cooked spark plug wires

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Apr 11, 2010 | 10:47 AM

RVbud

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cooked spark plug wires

I have a 1989 class A RV with a 460 engine. I have gone thru three sets of spark plug wires in the past 2 years, due to extreme heat melting the wires at the spark plug ends. I had the manifold gaskets removed because the mechanic told me that this engine was not designed to have gaskets. The engine is noisey and it backfires when it is cold, but once it warms up, it quiets down and runs smoothly.
Are there supposed to be manifold gaskets and perhaps heat shields on these engines to protect the spark plug wires?
also, I am told that this engine has a Holley 4 barrel carb set with Calif. emissions settings. Could this have anything to do with the backfiring?

Apr 11, 2010 | 12:10 PM

Bear 45/70

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From: Union, Washington

Your mechanic is an idiot. Yes the 460 came from the factory without gaskets, but unless you pull the heads and level cut the exhaust face of the heads and the exhaust manifolds, they are gonna leak. Always use gaskets with any rebuild. Oh and find another mechanic.

Apr 11, 2010 | 03:57 PM

RVbud

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Thanks Bear. Do you know anything about the california holley carb? I think this is causing the backfire. Or, I have read (here) about Crabby's timing problems. Might that be causing backfire?

Apr 11, 2010 | 05:36 PM

Bear 45/70

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Quote:

Originally Posted by RVbud

Thanks Bear. Do you know anything about the california holley carb? I think this is causing the backfire. Or, I have read (here) about Crabby's timing problems. Might that be causing backfire?

I have a 1984 heavy duty F250 (a light 1 ton) with a 460 and the Holley carb, or I should say "had". The Holley 4180 4 barrel carb is an emissions carb and I tossed it in my carb parts bin and replaced it with a Holley 1850, 4 barrel non-emissions carb that I massaged. Instant 1.5 mpg improvement with across the board throttle response improvement. The 4180 runs too lean normally and if anything goes wrong with it it gets too lean. My theory is to replace the 4180 because all the adjustments are limited and the idle mixture screw are air adjustments and not fuel adjustments, Hence turning them out makes you leaner, not richer. Backfires are almost always caused by too lean, ignition timing way off or valve timing wrong (bad timing chain).

Apr 14, 2010 | 08:44 AM

Bern_F150_4x4

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From: Maryland

RVBud, your truck should have heat shields that cover the manifolds to prevent the plug wire fry that your experiencing. My heat shields are still intact, I can snap a pic if you would like.

In your truck those manifolds will glow cherry red anytime you are on the throttle for an extended period of time i.e. hill climb. You can purchase high temperature thermal sleeves to place on your plug wires to help protect them. I’m not sure if the OEM shields are still available from Ford, this sounds like a job for numberdummy. I would consider getting the shields if you can find um...

Apr 14, 2010 | 09:18 PM

Bern_F150_4x4

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From: Maryland

Here's a pic of the Left side heat shield on my '86. You will notice it serves a dual purpose as a manifold gasket and heat shield. The Right side (no pic) has the same shield and also has the heat riser over the majority of the manifold. Also note the rubber hose over the plug wire, I suppose the PO had issues with cooking wires on my truck too!