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Old 04-04-2011, 09:54 PM
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Cadillac rod & main bearing clearances

I'm kind of in a quandary...I need a guy with some Cadillac 472/500 experience. I've never built a big Cad before and on the hiperf. Cad forum I've been looking at all of the engine builders say that they use the .001 per inch of journal rule. Well the crank has 2.5" rods and 3.25" mains which means a LOT of bearing clearance. The feeling is that the journals are BIG and produce a lot of heat....hence the big clearances.

Now the problem I might have is the machine shop I'm dealing with is highly recommended and does very good work...on Chevys, Fords and Mopars. I've had a couple of discussions with the machinist and he just flat doesn't believe that these big clearances are necessary with a 10-10 crank. I may just end up pulling my parts until I can really verify the clearances but again I really don't want to pi-- this guy off cuzz he's about the only game in town here......anyone with the real knowledge?

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Old 04-04-2011, 10:39 PM
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I don't see what being 10-10 has to do with it. Stock journals are 2.500/3.250. 10-10 journals are 2.490/3.240. They're still huge.
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Old 04-04-2011, 10:41 PM
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I have no experiance with Cadillacs, but I've been racing big bearing (3.25/2.25) Pontiacs for over 45 years. With the GM gear to gear oil pump they have always been hard on bearings until I started running a geroter type Titan oil pump. I put over 150 1/4 mile passes on my 474 w/.0025 rod clearance and .0036 main and the bearings looked good enought to put back in....if the block wasn't starting to split. I don't know about the Cadillac pump, but the Pontiac pump just doesn't have enough volume for high rpm's with the big mains.
I have since gone to an aftermarket block with 3" mains, but I still have a Titan pump.

Bill
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Old 04-04-2011, 11:06 PM
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Yes Tech and WD thanks for the quick replys, my problem is the machinist and I have agreed to set the clearances at .002 rods and .0025 mains and he thinks thats still too big. Do either one of you see aproblem with these clearances? This is a street rod engine that will see a 5000 rpm blast every once in a while.
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Old 04-04-2011, 11:39 PM
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.002 and .0025 are definitly not too big. Just make sure you have adequate oil pressure and flow.
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Old 04-05-2011, 12:22 AM
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Thanks again and I agree, I think he's just used to running a little 302 Ford with very tight clearances. New Melling pump, the big Cad's don't put out a lot of oil pressure...35 at high idle to 50-60 psi, of course depends on rod side clearance...weight of oil etc.
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