My motor is assembled and my engine builder and I are trying to pick a pump. He said my bearing clearances were a little big about 25. Should I go with a HV or standard. It's not a stroker motor. It's a 35x. He was thinking of a HV with a low pressure spring. What do you all think?

 

I'd go std. volume with a high pressure spring.

Is that .0025" on the mains, or rods, or both? Don't know for what purpose your engine was built, but .0025 on rods sounds a little looser than necessary, IF a street engine.

 

Thanks for the reply. It will rarely be driven on the street. Maybe a short trip to the local hang out a week. That was main clearances. I definatley wanted it built as a "mainly race" motor.

 

If you go loose on the bearings it's either thicker oil or a higher volume pump. That's massive over-simplification. Rods and mains are only one area the oil can squeeze-past on a small block. Cam bearings are an often-overlooked area. Replacement bearings are usually a little looser than stock. I don't know why this is, but I've found it to be true quite often. Also, the rod-to-rod clearance is another area that can affect oil pressure. If you're on the tight side (.010") you'll use less volume than if it's loose (.020").

If you've replaced the factory cam bearings along with the loose bottom end tolerances you'll probably find that a high volume oil pump will be required if running common light weight xxW-30 oil. Oil pressure on a hot motor at idle will be low if you're running out of volume for the weight of oil you're using.

The small amount of extra HP it takes to spin a higher volume oil pump is probably worth the peace of mind if you don't have the time/money/patience to guess wrong.