I just wanted to ask all you guys what your thoughts are on bearing clearances? I always wondered if there was an advantage to running them tighter or looser as far as performance and longevity go? I just wanted to hear what you guys think about this and this isnt to find out what the exact specs that you guys are running just a basic pros and cons to running them tight or loose?Thanks this has been bothering me for a while so lets see what we come up with?

 

The factory has a given "acceptable" range of bearing clearance in the helms manual. I like to be on the loose side of that range (usually .0015) on turbo motors. That's what I've used on 3 motors now and I have had good luck with it.

I believe a well known engine builder posted specs of a motor he built here before and his were .0016.

 

as long as the crank has not been shaved, or the block, i've been using factory specs and bearings with no problems.

 

I am presently getting a motor sleeved and built but I was going to actuallt drive the car alot and just wanted to get some info on what is better for the long run?

 

Does anyone else have any suggestions?

 

As a general rule larger oil clearances will increase oil flow around the bearings.This is a good thing until it drops the pressure to much and the oil film can't keep the bearings from touching the crank.To tight and the oil will burn and breakdown from the slow flow.Also slight deformation of the caps can allow the film to be pinched off and allow the bearings to touch the crank.And by the way the bearings touching the crank is a bad thing .The main bearing clearances increase as the block warms up and need to be tight when cold so they aren't to big at operating temp.Dry sump pumps and external pumps can support larger clearances.The stock pumps loose some efficiency when they get warm and expand.The stock recommended clearances are the way to go in about 90% of the engines out there.
Glenn

 

Thanks for the informative post that is what I was looking for . I also just wanted to pick everyones brains for what they have ran as far as clearances and what has worked and what didnt? I appreciate you taking the time to help me out