Bearing wear

[larrym]

I got the crank out and did a visual inspection, when I pulled the main caps 2 & 3 where worn quite a bit 1 not so much and 4 was starting to appear bad. The connecting rod caps all looked pretty good, lifted out the crank and the bearing wear is the opposite of the caps. This shows all the load areas are showing lots of wear (main caps and top of connecting rods) normal I guess I'm curious why the front main bearing would show more wear on the block than the cap did. My cam bearings look good as did the cam and cam thrust surface so I don't think it was an oiling problem.

The motor was gone through before I bought the car my oil pressure was good until recently when it started to drop once it was hot. You can see that some of the bearings got hot at some point. hear are some poor pics of the main caps. I'll get pics of the rods and post those too.

 

[larrym]

More pics of bearings in the block.

Couple of rod bearings the one that got hot is number 5 one of the last to get oil maybe it was ran low at some point??

 

[Chuck Leeper]

My $.02

"I'm curious why the front main bearing would show more wear on the block than the cap did." The timing chain may have enough load on the crank to put the majority of the wear in the top 1/2 of the main brg.

Too tite, dirt, dry start when new....??
Looks like the cap parting faces are fretted...Detonation?

What does the crank look like? I've seen cranks that were polished in the wrong direction take out brgs...
[See pge 19 in this link.]
http://www.engineparts.com/publications/CL77-3-402.pdf

Other pages have good info, also.

 

[larrym]

That makes sense never thought about the chain I'm going to drop the crank off and hope a polish is enough. The only real bad spot is the rear main journal I measured the journals and it appears the rods where 20 under and the mains 10 under. Hope I caught it soon enough and I can polish it up and throw it back together.

Then I can pick up the standard block my buddy has and start collecting parts for my stroker :biggrin:

 

[WS6]

Yeah, I agree, it looks like cap walk. I think your crank "has" or "is" flexing.

 

[bison]

You better check all those clearances with the bearings looking like that. Those rod bearings are too hard especially for a stock crank. Cap walk wont cause that kind of wear on rods and mains.

 

[WS6]

I was thinking crank flex caused the main bearing wear on #2-#3 and caused the cap walk transfer too.

 

[bison]

I was thinking crank flex caused the main bearing wear on #2-#3 and caused the cap walk transfer too.

Not at his power level. The rod bearings wouldnt look like that either

 

[WS6]

Even if it was detonating? or pre-ignition?

 

[usetaboost]

It could be from detonation

 

[larrym]

well the machine shop said that the excessive wear on the front cover where the nylon cam button could account for part of the failure. The button wore a depression that i could stack a couple of dimes in. They told me I was lucky the rods need a polish and the mains ground .010. Should have the cover and crank back by Friday .

If I want to go to main studs do I have to line hone the block? I have heard conflicting answers the caps are located by the register in the block how can the fastener affect alignment?

 

[usetaboost]

I would at least have it checked. With original caps you may not have to.

 

[KL Mallender]

I would be curious about the balance of the rotating assembly, anytime there are counter weights at the ends of a shaft, it doesen't take much imbalance to induce some bad harmonics(forcing things to move around more than normal)
And remember, these engines were factory balanced for optimized usage under 5000 rpm so that "We" dont feel the V6's inherent shake/cycle.
Good luck.

Kevin.



ps: you might want to also check the condition of the camshaft bearings, I'll bet #1 is not going to look good.

 

[jarredsoon]

Hey guys I am wondering how come the original poster can't simply install new bearings since the motor is apart and the cost of bearings is minimal? If this is the result of detonation wouldn't new bearings and a better tune solve his problems?? I am no expert just want to learn a little. Thanks
Jarred.

 

[larrym]

Thats all I'm doing just getting the cran cleaned up first.

 

[ek02]

As to the wear on the front upper main bearing, I have seen this on small block Chevys with A/C and V belts for years. GM made a .001 oversize upper bearing half to lessen the knocking caused by the wear. Not sure if a serpentine belt would have the same affect, but it might be the reason for the wear along with some crank flex.

 

[bison]

He could put new bearings in but without knowing what happened and corrected why it happened it will probably happen again. I havent seen one clearance posted yet. Chances are the turbo has swallowed a lot of metal also.

 

[larrym]

I'll have the crank back on Friday, machine shop said everything should polish out. Rods expected to finish at 30 over mains at 10 over.

I'll post the clearances when I get everything back, any other words of wisdom? The speculation the the front cover wear was a contributing factor makes sense and who knows how this engine was maintained prior to me getting it. I do know the tune was out to lunch when I got it and my learning curve could have added stress. I keep an eye on the knock gauge and the wide band that I added plus a temp gauge and oil pressure. Its not an all out race car but sees an occasional trip to the track (once a year)

I hope the turbo is ok its new..... shaft play if any is minimal and the old 6131 I pulled when installing the new one of was sloppy......

 

[chriss4655]

Can antfreeze in the oil system cause bearing damage? I heard if you pop a headgasket with anti freeze in the cooling system you need a complete tear down and clean up!

 

[larrym]

Yes it can that's why you run straight water and water wetter. I put antifreeze in for the winter but drain it in the spring.