Installing new bearings with motor in car. Ever run into this?


Three of a Perfect Pair
May 24, 2001
I started out doing a rear main seal and when I dropped the rear cap,bearings didn't look so good.
Appear to be water damaged.
60k on motor.
Anyway,I took all of the mains out and to my suprise,numbers 1 and 3 are .001 and 2 and 4 are std.
Ever run across this.
I know why this was done just seeing if anyone else has seen this.
By the way,they are stamped GM on them.
I will also be doing rod bearings while I'm under there.
The bearings were fitted to the crank individually. I don't believe that was standard GM practice though. Nothing wrong with that, just means someone was paying attention when your motor went together.
IMO, just pull the motor. That way you can clean it up and do what you have to do standing up rather than laying on your back. I pulled my motor in the GN at 64Kish, replaced the rod and cam bearings, put a cam kit in it w/ timing chain, and basically cleaned everything up and slammed it back together. 3200 miles later shes still kicking. Just my .02
Originally posted by Jeff Harrington
This is real common, the rod bearings are that way also. Sometimes they even use five and eight tenths under.

I've always wondered how GM could get such tight tolerances...
I did bearings and rods while motor in the car. It sucks, but can be done. that crank can get heavy when going back in. If you can just pull the motor it would be easier. good luck.
Few things to add.

jetmech, you don't need to take the crank out to do bearings.
That makes a small job into a BIG job. :D

Nashty ,please don't take what I'm about to say the wrong way.
I am not putting GM down but the reason there is mismatched bearings is because GM's machine work during the 80's, sucked. Plain and simple.
If everything was done (machined) properly,there would be no reason for .001,.005 ect.
My bearings also have major signs of bad align bore.Also the tops are just as worn as the bottoms.

8UWITH6 ,I wish I had the money to pull it and rebuild it. That is the right way to fix this.
To do it right I would need over 3k to start. :( Then one thing leads to another and there goes another 3k,4k,ect. :( Front mount,turbo,injectors,heads............on and on.
I also have been getting a lot of KR even with 104 unleaded and 17psi.
Found out why.........Rods have WAY too much side clearence and are slapping around in there.

I really just posted this to get an idea how many people ran into the same thing as me.
Thanks for all your comments fellas.I will be installing the mains this weekend and if anyone is interested,I will let ya know how the clearences worked out.
I ordered a set of std and .001's to try to get this close anyway.

PS....anyone know why if I don't post for awhile,my post count goes down?:confused:
I had well over 180 now it's 80?
I fully understand your 3-4k concern of an engine pull. I just did my 4K rear main seal myself :D. Having said this though, I would without question, pull the engine with the intention of merely changing the bearings. If the crank is round you could be all done the bearings on day one and just have to put it back in the next. DO NOT drink a few beer in the garage while looking at it on the stand...very hazardous to your wallet. I think the entire job would litterally be alot cleaner on a stand compared to in the car.
Just my opinion.
I would have to agree, I'll pull the motor to do head gaskets.

I would never imagine monkeying around with the bearings in the car.

Because it's such a small package you don't even have to pull the hood. :cool: