spun bearing ?

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Oct 10, 2005 | 12:24 PM

NXTFAZE

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Melting Slicks

Joined: Jun 2004

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From: NC

spun bearing ?

Hey fellas,

I got a friend that is having issues w/ low oil pressure in his high compression forged motor in his camaro. The motor has about 4k miles or so on it and has a 100 shot on it. He had it torn down and the diagnosis is a spun main bearing. I told him What would be the cause?

Thanks in advance

Oct 10, 2005 | 12:35 PM

frank dupuy

Melting Slicks

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From: Wilmington Ca.

I would look for some answers from the builder of the forged motor. This should not have occured

Oct 10, 2005 | 12:46 PM

NXTFAZE

Thread Starter

Melting Slicks

Joined: Jun 2004

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From: NC

Thanks Frank, I was afraid you were gonna say that.....

Could not having enough oil cause a spun bearing?

Oct 10, 2005 | 01:21 PM

Mitch C

Melting Slicks

Joined: Jun 2001

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From: Davie Florida

Not enough oil and high oil temps can cause spun bears.
Very high RPM can also cause spun bearings.

Last edited by Mitch C; Oct 10, 2005 at 01:23 PM.

Oct 10, 2005 | 01:57 PM

NXTFAZE

Thread Starter

Melting Slicks

Joined: Jun 2004

Posts: 3,413

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From: NC

Thanks guys.....

Just hoping we can find the cause so it doesn't happen again.

Oct 10, 2005 | 04:04 PM

NXTFAZE

Thread Starter

Melting Slicks

Joined: Jun 2004

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From: NC

Just did some more research.....

Spun bearings is not uncommon when revving over 7,000 rpm from what i read from some drag racers..... anyone else have any input.

Oct 10, 2005 | 04:48 PM

RED99

Safety Car

Joined: Jul 2005

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From: Vancouver WA

I'm not sure if you will ever know for sure what caused it. But low oil pressure sure didn't help it. I would advise having the Mains aligned bored before putting it back together, just to be safe. Look at the oil schemtics of the motor, and see which main is on the last of the feed line. If it was that main, then it probably was due to oil pressure lost. How did all the other bearing look? "I THINK".....it's usually it's the Rod bearing that spins.

Oct 10, 2005 | 05:22 PM

GUSTO14

Le Mans Master

Joined: Sep 2003

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From: eastern NC

Quote:

Originally Posted by RED99

... If it was that main, then it probably was due to oil pressure lost. How did all the other bearing look? "I THINK".....it's usually it's the Rod bearing that spins.

Unfortunately the low oil pressure is usually the result of the spun bearing, not the cause. Many times it's the first indication... followed closely by that old knocking sound.

GUSTO

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Oct 10, 2005 | 11:14 PM

Threed

Burning Brakes

Joined: Apr 2003

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From: GOCC - Rebels Without A Clue Santa Barbara, CA

Lots of things can cause a spun bearing including poor clearancing, improper torque or torquing procedure, debris in the crank etc.

Oct 11, 2005 | 12:16 AM

#10

frank dupuy

Melting Slicks

Joined: Jul 2004

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From: Wilmington Ca.

Quote:

Originally Posted by frank dupuy

I would look for some answers from the builder of the forged motor. This should not have occured

Sorry for being so abrupt on my first response. The truth to the matter is there can be many reasons for the crank to spin a bearing besides lack of oil. The only thing to do now is remove the crank while checking torque on the bearing caps. If bearing caps were not torque to specks one probable cause. The bearing is already destroyed but it could have been faulty or burred while installing the crank or just not installed properly. Crank should be checked for any under or over size journals. Also need to check block bearing caps for sizing and alignment. When building up a motor you need to check everything as the saying goes you are only as strong as the weakest link.

Oct 11, 2005 | 01:19 PM

#11

NXTFAZE

Thread Starter

Melting Slicks

Joined: Jun 2004

Posts: 3,413

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From: NC

Thanks for all the input. If I was able to post some pics of the bearings......could anyone tell what was the cause?

Oct 11, 2005 | 04:21 PM

#12

mdhmi

Team Owner

Joined: Jul 2003

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From: Detroit

Who built the motor?

Mark

Oct 11, 2005 | 11:42 PM

#13

7.0sc SuperVette

Burning Brakes

Joined: Oct 2002

Posts: 797

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From: Sunny Earthquake Country, USA On the Left Coast (which is becoming more Right!)

Bearing crush...

Proper bearing crush provides the radial force to hold the main bearing in place. If the line bore was to loose, or the bearing not long enough (transversely) or a machining chip held cap up on torque down, it will spin.

Roy

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