I have the exact same problem, but from about 2600 to 2900 rpm.
I have 4-1 headers and a stock pipe and muffler (rather old, though).
I have tried a lot of things:
1: Make sure all the clamps and rubber hangers are OK.
2: Underfelt under the main carpet and the trunk mat.
3: Extra soundproofing on the firewall and tranny tunnel cover.
But the resonance is still there. It's especially annoying on the
highway with the hardtop on, since 60-65 mph is right in the range
of resonance.
I can't figure out if the sound is coming from engine vibration,
the main pipe resonating, or the muffler resonating. Maybe adding
a resonator in the middle of the main pipe would help, but
I've got enough other projects stacked up...
Doug Braun
'72 Spit
At 09:33 PM 9/8/01 , Jim Muller wrote:
>Now for my question. The exhaust has a major resonance at about 2300-2500
>rpm. It is quite loud inside the car, loud enough to be a real irritant.
>Is this normal? (The muffler is new, BTW. The previous motorcycle-style
>"straight pipe" was embarrasing. Nigel is red enough to attract far too
>much attention already.) Should I look for something amiss, or improveable,
>in the exhaust hangers? Or is it just something I'll have to live with?
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