Bearing problems

[crensinivon]

Alright so rebuild number 2 has died after running beautifully for almost 3000 miles now.

The car still has good oil pressure, but it has spun a rod. I'm at a loss, so now I'm turning to you guys for thoughts on why it keeps happening.

For starters crank was uncut just polished, all connecting rods looked good, and oil pressure has been impeccable. Plastigauged everything as it went together, and everything was right in the middle of spec. I used ACL bearings the aluminum silicone ones, could these bearings be the cause of my nightmare? Tuesday I am pulling the motor and inspecting the damage, I can't imagine it to be more than another crank and set of bearings. I just don't want to have to do this a fourth time.

 

[Freerevving]

Alright so rebuild number 2 has died after running beautifully for almost 3000 miles now.

The car still has good oil pressure, but it has spun a rod. I'm at a loss, so now I'm turning to you guys for thoughts on why it keeps happening.

For starters crank was uncut just polished, all connecting rods looked good, and oil pressure has been impeccable. Plastigauged everything as it went together, and everything was right in the middle of spec. I used ACL bearings the aluminum silicone ones, could these bearings be the cause of my nightmare? Tuesday I am pulling the motor and inspecting the damage, I can't imagine it to be more than another crank and set of bearings. I just don't want to have to do this a fourth time.

Main thing is the #2 may be out of round

try some clevites or acl race... they are made with three layers especially to take shape for rebuilds... but it's not going to help if your journal is out of round

 

[crensinivon]

Well the machine shop that turned it checked all tolerances, and I plastiguaged it in two different locations. Guess I'll know more when I take it out. What is the weakest link in the bottom end? Apparently something isn't right. Just trying to make sure it doesn't happen again. It ran so well and so strong.

 

[Freerevving]

well if the journal is round on the crank, then I would check the inside diameter and roundness of the rod

you might want some better bearings to be safe, it may be the way you're priming/ breaking in the engine... the better bearings help take shape with initial start-up... Also check to see of any oil passages are clogged