I just recently had my main bearing tunnel align honed because the caps were out of round. I think that the machinist may have taken off too much metal. I told him that the block was going to be boosted and making about 400 hp, so maybe he intentionally did this for extra clearance, but he did not mention anything to me about it. Using blue main bearings (the thickest ones Honda makes), my clearances would be around 0.0022" The acceptable range stated in the manual is 0.0009-0.0017" and the service limit is 0.0020". So my question is, is it common and acceptable to run 0.0002" more clearance than the service limit? Should I take it back and have him fix it, or trust that he knows what he is doing? Thanks for your input!

 

You will be fine with that clearance, Just use 20w50 oil.

 

Alright, thanks for your advice. I am also concerned that the holes are still out of round. The measurement from my dial bore gauge can differ by as much as 0.001" depending on which direction I measure the diameter of one of the holes. From what I hear, the out of round limit is 0.0002". If the bearing tunnel was just honed, should there be any deviation in my measurements depending on which direction I take them, or should the readings all be EXACTLY the same. This is my first time doing internal work like this, so I don't know if I am being too picky or not.

 

All the holes are not going to be measured exactly the same as long as you are within specs then you are good to go.

 

Ideal stock is considered to be 0.0015", and ACL race bearings (or equivalent) are designed for an extra thousandth. 0.0022" isn't a problem, the motor will last a good long while, it's just not a clearance typically run on a street motor.

 

I don't mean that each hole is a different size. I mean that the diameter of the same hole differs by as much as 0.001" depending on where the measurement is taken.

 

most of my main bearings tolerances are between .002 and .0022 i dont have any issues with it