Bearings Report - 3.2L, 100k+

[Yamaha V6]

Just wanted to pass along another bearing report.

The 3.2L I'm building for a customer (not you Jim... wink ), exhibited rod bearing wear, copper showing but no burn marks, on the uppers. Minor wear in comparison on the lowers. The mains were in very good shape.

This was a 95 3.2L with approx. 100k on it.

Ding! Fries are done!

 

[DavidT]

Obviously, I am not a mechanic (as you will be able to tell by my question) , but...
1. When one replaces rod bearings, do you have to look at main, upper, and lower bearings? (3 different sections?)
2. if there are 3 different areas/ types of bearings, can you describe it?

 

[fredhurderjr]

The crankshaft is round. In order to fit bearings in, they are in half-circle shapes - one upper half, one lower half, for each of the rod & main bearings.

The main bearings were nice, upper & lower. The rod bearings showed wear on the upper halves, but not so much on the lower halves (as expected - the engine rams the connecting rod & upper bearing half down onto the crankshaft as the cylinder is fired).

Letting the people know that you need to replace the uppers & not just the easy-to-get-at lowers is all.

 

[cRaZySHO.]

Fred I'm curious, which cylinder showed the most wear? I wanted to see if maybe there is a pattern among worn rod bearings. I know this is 3.2, and mine is a 3.0, but who knows. Mine was the number two rod/cylinder.

 

[Yamaha V6]

Cylinders 2 & 5 were the most, 1 & 4 next, then 3 & 6 with very little copper showing.

 

[MeShoHorny]

What would be interesting would be to compare similar mileage rod bearings on a 3.2L and a 3.0L. If lugging a motor wears bearings then I would think that the wear on the 3.0L would be much greater.

 

[drivinhard]

All things being equal, I've tended to find the 3.2L motors seem to be a little harder on the rod bearings than the 3.0L. Dunno if it's due to the extra torque of the 3.2L, or the weight of the heavier rod/pistons, or a combo of both.