I just pulled the crank on my B16a project motor and finally got a look at the main bearings. The rod bearings looked good, not so for the mains.

Laid out in position:



The #1 top half (bottom row, all the way to the right) shows heavy wear, all the way through the lining, as does the #3 bottom half (top row middle).

A closer look at #1 and #2 top (block) halves:



#1 (right) seems to show improper seating or oil starvation according to pictures and illustrations I've seen. When you look at #3 though.....



...showing the same kind of wear, but on a bottom (cap) half, I wonder if my crank is bent or if the block is warped. I also don't know the history of this block. Do main bearings in turbo cars show excessive wear like this under massive crank loads?

This wear pattern can also be seen at the very edge of the #4 bottom (cap) half, show here with #3 bottom.



If anyone can help me read into the story these bearings are telling me, I'd appreciate some input.

 

What kind of crank pulley are you using?

Suprdave

 

Oil starvation. I can hardly imagine the block warping. This would happen with extremely high temperatures, and your bearings would have plenty time to melt before it happened. Are you running on stock oiling system?

 

Actually, according to my machinist, a little block warpage is not extrordinary. Mine had some, but was still within spec.

 

thanks for your input guys. I inherited this block, so I'm not totally sure of it's history, but when I got it, it had a stock crank pulley and stock oiling system. I've since gotten a new crank pulley as the one that came with the motor had a chip in it and I didn't think it was balanced.

I'm going to be sure to clean each and every oil passage with diligence. I do think this is an oil starvation issue, possibly improper seating of the bearings, but I think I've got a decent block to work with.

Thanks again for your thoughts!

 

If you had a UR underdrive crank pulley... you could put all the blame on that! Seriously though, what is your driving style? Dragracing? Roadracing? Oil starvation doesn't seem likely unless you're pulling high G's... or let your oil level get low, even once...

 

Well, this is just a block that I bought from someone, so I don't know what kind of abuse it's went through before I got my hands on it.