Help Please, Main Bearing Clearance

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Oct 1, 2006 | 09:13 PM

Just Enough

Thread Starter

Burning Brakes

Joined: Nov 2004

Posts: 988

Likes: 4

From: Livermore CA

Help Please, Main Bearing Clearance

I'm assembling my motor and I plastigaged my main bearing. The numbers I get are the middle three mains are at .0030 and the front and rear are at .0040 inches with ARP studs torqued to 60 foot-pounds, bearings lubed, SpeedPro coated bearings. The shop manual says .0018-.0022 or something close to that. Is my .0030 to .0040 too much?

Thanks, John

Oct 1, 2006 | 10:32 PM

cruisemon

Melting Slicks

Joined: May 2000

Posts: 2,498

Likes: 4

From: Brentwood TN

Quote:

Originally Posted by Just Enough

.0018-.0022 or something close to that? Nominal is .002. .0030 is 50% too much clearance. .0040 is double the recommended clearance. Yes it is too much unless you run higher viscosity oil with high volume, high pressure oil pump. .0040 with 5w-30 and a stock oil pump is a bad idea. .0030 with 5w-30 and a stock oil pump isn't much better.

Clean the bearing cap mounting surfaces and seats thoroughly to be sure there isn't the merest hint of anything on any of them, including lubricant. Torque the mains again and check the clearances again. If they still check .003 - .004, see sentence 3 above (still not the best idea) or have the crank ground .010 and buy undersized bearings (assuming it's okay to do so).

Charlie

Oct 1, 2006 | 11:54 PM

99FewteRC5

Burning Brakes

Joined: Sep 2005

Posts: 1,208

Likes: 2

From: Long Beach CA

clearance should be checked with dry unlubed bearings

Oct 2, 2006 | 12:28 PM

cjs27410

Pro

Joined: Nov 2003

Posts: 503

Likes: 1

From: Greensboro NC

I don't trust plasti-guage. I use a micrometer and a bore guage.

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