bearing install tips


Staff member
(1) keep bearings CLEAN and verify clearances

(2)grooved CRANK bearings are usually used, installed in the the block saddles, so they are in the block, and NOT THE BLOCKS MAIN CAPS, and the oil feed holes must line up or the bearings need to be replaced or customized

(3) use of a decent MOLY BASE assembly lube prevents some problems

(4) if something binds or shows any significant resistance to rotation STOP!
verify clearances before you proceed

the looser bearing clearance has the advantage of allowing higher oil flow rates that can potentially cool the bearings faster but that higher flow requires more oil control, so a 7-8 quart baffled oil pan, windage tray etc. are a good idea



viewtopic.php?f=53&t=2726 ... ce_basics/





viewtopic.php?f=50&t=11026&p=48766#p48766 ... index.html

viewtopic.php?f=53&t=2727 ... index.html ... ewall.html




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Staff member
With all the several pre-assembly checks and then the final assembly, do you find this can be done with ONE set of bearings? I'm wondering if I need two sets, one for pre-assembly clearance checking and another set for final assembly.

How do you approach this aspect on engine assembly???



Staff member
Ive found that if you keep the bearing surfaces clean and well coated with assembly lube bearing wear during the pre-assembly checks is minimal if at all.
remember the crank journals should be polished, so they don,t really provide a wear surface when supported by the film of assembly lube, the crance cams moly cam lube paste mixed about 50%/50% with engine oil makes a good assembly lube
obviously youll at times clean off and check the bearing surfaces but the moly assembly lube tends to be a very effective protection from scuff type wear ... l=2&prt=15


Part Number: 99004-1 BACK TO LIST
Type Assembly Lube (Paste)
Size 1-Pound Container








Staff member
Since I'm not working in a Clean Room with great filtration, I was concerned about some particles getting into the lube and creating a scratch in bearing as it gets dragged thru with the crank rotation. Having an open engine, no pan, and its bottom end facing up, it just seems like the opportunity for dirt to get into the mix would be fairly high. If you have ever done any painting, you quickly find out how much stuff if floating in the air.

Just wondering what to expect, I certainly can buy more bearings when needed if I get some dirt in the assembly.


Staff member
while you have a valid point in some conditions, you naturally take the time and effort to use clean components and tools during assembly and try to work in a reasonably dry and well lighted location with the engine up on an engine stand,and frequent use of lint free wipes, soaked in marvel mystery oil helps, as it keeps the metal surfaces from rusting or collecting crud, Ive generally found that if your cover the engine with a large plastic bag and duct tape, when your not actually working on it, its not been a factor worth worrying much about, in a reasonably clean shop with no open doors to let in wind carried debris.
heres some pictures I found on the web that may help



if you find the rotating assembly is more difficult to rotate than you expected, you may want to verify some clearance issues that get over looked at times,
theres also some, other potential issues,
theres a slight potential for the piston wrist pins too not rotate effortlessly in the piston pin bores ,

that may add to the difficulty in rotating the assembly in the block.
the piston rings must have vertical and back clearance in the piston ring grooves




Piston Ring Groove Clearance
Pistons are grooved to fit rings that seal the cylinder’s compression and allow for lubrication of the cylinder walls. Piston rings come in a set. There are two compression rings. The top ring is affected by the most cylinder compression pressures. The second compression ring reinforces the top ring. The third ring down is the oil ring. It controls lubrication between the piston and cylinder bore.


Place the new ring into the top piston groove, and then place a feeler gauge into the gap between the new ring and the upper land. Move around the pistons groove and obtain a few measurements. Compare this reading to specifications. If this reading is too much and the gap is too large, the piston must be replaced. The top ring takes the most compression. This causes the ring to slap against and wear the lands in the piston groove.



and of course the pistons must have the correct piston too bore clearance. and connecting rod can only be installed facing one direction







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BTW when you go to buy a ring compressor....this type(ABOVE & BELOW) works far better than the others, but its specific to a very limited range in bore size applications


Proform 66766 $31

remember to dip the piston and rings in high quality oil just prior too or before assembly I,ve used MARVEL MYSTERY OIL FOR DECADES



this style ring compressor below has a nasty habit of not keeping the rings evenly compressed and not seating evenly on the block , Ive used them but the type above is much easier to use





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


Clevite H-Series main bearings were developed primarily for NASCAR racing, but are well suited to other types of competition engines as well. They're especially good for engines that run at medium-to-high revs. They have steel backings with carefully selected overlays and a high crush factor, plus a medium level of eccentricity. H-Series bearings have enlarged chamfers at the sides for greater crank-fillet clearance and are made without flash plating for better seating. They're also available with either 180 degree or 360 degree oil grooves, as well as an extra 0.001 in. of clearance. the 180 degree groove bearing with only the top 1/2 groove in the block is preferred as having the lower 1/2 in the main cap without the groove, has a higher load capacity



LOOK CLOSELY the upper main bearing, that seats in the block, is grooved the lower half that seats in the main cap is NOT GROOVED
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Staff member
That answers my question....thanks! With reasonable care and a heavy plastic bag it should not be a problem, and if it is, I can always replace a single bearing.


Staff member ... o_bad.aspx

CSI: Engine Bearings: When Good Bearings Go Bad

There can be literally dozens of reasons for premature wear or failure of an engine bearing. Luckily, the criminal always leaves a trail.

By Doug Kaufman

Doug Kaufman

Engine bearings have the dual function of reducing friction between a rotating part of the engine (the crankshaft) and the stationary part (the main caps and engine block) and supporting the crank.

Because of the stresses caused by the explosions inside the internal combustion engine, the bearing material must be extremely strong, so a durable metal is required.

Reducing friction is accomplished in part by the fact that dissimilar metals slide against each other with less friction and wear than similar materials will. So an alloy bearing material does a much better job of keeping a steel crankshaft moving than a steel or cast iron bearing will.

Although the material itself may give the engine bearing some friction reducing properties, its performance is enhanced by a lubricant between the moving and stationary surfaces. Another of the bearing’s duties is to establish and maintain a film of oil.

For all these requirements, the bearings usually do a very good job at keeping the moving parts moving. However, when a bearing fails the results can be spectacular – and catastrophic.

But even when they fail, the fault usually doesn’t lie directly with the bearing itself. There is usually another, less obvious culprit behind the crime, which may force engine builders to employ some CSI-like investigatory tactics.

There can be literally dozens of reasons for premature wear or failure of an engine bearing. Luckily, the criminal always leaves a trail. By carefully inspecting the evidence left behind, an engine builder can discover and eliminate the cause of bearing failure.

Some failures will be caused by a combination of factors, but the photos that accompany this article (additional pictures can be found online at can help you determine the most likely cause of failure.

Dirt or Debris
Whether it’s dirt, dust, grinding remnants, shot or any other particle, debris can cause significant damage to a bearing surface.

If it’s in the lubrication system, dirt will usually leave circumferential scratches and often the offending piece will remain lodged in the bearing’s surface. Always be sure the lubrication system is flushed thoroughly before reassembling an engine.

Another way dirt can play havoc is if the engine components aren’t completely clean. A foreign particle trapped between the bearing back and the housing will cause a raised area in the bearing. This little hump can lead to contact between the bearing and the crank journal. You should always ensure the bearings are installed in clean surfaces.

Insufficient Lubrication
A complete lack of lubrication in the crankcase usually leads to seizure of the bearing and total failure of the engine. But experts say a more frequent issue regarding lubrication is simply inadequate oiling.

The absence of a proper oil film will result in metal-to-metal contact, occasionally to just one bearing or often to a number of them.

When the bearing is damaged by oil starvation you’ll find a very shiny surface and evidence of wiping.
Remember, the failure of the oil film can be seen in a variety of ways on the bearings. Check or such things as blocked oil passages, a malfunctioning oil pump, improper bearing selection or installation, oil seal failures, fuel dilution (often caused by blowby of fuel and air past the piston rings) or foaming or aeration, caused, ironically, by an overfilled crankshaft.

Sometimes, failures are the result of simple installation errors. For example, if a bearing half without an oil hole is improperly put into a position where the hole is needed, that journal will receive no lubrication.

Other types of assembly errors may also be seen. If a connecting rod or main bearing cap is installed in the wrong position, or a bearing isn’t set into place securely, lubrication will be insufficient and cause failure.

Careful installation procedures are, of course, critical in every aspect of engine building – careless errors are always expensive.

Machining Issues
As with the installation issues, problems in the machining process can often result in bearing failures.
An out-of-round housing bore will cause the bearing to eventually conform to the out-of-roundness. This can decrease the oil clearance enough to cause metal-to- metal contact, resulting in areas of heavy wear. Engine vibration or alternating loading and flexing of the connecting rod can be the cause.

Another cause of bearing failure can be seen in a crankshaft that has been refurbished with a grinding wheel in poor condition. Hourglass-shaped, barrel-shaped or tapered crank journals will result in uneven or improper lubrication. Load distribution across the bearing will also be uneven, and the bearing will show uneven areas of wear.

Fillet ride occurs if the radius of the fillet in the corner of each crank journal is larger than needed. The edges of the bearing can then ride on those fillets rather than fitting neatly between them. This metal-to-metal wear will cause excessive wear and bearing failure.

When grinding the crankshaft, be careful to use a grinding wheel in excellent condition to maintain the necessary geometry of the fillet radii.

There are a number of reasons that the crankshaft and block housings may be misaligned, including improper machining, a bent crankshaft or damaged engine block. Each of these problems will likely cause significant damage to some of the bearings and less to others. Your investigations will focus on the tolerances to ensure the block and parts are within manufacturer specs.

Rebuilders should also always carefully inspect connecting rods to make sure they are not twisted, as this can cause uneven bearing loading and wear.

The term “crush” refers to the outward force created by the portion of the bearing, which extends above the housing bore when the bearing halves are set into place. This “extra” material holds the outside diameter of the bearings firmly against the housing bore when the assembly is torqued to specification. By increasing the surface contact between the bearing and connecting rod housing bore, crush minimizes bearing movement, helps to compensate for bore distortion and aids in heat transfer.

In simple terms, bearing crush is what holds the bearing in place. Think of it as putting 10 pounds of something into a 5 pound bag. The tang or locator tab on the shell that fits the saddle is only for locating the bearing during assembly.

When crush is correct, slightly elliptical bearing shells conform to a perfect circle when they’re torqued into place. In this way, the crankshaft rotates properly.

However, when there is excessive crush, the additional compressive force causes the bearing to bulge inward at the parting lines causing side pinch.

Excessive crush may be the result of an attempt to reduce oil consumption by filing down the bearing cap, assembling the bearing caps too tightly by over torquing the fasteners or, in some cases, using too few shims.
Insufficient crush, on the other hand, will result in bearings that are not held securely in the bore, and remain free to move back and forth within the housing. Because contact between the bearing back and housing bore is necessary for cooling, this condition means heat transfer away from the bearing is impeded, resulting in overheating and deterioration of the bearing surface.

Insufficient crush may be caused by the improper attempt to achieve a better fit by filing the parting faces, by dirt or burrs holding the bearing caps open, improperly torquing the fasteners during installation, improperly sizing the housing bore or (if needed) using too many shims in the assembly process.

Shiny areas will be seen on the back of the bearing due to its rubbing back and forth. In some cases, discoloration may be seen where oil has worked its way between the two surfaces and burned.

Overloading may be caused by vehicle operator error. Excessive idling can result in an oil film that can’t support the load needed.

Engine lugging can distort either (or both) the crankcase or crankshaft, affecting either (or both) the connecting rod and/or main bearings.

Hot rodding, or forcing excessive loads, can similarly affect the bearings. Engine tuning and operating conditions should always be followed and appropriate bearing materials chosen for the application.

A vehicle that leaks oil, causing oil starvation, has its share of issues, as we have seen, of course. But some vehicle owners who have cars or trucks that do not leak oil are in an even more potentially serious situation. At least the leaker lets you know it needs oil added now and then, with fresh oil maintaining its levels. The engine that seems to be leak free can be overlooked, yet after a certain amount of time, the oil begins to degrade. The acids in the oil then attack the bearing surface.

Proper selection of bearings will go a long way toward a successful engine build. And checking assembled bearing clearances to make sure the bearings are not too tight or too loose should always be done as a final check to make sure oil clearances are within the desired range for the engine.

Attention to the machining and material selection processes at the front end should help reduce the chance of bearing failure down the road. But armed with these forensic tools, should those mysterious bearing failures occur, you should easily be able to solve the crime.


metallic machining trash, left in engine

Overplated copper alloy bearing gouged by cast iron debris.(wiped cam) Inset photo shows the microscopic detail of the gouges

The reasons bearings fail are many and varied, but they’re not usually the fault of the bearings themselves.

This aluminum bearing was damaged by embedment of glass beads. Inset photo shows the extent of the damage.

Foreign particles in the bearing lining may be the result of improper cleaning or a failure to replace the filter and may include road dirt and sand

Lubrication is vital. This shows the result of a dry start. The bearings on the left, furthest from the oil pump have the most wear.

Low oil supply or oil starvation doesn’t just sound bad, it does bad things inside the engine.

Too rich a mixture or blow-by past the piston ring can lead to dilution of the oil.This damage can be seen here

Excessive wear seen near parting lines of upper and lower shells was caused by Bearing Cap Shift. This results in metal-to-metal contact and excessive pressure-causing deterioration.

Fillet ride occurs if the radius of the fillet in the corner of each crank journal is larger than needed. The edges of the bearing can then ride on those fillets rather than fitting neatly between them.

Distress from excessive idling results in an unsupportive oil film.

These upper connecting rod bearings show distress caused by lugging. The lower main bearings were similarly affected.

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








Staff member
during any engine assembly process youll want to keep the block and any rotating assembly components and valve train parts absolutely clean, and lightly oiled to prevent rust, but the oil can trap dust and dirt if you don,t work in a clean and reasonably dry and well ventilated area with decent lighting. a large plastic bag makes a good temporary dust barrier when your not actually working on the engine.

23301a.jpg ... 60669.html





while your doing the clearance work and pre-assembly checks you-ll want to use a good many lint free ,oil soaked rags for cleaning and oiling surfaces, but during the final assembly process a generous slathering of MOLY assembly lube mixed with about 15% light machine oil to form a loose honey-like consistency that can be brushed onto crank and rod bearings and all the valve train components before assembly helps prevent wear issues, but youll want a ONE TIME USE
Paint Brush , with Nylon Bristles 1 Inch Wide Brush, because natural bristles tend to shed ,bristles, absorb moisture and contaminate the assembly lube
coat the bearing surfaces in the block, lay the crank in place and brush assembly lube on the main bearing journals then before installing the main caps spin the crank by hand and pay attention if it tends to drag, or bind, then coat the bearings in the main caps and install and torque them to spec. the crank alone should easily spin with less than 10 ft lbs required, as you add each piston and rod assembly dip the whole piston and ring assembly in clean motor oil and make sure the rod bearings and rod journals are coated with assembly lube.

ID suggest you read these links ... fters.aspx













read this

Molybdenum Disulfide (Moly) has been used for decades in lubricating pastes and greases because it is slippery and forms a protective coating on metal parts:

Single Molecule of MolyMoly exists as microscopic hexagonal crystal platelets Several molecules make up one of these platelets. A single molecule of Moly contains two sulfur atoms and one molybdenum atom. Moly platelets are attracted to metal surfaces. This attraction and the force of moving engine parts rubbing across one another provide the necessary thermochemical reaction necessary for Moly to form an overlapping protective coating like armor on all of your engine parts. This protective armor coating has a number of properties that are very beneficial for your engine.

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.

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.
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 ... reakin.pdf

spraying the cam surface with moly and then coating it with moly assembly lube before installation tends to help.
S00200.jpg ... paignId=WZ


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

viewtopic.php?f=54&t=615&hilit=+mobile+filter ... 1578676008 ... index.html



viewtopic.php?f=62&t=1515 ... CEDURE.pdf ... index.html


ctrp_0807_03_z+flat_tappet_camshaft+engine_lubricants.jpg ... index.html

the assembly lube, oil and clearances are critical to durability


you might want to read thru this

preventing cam & lifter break-in failures

viewtopic.php?f=62&t=1515 ... CEDURE.pdf


it should be rather obvious that theres options, cam failures are usually the result of incorrect CLEARANCES or too much SPRING PRESSURE or LACK of ADEQUATE LUBRICATION,USE DECENT MOLY CAM LUBE, and decent quality oil, adding MAGNETS to trap metallic CRUD HELPS, be sure to change your oil filter and oil after the first 3-4 hours or 100 miles as theres bound to be crud and assembly lube trapped in the oil and filter

the old familiar stuffs Part #1052367 is getting hard to find
E.O.S. was discontinued but.....
the new stuff...
(use the drop down menu)
Part 10-106
E.O.S. Assembly Lubricant (1 pint)

its still available if you know where to look, most but not all parts counter guys will know this but youll run into a few who just insist its not available



btw MOLY base lubes are your first and best break-in lube during the first few minutes

CRANES Super Lube Break-In Concentrate is an anti-wear additive formulated with a high concentration of special zinc dithiophosphate to provide sustained protection against cam lobe and lifter scuffing and wear. This oil supplement is to be added to the engine oil for the initial break-in period after the installation of a new camshaft and lifters.
Now it should be obvious that reducing the pressure at the contact point between the lifter and the cam lobe will tend to reduce the tendency for lifter & lobe wear, and increasing the coolant flow at that point helps, so its generally a good idea to remove the INNER spring on DUAL spring valve trains during the break -in process, to reduce pressures while the parts lap in, and a few minutes with some 1000grit sand paper to remove burrs from the lifter edge sure helps in most cases

Part No. 99003-1 -- 8-ounce container

a decent BILLET cam core and quality roller lifters will prevent a great deal of cam lobe wear issues


when you say 215F do you mean the normal rise in temp after shut-down?

oil temps SHOULD reach 215F occasionally during engine operation,
to insure all moisture is boiled off
but keep in mind , oil in the sump is going to be significantly cooler than,
oil flowing over,
rocker pivot balls,
cam lobes,
valve springs lifters,
piston skirts and rings
oil, flowing over the moving and sliding components absorbs a great deal of heat,
that hot oil flowing over the engine block and heads has,
its heat load rapidly absorbed and transferred too coolant,
flowing through the major components, that coolant absorbs heat from the hot oil,
and transfers it to the outside air flow ,
and air flowing over the oil pan and valve covers is easily 40F-100F cooler than the oil,
this is how much of the initial heat is transferred,now oil in your oil pan will be by design cooler than it is in other locations,
and oil flow cycles endlessly so while your engine may only hold 4-8 quarts, theres 2-7 gallons a minute passing through the oil pump,
that flow changes, depending on clearances and rpms of course, so the longer any engine runs the more passes,
the individual oil molecules have of being repeatedly heated and cooled, thus moisture boiled out, but moisture will not be totally removed unless,
oil reaches about 215F repeatedly,

this almost mandates a 190F-205F oil pan oil temp.





as a general rule you select .001 bearing clearance for every inch of bearing journal diameter,
Rod bearings 0.002 - 0.025" , side clearance 0.010 - 0.020"

Main bearings 0.002 - 0.003" for most engines ( 0.020-0.025 bearing clearance on small blocks, .025-.027 bearing clearance is about ideal, on big blocks ), 0.005 - 0.007 crankshaft end play
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