Odd Main Bearing Issue

blacksix

Member
Joined
May 15, 2002
Pulled the pan on a buddy's new TTA tonight to change the rear main seal for him and clean out the pan/pickup. He had blown a headgasket due to a faulty fuel pressure regulator and I wanted to check the bearings anyways.

I found all the bearings to look worn but not what I would call surprising (by my standards, which are admittedly low) - - except the rear main, worn right down to the copper. Thrust surfaces are fine, crank is a wee bit rough but OK.

Anyone seen this before? What might be the cause?

I think those spots on #3 cap bottom are from cap walk, is that correct?

Mains.jpg
 
Detonation?? [I doubt that happened when the reg failed. That's happened repeatedly, before this failure]..Is there any such indicatons on any other caps? Brg shells loose in the caps?
Looks like the engine has had considerable dirt pumped thru it...Hi miler?
Is this the first time it's been apart? If not, what sizes are on the brgs? Undersized? [Reason I'm asking, that rear looks to have been run too tite.]
 
OEM shells, none loose. Have to peel the shells out tonight to check that rear one, the center and rod appear to be original, or at least have GM numbers with no sizes.. Oil pan was sludgy, although it had a blue gasket so has been off at some point. Almost all indicators show 67,000 miles, car is very clean except for the steering wheel . . . ???

Last photo shows (poorly) some white spots/blotches on the crank & rods . . .

June 5 001.jpg
June 5 007.jpg
June 5 010.jpg
June 5 008.jpg
 
Detonation an possibly oil starvation. The rear main is the last bearing to get oil. If the timing cover was ever tore apart ad the pump not primed, then that may have killed the rear bearing on start up. Cap fretting is indication of poor tune up. (detonation) Might want to pull the crank and do it right. (polish the crank and install .001" undersize bearings if needed) Check the big end of the rods for roundness/ovaling, too.
 
Detonation an possibly oil starvation. The rear main is the last bearing to get oil. If the timing cover was ever tore apart ad the pump not primed, then that may have killed the rear bearing on start up. Cap fretting is indication of poor tune up. (detonation) Might want to pull the crank and do it right. (polish the crank and install .001" undersize bearings if needed) Check the big end of the rods for roundness/ovaling, too.

This sounds a lot like pulling the engine . . .

Didn't pull the front cover but it does have metal gears as opposed to plastic (scratched in the distributor hole with a coat hanger.) Did the TTA's come with steel gears and no tensioner, or has someone changed it?
 
What does the stamping on the back of the insert read?
 
This sounds a lot like pulling the engine . . .

Didn't pull the front cover but it does have metal gears as opposed to plastic (scratched in the distributor hole with a coat hanger.) Did the TTA's come with steel gears and no tensioner, or has someone changed it?



TTAs were just like the Buicks... plastic .. Someones been in there before.
 
Pull the the top and see what you find
 
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