The dual pipe system does NOT increase horsepower. Even Newman's SCCA winner
ran a single pipe when we saw i trun several times at Riverside and at
Atlanta. The area of the single pipe presents less wall drag (backpressure)
and more total flow. And the factory HP rating at the port of entry (not in
the sales brochure) actually went down 4 HP in the '72 and later dual pipes
emissions tests (Some of which was strictly emmissions de-tuning of course).
Which was fine for the Federal Eagles. But in a stock engine...you will not
know the difference...except in your pocket book. Price out a single pipe and
dual pipe system and then also look at the complexity of getting out a blown
starter motor..single vs double...or the differential...single vs double. My
vote..get a single pipe manifold. Dual pipes sound like a good idea but they
get mixed as one pipe at the muffler baffle anyway. Cut one open. That's why
you pass smog only on one tail pipe sniffer...not by measuring both. The one
is a sound , acoustic , pressure balancer...much like the old "H pipe" or
yore...but buried in a can. Hope that helps. P.S. For those future
differential and starter and drive shaft repair...DON'T weld it!! Use slip
joints and good grade stainless clamps. MAkes life sooooo much easier for the
DYI repair down the road.
Bill Burroughs, So West VTR National Rep, 70 TR6, 68 TR250, 59 TR3A,
73 MKIV, 69 GT6+ and two 65 TR4A Vintage Race cars. Happy Motoring!
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