Greetings,
Consider this a plea for edification. Why does a car in a reasonable state
of tune buck, snort and shudder (when cold) if the exhaust system leaks?
This summer, I installed a Monza exhaust on my '69 TR6 (Dual weber down-draft
conversion, quick-trip header, real stock and high miles otherwise...). It
ran pretty well, (but much too loud - my head would resonate at about 2800 rpm)
although there was the distinct odor of exhaust fumes in the cockpit with the
top up and the vents closed. No big deal, I thought, just leave the top down,
or turn on the blower. Then about a month ago, I replaced distributor advance
springs (which were really pretty lame) with new ones from TRF. Immediately,
the car ran poorly when cold. I did the usual tune-up stuff: points,
condenser, distributor cap, timing, check & clean plugs, set timing, etc.
Some improvement, but not much. With winter approaching, I thought I'd better
trace down the exhaust leaks, and while at it weld in a muffler to quiet things
down some (I know, I know, so much for free flow, but this is my daily driver.
If it was only a weekend car, I could live with the noise - I couln't even
here the radio or the noise from the layshaft bearings! Besides, I still have
those nifty quad-tipped chrome pipes sticking out the back). So I took the
whole mess off, did some fabrication for the new muffler and checked each
section for leaks before I put it back on. The quality control at Monza is
pretty poor. None of the joints between pipes was tight, or capable of
sealing with clamps! The splitter piece which is made from two pressings
also leaked all around the joint, and at the points where pipes had been
welded to it! So, I seam welded the splitter, and welded most of the joints,
and used an expander to make the others fit well. I'll never buy one of these
again! Anyhow, to make a long story even longer, it purrs like a kitten now,
even when cold - I can even hear my layshaft bearings again.
So why does a leaky exhaust cause running problems? I thought reduced
back-pressure was a good thing.
Enquiring minds...
John
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