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Gearnut
12-08-2007 15:47:18
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Re: .040 bearings for farmall M in reply to L.C.Gray, 12-08-2007 11:25:51
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I've built engines for 30 yrs and no one is wrong in what they are saying. However, I can tell you I've disassembled older engines and found bearings that were shimmed from behind and the bearings survived just fine. I've filed rod and main caps to get the fit I want "by feel", (without using plastic gage). 4100 Cadillac engines were notorious for noisy mains. I hand filed most every main to get it tight. Here's a interesting one, I disassembled a 350 chevy out of a Grumman van that had a constant rattle at 2500 rpms- sounded like a rod. One of the big ends of the rods were .007 over from the factory. The bearing looked perfect (at 75,000 miles!), even tho it probably had little if any crush holding it in place. If you were building a 10,000 rpm engine- I'd say do it to exacting specs. In the case of this low rpm, big bearing engine, you can get away with a lot. I'm not telling you to do it, but if it was me and I didn't want to chrome up the crank, I'd file .010 off each side of a rod cap and see how it feels once torqued up. Side clearance will not be correct, but who cares. What matters is it doesn't have too much end clearance (up and down). You will crush your bearings down and it may even squeeze in a bit at the parting lines. If you can work with the rod only(no piston) it will help. Hope this helps, and now I will go put my helmut on as I'm sure I'll have 20 people all saying I'm nuts. Go ahead..lol. Oh, and it will effect oil pressure slightly as the hole passes the parting line the oil won't have as much to push against with the added .010 side clearance, but once again, it may not really matter so long as you have 30 psi hot at high idle.
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