Until very recently I had a 4-1 (Pacesetter) header. When I
installed it I took the stock main pipe and chopped off the
front 15" or so, so it could connect to the header via a
2" to 1.5" reducer. Everything lined up well, and I had welded
up a bracket attached to a muffler clamp, so the back end of the
header was bolted to one of the bellhousing bolts
and could not vibrate or flex. Even so, I was bothered by an
annoying booming resonance at highway RPMs (2700 to 3000).
Last spring I bought a flex coupling to try to install, but space
is really tight in the critical area where the exhaust passes
around the edge of the bellhousing. I could not figure out
how to fit in the coupling, and I sort of gave up on it.
Anyway, when I put on my hardtop a last week, I got fed up
with the resonance (and this is with the stock muffler!),
and I decided to try re-installing my stock exhaust manifold,
which had not been on the car in 7 or 8 years. I found
the front piece of the stock main pipe that I had chopped off
when I installed the headers, and welded it back to the
rest of the pipe. Now I have a 100% stock exhaust system.
I found that the annoying resonance was mostly gone, and
there was less noise overall. There is a new resonance at
1100 RPM, but you spend very little time driving with the
engine at that speed, so it does not matter. Also there is
a definite boost in power in the 2500-3000 range.
I am happier now, and the Pacesetter header will be retired.
It's not total junk; at least it fitted OK, went on and off
without being blocked by the engine, and did not crack or break.
Possibly a 4-2-1 header would have been quieter than a 4-1 header,
and have given more power at lower RPMs...
One question: Back when I had the original non-OD transmission,
where was a little bracket that bolted to the back of the transmission
and held the exhaust pipe. (Part #147791) But when I installed an OD
transmission several years ago, I could not figure out how to
re-attach the bracket. There does not seem to be enough space
around the OD unit to fit the bracket in its original location.
Does anybody have a car with OD and a stock exhaust, who can describe
how this bracket is supposed to be fitted (if at all)?
Doug Braun
'72 Spit
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