I'm using tape on the downpipes of my BJ8. The tape works well at keeping heat
in, no question. My car's exhaust is pistol hot at the tail pipes (that's heat
that isn't being dissipated in the engine bay). I believe the engine runs a bit
cooler for it.
I posed this question to the List and some said the tape traps moisture but
that made no sense to me because any moisture (e.g. rain) on hot exhaust parts
get evaporated immediately (plus, I sprayed high-temp silicone sealant on the
tape and it appears to make it waterproof). I read an explanation in hot rod
magazines that seems more logical to me: the heat retained in the manifold or
pipes is more than mild steel or cast iron can endure and the parts
disintegrate from the inside out (the hot rodders call the effect on headers
"mummification"--probably not doing much good for my glasspack mufflers,
either). The ceramic coatings--e.g. Jet-Hot--supposedly handle this problem by
coating inside and out.
I can't vouch for the ceramic coating as I haven't used it (yet), but others
probably will. If you do wrap your manifold you should wrap your downpipe as
well, as the gas passing from a hot to a cooler, denser region will encounter
increased back pressure (or so it was explained to me by a Jet-Hot rep).
Bob
What is the efficacy of using exhaust manifold tape to decrease
heat under the hood of an AH BN1? Is there a particular kind of tape
better than others?
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