minumum bearing clearance?

[dlampe]

What is the minimum bearing clearance for the rods and the mains on a 600+ HP 427 SO? I am having my new motor rebuilt after a problem that is yet to be determined that resulted in a spun rod bearing and damaged mains.

[Excaliber]

George at Gessford made an interesting comment about that concerning my crank. He said be SURE to tell the local machinist here to grind the crank to the "small side" of the specs to insure enough bearing clearance!!!! Seems to me that .0015 was barely "acceptable" and .002 was better.

After using the "mic" I also used Plasti Gauge, just to double check my work. Some people don't like the Plasti for anything, to each his own! I say, "Can't hurt to double check" everything.

[Keithc8]

The problem with most ford engines is that they have larger main and rod sizes than most other engines. I will assume that you are running the standard size Ford rod journal and not the BB Chevy that is used a lot on the after market rods. I like to see about .003 to .0035 on the mains and .0025 to .003 on the rods. On drag race engines only I have even had .004 mains and .0035 rods but that is a little loose for street. The clearance may not have been the only problem as there are some oiling issues that need to be addressed. I like to use a dial bore gauge to check the clearance and set the dial bore gage with the mike that you miked the crank with which will give you the difference in the rod size and the inside of the bearing. The bearing clearance will get bigger as you go to the parting line. The reason for this is that the bearing company has built extra clearance into the bearing because the bearing bores are stretched into a oval shape under power just a little and pulls the sides in thus the reason for the extra clearance. If your bearing checks .0025 straight up and down, it will check about .003 to .0035 as you rotate to the parting line. Good luck, Keith Craft