# Sticky  Main Bearing Check



## PontiacJim (Dec 29, 2012)

Just had to pass this along as one of the PY members has had a bad experience when his freshly rebuilt engine got its first road test and locked up.

The member was pretty upset and was ready to sell the car because he was at wit's end in putting money into it and didn't want to throw anymore at it. After he calmed down, he pulled the engine and opened it up for inspection.

Keep in mind that the engine was assembled by the owner while the machine shop did all the machining work and he purchased a stroker kit from Butler.

The armchair engine gurus all had their theories as to what happened. However, what was found was that the aftermarket crankshaft used a large fillet/radii where the crank weights roll into the crank journal - the corners. Enclosed a photo and the fillet/radii is what the guy's finger is pointing to.

A large fillet/radii is what you want as it makes the crank stronger. But, the owner wanted to assemble his own engine as many of us do. He did all the usual checks for tolerances and measurements that were needed and that he knew to do. The lack of engine assembly experience and not knowing to check the fit of the bearing to the crank at the fillet caused the #5 main bearing to lock up on the crank fillet.

This is not anything new to check, but it is something many don't know to check or miss. With a large fillet/radii on the crank journal, a bearing with a matching chamfer needs to be used. Some will even use a slightly narrowed down bearing, either purchased as such or machined by a machine shop. I know to check for this from all my reading. But I find it interesting to read all the PY guff as to who is at fault and who gets to wear the blame on this - ultimately it is the owner who assembled his own engine because it is up to him to check all tolerances and clearances and this one escaped him with bad results that could have been worse.

I put together a montage of replies and suggestions pulled of the PY forum and the blame goes on the crank, the bearings, and they even rank on Butler for their explanation of the event. But, in all this, I have to ask why Butler was not aware of this situation when the stroker kit comes with bearings that should have worked with the crank supplied. So Butler might be another angle that can be tossed into the blame mix, but in my opinion, it is ultimately the owner who assembled his own engine and learned a hard lesson - as I too have done in many instances. Take it on the chin and accept responsibility and move forward. Just another example in my book where the blame is passed around on anyone but the guy who assembled his own engine - ie, owner error on this one.

*Butler's Reply on the Matter*
From Butler:
-- "We have seen this with every brand of bearing and it seems to be more a difference in the blocks to us (most likely core shift over time possibly?)
--We just recently had the same issue with a 389 but this is something we always check and sometimes have to slightly narrow and/or re-chamfer the bearing.
--This is just part of the blueprinting process and a step we always check."

PY Member - You can use an old fashioned bearing scraper or a file or even a sharp knife and dress down the side of the bearing to clear the fillet on the crank. I just did this last year when assembling my engine. The machinist showed me the trick when he sold me the bearings......it takes a little time,

*Member's Synopsis*
--When you measured your thrust end-play, the crank was stopping short of reaching the rear-facing thrust face on #4 and instead stopping because the crank journal radius was hitting the rear edge of the #5 bearing shell. The #5 bearing edge and crank journal radius was under extreme contact from the pressure plate pushing the crank forward when shifting the trans until the engine locked up.


*Crank Blame*
--My machinist said that with aftermarket crankshafts, specifically my Scat and an Eagle he measured, they are longer compared to the stock Pontiacs he measured. Either overall or in a specific area, I don't know, he has some stock Pontiac cranks, Scat 400/455 cranks, and an Eagle crank he measured and the after market cranks (including mine) are 0.005-0.006 thousandth longer and therefore my endplay is fine, but rubbing up against the #5 bearing, not the thrust bearing. If I had tested end play with a stock crank, it would have been too tight.
-- So, when one measures end play, you get a good measurement. This is a false measurement though. Had I used a stock crank, I would have had too little endplay with these bearings and known there was a problem. (Note from PJ: Hmmm, if the stock crank fillet/radii is actually smaller than the aftermarket fillet/radii, I don't see how you would get too little end play, and if anything, the smaller fillet/radii of the stock crank may have worked with the supplied bearings and the engine would have been fine)

*Bearing Blame*
--The issue looks like the #5 rear bearing was sitting too far back toward the radius! If the tangs are indeed 20 thou off that could have been the issue. AGAIN!, ALL other bearings were good!
--Here are pics of the Clevite and FM bearings in the block.The crank has been cut 10 which cut some of the radius.The Clevite sits a little farther back in the block.
-- Question: Would the first photo present a problem? Answer: Depending on the radius! By the look of the seized bearing the machinist thinks so. Hard to tell now that the crank has been turned. *He just think it’s another thing that needs to be checked close on all builds.* (Note from PJ: Duh? A good machine shop or engine assembler would check for this as part of their process, just as Butler stated they do. It took this engine to now begin to check for the bearing chamfer/fillet clearances?)
-- If the #5 bearing tangs are 20 thous off, compared to what? The saddle center? The crank main journal? An original GM 455 bearing? Or another aftermarket bearing? So now the blame automatically, and quickly, falls on Clevite as being a bad bearing choice because they have poor quality control and they use off shore manufacturing. Federal Mogul is now the choice of champions according to the engine gurus - stay away from those evil Clevites.


*Thrust Bearing Installation: Take Your Time*

This is done AFTER you have checked your main bearing clearances dry using the plasti-gauge method that most of us use. 

After checking your bearing clearances dry, remove the crank and be sure to thoroughly lubricate the exposed main bearing and thrust bearing surfaces with a quality engine assembly lubricant or, at the very least, a clean 30-weight non-detergent engine oil. Then drop the crankshaft back into place.

Instead of simply installing the main bearings and thrust bearing and tightening the main cap fasteners to the factory-specified torque value, spend a few extra minutes in an effort to maximize thrust bearing life.

One method of setting up a new set of bearings is to check the endplay without the main caps installed. You can also visually see if there is any interference or contact between the edge of the main bearing and the crankshft fillet/radii - you should see space between them.

First install all main bearings and caps into position, tap them with a rubber/plastic mallet to seat the main caps, then tighten the main cap bolts (or nuts, in the case of main cap studs) to a minimal value of about 10 to 15 ft.-lbs., following the factory-recommended tightening sequence. This initial snugging of the fasteners will seat the bearings into their respective block and cap saddles.

Then remove all the main caps. Next, you will need a magnetic base and dial indicator. Attach the magnetic base and dial indicator to the front of the block and align the dial indicator plunger parallel to the crank snout and lightly force the crank backward towards the bellhousing end using a clean pry bar or a long flat-blade screwdriver, and then zero the dial indicator. Look at your clearances between the edge of the main bearings and fillet/radii to ensure you have some clearance between the bearing shell edge and fillet/radii on the crankshaft. Then with the dial indicator set on "0", lightly force the crank forward (water pump end) and read/record the amount of movement on the dial indicator. This will give you the clearance for the upper thrust bearing in the block. Again, look at your clearances between the edge of the main bearings and fillet/radii. You can repeat this procedure to verify your numbers.

Next re-install all main bearings caps/bearings into position, tighten the main cap bolts (or nuts, in the case of main cap studs) to a minimal value of about 10 to 15 ft.-lbs., following the factory-recommended tightening sequence.

Then, loosen all of the main cap fasteners again, but don’t disturb the main caps and using a rubber or plastic mallet, tap the crankshaft rearward to close up the front thrust clearance. Finger-tighten all main cap fasteners.

Next, use a clean pry bar, such as a long flat-blade screwdriver, to force the crankshaft fully forward. This will help to align the rear thrust bearing faces together. The rear thrust bearing face is the critical side as it is the side that takes all the pressure when the clutch is pushed in and forces the pressure plate forward which in turn pushes the crank forward against the thrust bearing.

Lightly force the crank backward (bellhousing end) again using the pry bar, or long flat-blade screwdriver, set up the dial indicator and zero the dial indicator. Now with the dial indicator set on "0", lightly force the crank forward (water pump end) and read/record the amount of movement on the dial indicator. The measurement should be the same as for the upper thrust bearing shell. However, there may be a different between the two halves and these will need to be squared up. You can also repeat this step to verify your crank movement and thrust bearing clearance.

Sometimes the upper and lower halves of a thrust bearing are slightly different in thicknesses at the thrust shoulders. As an example only (use factory specs), if you have .007" endplay with the upper insert only in the block and then .005" with the main cap and lower insert installed, there is a .002" misalignment somewhere. You can use a feeler gauge between the thrust faces and the crank to confirm the difference between the two shell halves and determine which side of the thrust bearing will need to be sanded. Then use a glass plate or known flat surface to sand the thrust face having the smaller number (.005) using a full sheet of 400 to 600 grit wet/dry sandpaper with a few drops of light machine oil like Marvel Mystery Oil to lubricate the process to match the other bearing half of .007" with the cap installed. This prevents all the thrust load of the crank shoulder from being loaded on only the upper or lower half of the thrust bearing. Use a figure-8 sanding motion to get an even sand.This may take a little time, but test fit the thrust bearing and check the clearance. Make sure you thoroughly clean and wash the bearing each time as needed before re-installing it back into the engine to re-check your progress.

Once the bearing halves are equalized, it is time for a final assembly. While holding the crankshaft in the pushed-forward position with a pry bar, once again tighten all of the main cap fasteners to 10 to 15 ft.-lbs. You may now release pressure by removing the pry bar. Finish tightening all of the main cap fasteners to their final specification, in two or three equal steps.

When all the main caps have been torqued, re-check the endplay one more time to confirm it is still that same. If not, it could indicate a problem and you will have to find the cause.

Here is a pretty good YouTube video on crank installation. It is a little lengthy and way too many ads for me, but still good.


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## 67ventwindow (Mar 3, 2020)

Thank you sir for your time and effort in this write up. This is the second article I read this weekend about the craftsmanship envolved in maintaining and bring these cars back to life. We get use to modern cookie cutter parts that is they are not exact we send them back and say the part is at fault. Some times it is, sometimes the process of creating the part has changed in the fifty years since they rolled off the assembly line. Sometimes the 50 year old pride and joy has sagged or warped. I enjoy working on my vintage vehicles. I am fortunate enough that they are not my sole source of transportation. Maybe that is why they are still a joy to me.


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## PontiacJim (Dec 29, 2012)

67ventwindow said:


> Thank you sir for your time and effort in this write up. This is the second article I read this weekend about the craftsmanship envolved in maintaining and bring these cars back to life. We get use to modern cookie cutter parts that is they are not exact we send them back and say the part is at fault. Some times it is, sometimes the process of creating the part has changed in the fifty years since they rolled off the assembly line. Sometimes the 50 year old pride and joy has sagged or warped. I enjoy working on my vintage vehicles. I am fortunate enough that they are not my sole source of transportation. Maybe that is why they are still a joy to me.


Your welcome. I, like most here, like to do my own work on my cars - that's the joy's and frustrations of ownership. I have said before that no one knows it all and I certainly don't. I learned much of what I know through printed material, talking with others, and hanging at engine machine shops, tearing down and scrapping many cars, junk yarding in my youth, and a lot of hands-on experience by sometimes digging in blindly and figuring out what I needed to do to get my car repaired so I could drive it again. Sometimes I broke perfectly good parts because I did not know the correct/proper way of doing something and then had to buy another replacement part to get it right.

I hate it when I go about doing some form of repair, fix, or assembly and I either had to fight with it, or like the guy over on PY, got into a major situation and spent a lot of hard earned dollars only to have something go wrong that IF I had only known what to look for or check, I would not have been in the pickle I have myself been found in.

For many of us there is pride in working on our cars even amid all the frustrations, curse words, and tools being thrown about. LOL It is a great feeling of accomplishment when whatever we have chosen to tackle on our cars has worked out the way we had hoped and the car is fixed and up and running again. Let's be honest, there are "bragging rights" amongst our peers who have the same interests and type cars, and at the gas stations, restaurants, and car shows where people are looking your car over and you can go into detail about the car and what you have done with it, and to it.

Knowledge about these old cars and how to repair them and keep them running is your best friend. I don't think you can ever learn enough as there is always that one more thing you pick up from somewhere that becomes information that you can use - and may save you a lot of grief. True, there are many who want to be helpful, but really don't know enough to keep you out of hot water.

Often today's vehicles with their advanced technology, better designs, better metallurgy, and better machining process seem to want to be transferred over to our older cars when they were never built or made for such specs as found on our present cars - apples and oranges, and you just have to accept it as such and pushing the envelope to get our old cars up to speed in today's world can turn out to be a disappointment or disaster. So following manufacturer's specs through things like Factory Service Books for your year car is the safer bet in many instances - you won't be apt to get into as much trouble.

Are there viable upgrade? Absolutely. Front disc brakes, dual reservoir master cylinder, electronic ignitions (if you don't have the knowledge for points which are just as good), front/rear sway bars, EFI (if you are not a carb guy) and electric fuel pumps, and LED lighting just to name a few. You can certainly make upgrades to engines and transmissions, but with these, you are not only spending a lot of $$$, you can lose some of what the original experience of these cars provide. I don't want a modern old car - I can drive my Hyundai to get that. I want lumpy idle (rich gas smell as well burning my eyes), the deep sucking drone that only a Q-jet makes when it kicks open, a throaty & loud exhaust, horsepower & torque, tires that I can smoke off the starting line, a transmission I can shift manually (manual or automatic) that will bark off some rubber when it shifts to the next gear - I want a car I drive and control, not one that drives me and all I have to to is point, steer, and hit the gas and all is quiet. It's the difference between a wild stallion and an old mare. I want the wild where I respect it for what it is and yet know how to control it and every once in a while, it controls me and I have to use my skills to get it back under control. That old mare just goes where it is told and is a boring ride in my book.

So I think many of us share the same philosophy in our car ownership - we like to work on them when it is something we can tackle or at least give it a college try. We like "bragging rights" through ownership and the work we put into them ( and not the car's resale value - those are the shallow people). We don't mind upgrading our car to improve safety and performance without destroying what the car experience offers as it did from the factory. We like a car that we have control over and drive it with authority, rather than sit in a quiet cabin, listening to the bluetooth stereo, no hint of engine lope or loud exhaust, and blend in with everyone else on the road. We like being different because we are cool, many of us old, but still cool. LOL


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## RMTZ67 (Mar 12, 2011)

One wonders how we got by in the past,😱 Or my memories fading...I dont remember degreeing a cam,breaking in a cam @2800 rpms or lint free cloths and hair nets lol.Times have changed,but got to agree with you Jim, we're still coolold but cool.


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## O52 (Jan 27, 2019)

RMTZ67 said:


> One wonders how we got by in the past,😱 Or my memories fading...I dont remember degreeing a cam,breaking in a cam @2800 rpms or lint free cloths and hair nets lol.Times have changed,but got to agree with you Jim, were still coolold but cool.


You got that right. My first engine rebuild was a 331 Chrysler Hemi that was given to me. Full of water from sitting outside, I cleaned, honed the block, and installed new rings and bearings plus a valve job that a friend did for a couple cartons of Camels. With some Plastic gauge, a cheap beam torque wrench, Motors manual, and a borrowed engine stand, I worked outside in the driveway using basic hand tools. That puppy fired right up and kicked azz in an old Desoto I had bought for $40. You always remember your first one LOL.


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## PontiacJim (Dec 29, 2012)

Yep, for some reason most seem to think our old cars require the skill of a surgeon to assemble them. I am so glad I didn't know then what I know now or I may have never gotten the nerve to pull cars apart and do the backyard mechanic stuff I did. Pulling an engine outside in the dirt with 3-pieces of pipe chained together at the top to create a tri-pod and a come-along - and the tri-pod was a borrowed item that got passed around to others when an engine got pulled - no hydraulic engine lift back then.

Re-ringed a small block Chevy in a 1970 pick-up for a friend and a few extra bucks. Left the engine in the chassis. Removed the top end, removed the pan to release the rods/pistons, honed the old worn cylinder with my NAPA bought 3-stone hone, put on new rings on the old cast pistons, and put it all back together. Ran great and I think it went another 10 years. What was I thinking? No new rod bolts, no measuring for out of round cylinders or even bore size, re-using old cast pistons, and my word, scraping off the old head gasket as best I could. LOL

It's not a Ferrari, its mass produced with tolerances that are forgiving with high and low specs. If there is a Zombie Apocalypse, or Covid-19 Apocalypse, and the world come to a stop, I'll be keeping the cars/trucks running so I can survive while others get that blank stare because they don't have a CNC machine & program, a computerized milling machine, a ball micrometer, torque plate, or hot tank - _because I am a backyard mechanic._


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## 67ventwindow (Mar 3, 2020)

While pine needles make a comfotable bed to lay on. The sap will have you looking like chewbaka when you emerge from under the car. We all knew better than to park under pine trees in FLA. For some reason we picked a pine tree to attach a block and tackle and remove the engine.


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## Old Man Taylor (May 9, 2011)

RMTZ67 said:


> One wonders how we got by in the past,😱 Or my memories fading...I dont remember degreeing a cam,breaking in a cam @2800 rpms or lint free cloths and hair nets lol.Times have changed,but got to agree with you Jim, we're still coolold but cool.


We weren't using aftermarket parts then. Also. we weren't knowledgeable enough to degree cams. That came later, but it was just important "in the old days". As to breaking them in, the oil was much better and the spring pressures were low. I know I started breaking my cams in around 1970.


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## RMTZ67 (Mar 12, 2011)

Old Man Taylor said:


> We weren't using aftermarket parts then. Also. we weren't knowledgeable enough to degree cams. That came later, but it was just important "in the old days". As to breaking them in, the oil was much better and the spring pressures were low. I know I started breaking my cams in around 1970.


How about lint free rags and a hairnet to keep a hair from falling onto your crank lol.


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## PontiacJim (Dec 29, 2012)

RMTZ67 said:


> How about lint free rags and a hairnet to keep a hair from falling onto your crank lol.


Lint free rags? What, paper towels or an old rag made from a former worn out T-shirt wasn't good enough? Hairnet? My hair didn't fall out back then, now, a different story. LOL


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## 67ventwindow (Mar 3, 2020)

RMTZ67 said:


> How about lint free rags and a hairnet to keep a hair from falling onto your crank lol.


Hairnets are not as vital when your twenty. But that was many moons ago. We had a service that took care of our rags at my family's service station and had the endless hand towel in the bathroom.


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## 1968gto421 (Mar 28, 2014)

Re: Post #1, Jim mentions armchair gurus on the PY forum which implies that folks there lack knwledge/experience to do a diagnosis on a car problem.While many members there are amateurs offering advice bsed on whatever, a large number there are pros donating their time and knowledge to help others out. To that end I submit the following link to acquaint folks with some of the guys there sharing their knowledge in an interesting read:






Just a question, So how many of the members - PY Online Forums - Bringing the Pontiac Hobby Together


Just a question, So how many of the members Pontiac - Street



forums.maxperformanceinc.com


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## RMTZ67 (Mar 12, 2011)

1968gto421 said:


> Re: Post #1, Jim mentions armchair gurus on the PY forum which implies that folks there lack knwledge/experience to do a diagnosis on a car problem.While many members there are amateurs offering advice bsed on whatever, a large number there are pros donating their time and knowledge to help others out. To that end I submit the following link to acquaint folks with some of the guys there sharing their knowledge in an interesting read:
> 
> 
> 
> ...


Interesting to say the least, I have had no reason to venture past this forum in the last 10 years since purchasing my Gto. I have been truly impressed with the quality of knowledge and interest to help here. My 67 Gto is the first Pontiac I owned and couldn't have rebuilt and produced this Gem I got without you all. The first lesson I got was firing order runs counter clockwise  Now my favorite car I have owned.


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## 67ventwindow (Mar 3, 2020)

Sorry but when years of experience, professional and experts are thrown out there. I cringe.


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## 1968gto421 (Mar 28, 2014)

67ventwindow said:


> Sorry but when years of experience, professional and experts are thrown out there. I cringe.


These guys were responding to a request from one of the "big guys", they have never in the past mentioned their credentials. I agree when someone tells me how good he is I too cringe. My point was to show that PY members don't sit in easy chairs pontificating what they found on google to solve another member's problem, the vast majority are out there working on cars and have frequently something to offer to other members like on here. I depend on both forums for help as well as lurk on the Firebird/TransAm forums for drivetrain info I have not found elsewhere. I was merely pointing out that there are other folks out there who are able to be helpful and have some actual knowledge from their own experience. Besides menbers here I have also had some great help from PY members that solved some odd problems on my GTO.


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## deanhickey (Apr 6, 2015)

PontiacJim said:


> Lint free rags? What, paper towels or an old rag made from a former worn out T-shirt wasn't good enough? Hairnet? My hair didn't fall out back then, now, a different story. LOL


A few more years and I won't t need a hair net. LOL


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## Ebartone (Aug 18, 2019)

Jim, I know this post is old, but I have to tell you I thoroughly enjoyed your original post! Although I must say I was waiting for you to talk about the connecting rod chamfer being on one side and expected the problem to have been installing it with the non-chamfered side against the chamfered crankshaft. Even so, as a guy who is recently assembled my own engine, it can be terrifying and intimidating! But tremendously rewarding when it works!

I remember when I finally tighten down all of my mains, thinking to myself wouldn’t it be fun to measure my end play. I measured my end play and it came out exactly 0! After a bit of investigation and removing the thrust bearing, it went back to about eight or 9 thousandths. After a few words with my machinist I realized that when he line honed he didn’t completely grind down the thrust bearing cap evenly, so we literally took a small amount of material off the lower thrust. I’m not thrilled about it at all and told him so, but at the end of the day with lots of advice I realized no major harm done, in fact most modern engines only have the upper as a thrust surface. But my point is I would have never thought to look at that without learning from you guys, and tightening it down and leaving it as it originally was would certainly have caused serious damage.

Thank you, and everybody for the education I constantly receive on this forum.


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## Ebartone (Aug 18, 2019)

Yikes, after reading this again I think you are talking about the journal that goes into the main, not the connecting rod, my mistake. But looking at the picture I saw a connecting rod journal. Either way, great information!


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## geeteeohguy (Feb 2, 2008)

Great thread and post. I ran into this exact problem with the rod bearings in the 383 I built in late 2019 for a '61 Chevy I have. The stoker crank had really big fillets which grabbed the edges of the rod bearings, causing the engine to lock up. I found this during assembly, as it would not turn after I installed only two rods/pistons. The machinist I used informed me I needed special narrow bearings, or I could scrape them to fit with a bearing scraper. He showed me the technique and I did all the bearings and it worked out. He actually prefers to hand fit the stock bearings by scraping rather than use the narrow bearings for more surface area. Doesn't take much to lock up an engine!


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