In an attempt to meet aesthetic, performance and sound level goals, I have
Frankenstein's exhaust system installed on my TR6.
I have a 6:1 header feeding a y-pipe going to two Falcon SS mufflers. The
muffler feed pipes each have 2 motorcycle baffles inserted. Sounds like an
odd setup, but has given me nice rumble at idle and slow cruise, seemingly
plenty of pull from start and can still talk on the highway. Nice twin pipe
look too. Fuel consumption over 20 mpg. I thought all was well.
However, I'm now chasing down something odd in the form of a lack of power at
higher speeds (80+) . I had the car in the shop last week for a small
re-welding job on the rear frame cross-member that turned into $3K of all
sorts of things up to and including replacing the timing chain and cover. Bet
you didn't know the rear shocks and the timing chain were related did you?
Neither did I...
Anyway the point is that with the timing chain wildly loose and now replaced I
thought I would do a little tuning up. The mechanic had mentioned noticing
that she didn't seem strong above 80mph anymore. So me brother in law and I
grabbed a porto-GPS and headed out onto the highway. Sure enough, I seem to be
having trouble getting the car above 85mph. In the old days when funning, she
would just fly up the scale past 100 at which point I would run out of
driveway and risk running into the yacht floating at the near end of the
swimming pool. (yeah right, just seeing if you're still with me here)
So, I've got regular twin ZS carbs, Crane Cams ignition and Jim S's roller
rocker kit (wearing out it now seems). 25% O/D on the transmission. I noticed
that the weak spot seems to be at around 3000 rpm, so I thought that perhaps
the O/D is making it harder to push up into the power band. Perhaps if I want
to go fast I have to engage it at higher speed. I just don't recall the
problem in the past.
I'm seriously wondering about that roller kit too. Memory says that its a 1.75
setup which Ted Schumacher swears to me is folly. Perhaps that is making
things float at higher power. It's odd, because, as I say the car will pull to
5000+ going up a hill in 2nd and third.
So, before I go nuts changing all sorts of things, I want to find out if the
baffles are choking the engine. Perhaps I was wrong to think all was well
there. Is there some sort of test or whatsit I can use to determine what's
going on in there? Pressure sonsors, mechanicla ouija board etc. I mean the
obvious thing to do is pull out the baffles and hit the highway again for a
test run, but you all know the joy of separating exhaust pipes, even ones made
of stainless.
Your help humbly requested.
Mark
1972 TR6
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