390 noise

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Apr 9, 2012 | 09:29 AM

jman68

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Joined: Sep 2011

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From: Lakeland

390 noise

I have a 66 F-250 with a 390 in it. It has developed a noise that I can't seem to diagnose. Once the engine is warm, if you let off the gas at about 40-45MPH to maintain that speed, there is a wrapping noise coming from the engine. At idle I hear nothing and while accelorating I hear nothing. Any ideas what this may be and where to start? Thanks.

Apr 9, 2012 | 09:52 AM

1972RedNeck

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From: Townsend, MT

It may be backfiring on deceleration? What is your timing set on? I would set your timing on 10 - 12 degrees and see if that fixes it.

Apr 9, 2012 | 04:48 PM

daveengelson

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From: Boulder Creek, Ca

Might try blocking tires w/ tran's in neutral see if able to observe from under the hood. Wonder if belt, or pulley acting up at a particular rpm.

Apr 9, 2012 | 07:23 PM

Wyatt66f100

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From: Milwaukie, Oregon

Wrapping noise? what does a wrapping noise sound like?

Apr 9, 2012 | 07:51 PM

daveengelson

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From: Boulder Creek, Ca

Quote:

Originally Posted by Wyatt66f100

Wrapping noise? what does a wrapping noise sound like?

Curious myself!!

If it's a 'wrappping' as in back pressure from exhaust agree w/ redneck. Not an authority, but seems it could be timing; although, did have a simular issue and turned out to be carburation, believe due to my setting mixture too rich and it was dumping excess fuel into the hot exhaust manifold.