maintain a thrust surface that is 90° to the crankshaft centerline.

When assembling thrust bearings:

1. 
   
   • Tighten main cap bolts to approximately 10 to 15 ft.lb. to seat bearings, then loosen.
   • Tap main cap toward rear of engine with a soft faced hammer.
   • Tighten main cap bolts, finger tight.
   • Using a bar, force the crankshaft as far forward in the block as possible to align the bearing rear thrust faces.
   • While holding shaft in forward position, tighten main cap bolts to 10 to 15 ft.lbs.
   • Complete tightening main cap bolts to specifications in 2 or 3 equal steps.

The above procedure should align the bearing thrust faces with the crankshaft to maximize the amount of bearing area in contact for load carrying.

Loading:

A number of factors may contribute to wear and overloading of a thrust bearing, such as:

1. Poor crankshaft surface finish.

2. Poor crankshaft surface geometry.

3. External overloading due to.

a) Excessive Torque converter pressure.

b) Improper throw out bearing adjustment.

c) Riding the clutch pedal.

d) Excessive rearward crankshaft load pressure due to a malfunctioning front mounted accessory drive.

Note: There are other, commonly-thought issues such as torque converter ballooning, the wrong flexplate bolts, the wrong torque converter, the pump gears being installed backward or the torque converter not installed completely. Although all of these problems will cause undo force on the crankshaft thrust surface, it will also cause the same undo force on the pump gears since all of these problems result in the pump gear pressing on the crankshaft via the torque converter. The result is serious pump damage, in a very short period of time (within minutes or hours).

Diagnosing the problem:

By the time a thrust bearing failure becomes evident, the partshave usually been so severely damaged that there is little if any evidence of the cause. The bearing is generally worn into the steel backing which has severely worn the crankshaft thrust face as well. So how do you tell what happened? Start by looking for the most obvious internal sources.

Engine related problems:

• 
  
  • Is there evidence of distress anywhere else in the engine that would indicate a lubrication problem or foreign particle contamination?
  • Were the correct bearing shells installed, and were they installed correctly?
  • If the thrust bearing is in an end position, was the adjacent oil seal correctly installed? An incorrectly installed rope seal can cause sufficient heat to disrupt bearing lubrication.
  • Examine the front thrust face on the crankshaft for surface finish and geometry. This may give an indication of the original quality of the failed face.

Once you are satisfied that all potential internal sources have been eliminated, ask about potential external sources of either over loading or misalignment.

Transmission related problems:

• 
  
  • Did the engine have a prior thrust bearing failure?
  • What external parts were replaced?
  • Were there any performance modifications made to the transmission?
  • Was an additional cooler for the transmission installed?
  • Was the correct flexplate used? At installation there should be a minimum of 1/16" (1/8" preferred, 3/16" maximum) clearance between the flex plate and converter to allow for converter expansion.
  • Was the transmission property aligned to the engine?
  • Were all dowel pins in place?
  • Was the transmission-to-cooler pressure checked and found to be excessive? If the return line has very low pressure compared to the transmission-to-cooler pressure line, check for a restricted cooler or cooler lines.
  • If a manual transmission was installed, was the throw out bearing properly adjusted?
  • What condition was the throw out bearing in? A properly adjusted throw out bearing that is worn or overheated may indicate the operator was "Riding The Clutch".

How does the torque converter exert force on the crankshaft?

There are many theories on this subject, ranging from converter ballooning to spline lock. Most of these theories have little real bases and rely little on fact. The force on the crankshaft from the torque converter is simple. It is the same principle as a servo piston or any other hydraulic component: Pressure, multiplied by area, equals force. The pressure part is easy; it’s simply the internal torque converter pressure. The area is a little trickier. The area that is part of this equation is the difference between the area of the front half of the converter and the rear half. The oil pressure does exert a force that tries to expand the converter like a balloon (which is why converter ballooning is probably often blamed), however, it is the fact that the front of the converter has more surface area than the rear (the converter neck is open) that causes the forward force on the crankshaft. This difference in area is equal to the area consumed by the inside of the converter neck. The most common scenario is the THM 400 used behind a big-block Chevy. General Motors claims that this engine is designed to sustain a force of 210 pounds on the crank shaft. The inside diameter of the converter hub can vary from 1.5 inches up to 1.64 inches. The area of the inside of the hub can then vary from 1.77 square inches to 2.11 inches. 210 pound of force, divided by these two figures offers an internal torque converter pressure of 119 psi to 100 psi, respectively. That is to say, that depending on the inside diameter of the hub, it takes between 100 to 119 psi of internal converter pressure to achieve a forward thrust of 210 pounds. The best place to measure this pressure is the out-going cooler line at the transmission because it is the closest point to the internal converter pressure available. The pressure gauge must be "teed" in so as to allow the cooler circuit to flow. Normal cooler line pressure will range from 50 psi to 80 psi , under a load in drive.

Causes for excessive torque converter pressure:

There are two main causes for excessive torque converter pressure: restrictions in the cooler circuit and modifications or malfunctions that result in high line pressure. One step for combating restrictions in the cooler circuit is to run larger cooler lines. Another, is to install any additional cooler in parallel as opposed to in series. This will increase cooler flow considerably. An additional benefit to running the cooler in parallel is that it reduces the risk of over cooling the oil in the winter time—especially in areas where it snows. The in-parallel cooler may freeze up under very cold conditions, however, the cooler tank in the radiator will still flow freely. Modifications that can result in higher than normal converter pressure include using an overly-heavy pressure regulator spring, or excessive cross-drilling into the cooler charge circuit. Control problems such as a missing vacuum line or stuck modulator valve can also cause high pressure.

What will help thrust bearings survive? When a problem application is encountered, every effort should be made to find the cause of distress and correctit before completing repairs, or you risk a repeat failure.

A simple modification to the upper thrust bearing may be beneficial in some engines. Install the upper thrust bearing in the block to determine which thrust face is toward the rear of the engine. Using a small, fine tooth, flat file, increase the amount of chamfer to approximately .040" (1 mm) on the inside diameter edge of the bearing parting line. Carefully file at the centrally located oil groove and stroke the file at an angle toward the rear thrust face only, as shown in the illustration below. It is very important not to contact the bearing surface with the end of the file. The resulting enlarged ID chamfer will allow pressurized engine oil from the pre-existing groove to reach the loaded thrust face. This additional source of oiling will reach the loaded thrust face without passing through the bearing clearance first (direct oiling). Since there may be a load against the rear thrust face, oil flow should be restricted by that load and there should not be a noticeable loss of oil pressure. This modification is not a guaranteed "cure-all". However, the modification should help if all other conditions, such as surface finish, alignment, cleanliness and loading are within required limits.

Other External Problems. Aside from the items already mentioned, there is another external problem that should be considered. Inadequate electrical grounds have been known to exacerbate thrust surface wear. Excessive current in the vehicle drive train can damage the thrust surface. It affects the thrust bearing as though the thrust surface on the crankshaft is not finished properly finished (too rough). Excessive voltage in the drive train can be checked very easily. With the negative lead of a DVOM connected to the negative post of the vehicle battery and the positive lead on the transmission, there should be no more than .01 volts registering on the meter while the starter is turning over the engine. For an accurate test, the starter must operate for a minimum of four seconds without the engine starting. It is suggested to disable the ignition system before attempting this test. If the voltage reading observed is found to be excessive, add and/or replace negative ground straps from the engine to the vehicle frame and transmission to frame until the observed voltage is .01 volts or less. Note: Some systems may show a reading of .03volts momentarily but yet not exhibit a problem. For added assurance, it is a good idea to enhance the drive train grounding with larger battery cables or additional ground straps.

A special thank you goes out to Dennis Madden of ATRA, Dave Hagen of AERA, Ed Anderson of ASA, Roy Berndt of PERA and John Havel of AE Clevite for their contributions to this article.

The AERA Technical Committee

March 1998 - TB 1465R