Help with a 390

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Nov 10, 2002 | 07:00 AM

jowilker

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From: Creedmoor, North Carolina

Help with a 390

Guys, a friend has a fresh 390 that is emitting white smoke from the passenger side tail pipe at idle. When he pulls off it clears out, but returns again at idle.

Any ideas or suggestions?

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Nov 10, 2002 | 09:39 AM

1984_355w

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From: Illinois

Help with a 390

If it's real fresh it may not be completely broken in yet. Those rings might be leaking a little oil past and its burning but white smoke sounds like coolant so i don't know. When the engine is cold pull out the dipstick to see if the oil is milkey. If it is you're getting coolant in somewhere. Most likely a head gasket.

Nov 10, 2002 | 11:22 AM

Ratsmoker

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Joined: Feb 2001

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From: Missouri

Help with a 390

My buddies 302 did the same exact thing John. Vever saw water in the oil or oil in the water. I think the motor had about 150,000 miles on it. It could be excess condensation buildup in one of the mufflers.

Nov 10, 2002 | 07:14 PM

1984_355w

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From: Illinois

Help with a 390

Dive it for a while-1 hour plus then see if it still does it. If it does have him change the oil and see what it looks like.

Nov 11, 2002 | 05:58 AM

jowilker

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Fleet Owner

Joined: Jun 1999

Posts: 24,552

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From: Creedmoor, North Carolina

Help with a 390

The first time after a test run, it was driven three hours home. This motor has picked up some gremlins from somewhere. It runs strong like a new 390 should. We had to tear it down because of oil pressure problems and finally found the gasket on the pump pickup didn't have a bolt through one hole, so we had the intake off recently.

I am looking for some brain help with the long distance diagnosis. We are looking to do a rad. pressure test. Just gathering thoughts where to look.

thanks guys

Nov 11, 2002 | 04:33 PM

1984_355w

Elder User

Joined: Jul 2002

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From: Illinois

Help with a 390

good thinking on that. Have them run it up to at least 15 psi. The 302 in my '74 had it pressure tested to 10 and that wasn't enough to make it leak. The problem was it kept losing coolant and i couldn't figure out why. I took it to a different shop that ran it to 20 and it came out of 2 tiny holes in the radiator. It only leaked when it was hot and pressurized and it evaporated so fast on the radiator i didn't know where it was leaking.

Nov 13, 2002 | 05:43 PM

jowilker

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Fleet Owner

Joined: Jun 1999

Posts: 24,552

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From: Creedmoor, North Carolina

Help with a 390

Are all of you guys out in the cold? No ideas here? Darn shame I didn't want to size some headers or something, you'd be all over that.

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Nov 13, 2002 | 09:01 PM

levilevi2

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Joined: May 2002

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Help with a 390

You might want to do a compression test before you go driving much at all. That'll tell you if you have a blow head gasket, which it could be if you have water (white smoke) getting into the combustion chambers. The numbers should be all be within 10-15% of each other or there might be a problem. Two REALLY low cylinders next to each other could mean the head gasket between them is shot.

Nov 14, 2002 | 11:29 AM

#10

William

Logistics Pro

Joined: Feb 2000

Posts: 3,565

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From: Sun River St. George

Help with a 390

John, I'd look at the intake gasket seal at the right front where the coolant flows through. Sometimes the head will be pitted from corrosion and this area will be hard to seal. I would really suspect this problem if the number 1 plug is all nice and steam cleaned. Might try re torquing the intake. If you pull the intake look at the intake port on the head and the intake manifole may find a crack. Let us know what it turns out to be.
William in Atlanta