Burning Spark Plug Wires

[geodude1958]

We are newbies to the Airstream RV world, having sold our 1971 Overlander. I just changed my spark plug wires, since they were toasted, then took a 700-mile trip. Now the new set are also burned severely. I have heard about "exhaust manifold heat shields" but I don't see anything like that on my vehicle. I am putting on high temp heat shielded wires, but I need to know if I also need heat shields. Can someone shed some light? What do these things look like, anyway? Any help would be appreciated.

[TomW]

Welcome to the forum.

Could you be more specific about where the wires are burnt? A picture would help immensely if you have access to a digital camera.

Tom

[geodude1958]

The wires were burned through on the bottom side. I neglected to mention that at least six of the eight wires were burned through when I first replaced them. Almost all are burned now (by feel). I don't think there is a heat shield on the engine. I had replaced the plug wires (as well as plugs, distributor cap, rotor button) as part of a tune-up to hopefully correct a backfiring problem and loping idle. After replacing he wires, I test drove the RV and it was great, no loping and no backfiring and good hill climbing. On my recent trip from GA to Washington, DC, the backfiring returned, I noticed a clicking sound on acceleration, and when we were approaching home, we got down to 15 mph on a steep hill. After reading some posts, I checked the spark plug wres and found them toasted.

[geodude1958]

Sorry if I am confusing. We are now in a 1993 Land Yacht motorhome. This is where our plug wire problem is.

[TomW]

Sorry if I am confusing. We are now ...

Oh no - that excellent post (to which you responded) went away

The points raised in it were pertinent to your situation.

Wires can burn in a tow vehicle or MH.

Tom

[ALANSD]

Your wires burn from the heat of the exhaust manifolds, very common problem. You can use a metal shield that goes around the plug, but a better solution is ceramic spark plug wires like those available from Jacobs electronics, thru many hot rod sources like Jegs, etc.
These are pricey but last forever. You can also use high temp wires from Accel, although they may still eventually burn--- I wrapped my Accel wires in the aluminum tape you get at Home Depot, and with a few wraps on the two outer wires that are a problem, they have been safe for many miles now.
Also if you have a exhaust leak it will burn the wire right above it, and may need a donut or gasket in the manifold, if it is not cracked.


Consider coming to our local Forums Rallyin Octber- since you are nearby- (check the forums rally page) there will be a number of us AS Motorhomers there

[smily]

Your heat shields are MIA. They were there to begin with . I would venture to say that your manifolds have been removed and reworked or new manifold gaskets have been replaced. You may see evidence of that if there is some sealing compound around the manifold where it meets the block.

Let me tell you a fact, THE WIRES CAN CATCH FIRE!

Read "the yacht has landed" and read on. Been there and panicked that!

see it here

http://www.airforums.com/forum...t=yacht+landed

Oh, and ceramic plug wires, around 150 dollars plus a set or 3 dollars for each heat shield x 8 = 24 dollars, labor is on you. You can always wrap with heat resistant wrap that you find at high performance auto parts stores.

[87MH]

Originally Posted by geodude1958

...We are now in a 1993 Land Yacht motorhome. This is where our plug wire problem is.

AlanSD above may have hit on a real problem.

There have been more than one or two cases of cracked manifolds, broken gaskets, broken studs, or uneven mating planes....any one of which would throw a bunch of heat on one or several wires.

Some of the above problems may well manifest themselves only when hot and under a load - making a static inspection difficult - and uncomfortable.

I had a couple of burnt wires when I first purchased the 345 - I installed a set of Taylor 409's with the asbestos (fiberglass?) heat shields on the plugs.

The Taylors solved my problem, but you should really get the possibility of an exhaust leak checked out prior to investing a bunch of money in a set of premium wires.

If you have to remove/replace the manifolds you might consider getting a set of headers to replace the manifold....I don't know what type of manifold you have on your motor, but the "solid cast" manifolds were prone to have problems due to the expansion with the high heat load of the Motor Home application.

Do a search on "header" or "manifold replacement". Several Forum members have made the switch - SWebster has written a few replies to threads on his recent header job.

[GlenCoombe]

Summit Racing has a good deal on ceramic coated headers from Headman. That and new high temp wires will give you a much more robust engine. The old manifolds are just a poor idea. They crack and the gaskets are always in need of replacing it seems.... then there's the donuts. The first thing I do on a P30 is to change it over to Headmans.

[ALANSD]

protection from heat is a good starting point on all of our coaches before any long trips. The best moves I made were replacing the starter with a high heat resistant, and covering all my wiring in thermal wrap, as well as buying high temp spark plug wires. Also using a coolant additive to pump up the protection on the radiator, it runs much cooler now in the hottest conditions.

[mcneon]

I'd highly recommend plug boot protectors from Summit Racing.

The original metal heat shields are also still available from GM, P/N 465840. After a few years, these are probably rusted away or have been discarded.

The combination of these two parts should eliminate all heat-related spark plug wire problems.

I use the metal heat shields and a variant of the Summit boots on my motorhome and on my racecar, and I never have any problem whatsoever with heat damage.

Bob