Small Backfires With Headers Only

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Jun 21, 2006 | 05:25 AM

scottlane

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From: Ousley, GA

Small Backfires With Headers Only

After putting headers (Headman Elite) on my '74 360 I cranked it up and idled it for about 30 minutes (headers only - no exhaust hooked up). During that time I had several miniature backfires. It all seemed to even out the longer it ran. This morning I was driving it in to get my pipes reconnected and I noticed it again as I decellerated. When I'm on the gas I don't feel or notice it. The 360 runs a Holley 4bbl intake with a Holley 4bbl 650.
It was not doing this before the header install. Is this all due to a lack of backpressure with the headers alone?

Jun 21, 2006 | 08:02 AM

1975Ford

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Is there a header exhaust leak, or the flange on header to head gasket leak?

Jun 21, 2006 | 08:32 AM

scottlane

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From: Ousley, GA

No leaks to the best of my knowledge. Ran a tube from each port to my ear and found one that needed tightening. Still no difference. I'll be able to hear better after my pipes/Flowmasters are hooked back up.

Jun 21, 2006 | 09:35 AM

73Custom

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From: SD

This is normal with open headers. It should not do that once the exhaust is hooked up. If you still notice it, then check for leaks.

Marty

Jun 21, 2006 | 10:04 AM

scottlane

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From: Ousley, GA

Just picked the truck up. Backfires are gone but now I have a rough/fast idle. Acts like a vacuum leak. Couldn't find out where on the spot. My exhaust guy tried to help me find it - in fact, pointed it out to me. None of the obvious spots were the problem.

Jun 21, 2006 | 01:56 PM

LxMan1

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From: Louisville,Ky.

You may have to readjust the idle mixture on the carb now that it's breathing better.

Jun 21, 2006 | 05:44 PM

scottlane

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From: Ousley, GA

I found my problem. The manifold vacuum line had come off the vacuum canister. What an idiot. Now I need to drive it with the vacuum working right to check for any carb adjustments.
Even with the vacuum problem it really gained in power.