I'm still playing "Let's get to know the new car" with my '74 TR6, and this
weekend's project is checking/setting the timing. As usual, nothing is as
easy as it might seem at first. Here's what I found:
1) The specs call for 4 degrees ATDC at 800 RPM, which seems *really*
late to me.
2) When I first checked the timing it was close to 6 degrees BTDC at
idle -- a long ways from where it should be. I seem to remember
from my old auto shop days in High School that we'd adjust the
timing with the vacuum advance disconnected, but that didn't
seem to make any difference (neither the Haynes or Chilton's manual
I have said anything about this).
3) In the process of removing the vacuum line I found that there was
no vacuum present in the line. This got me to tracing the line
back to the carbs, but instead I found this funky vacuum switch
in the radiator hose. Further investigation found cracked and
broken fittings on the lines feeding the switch. Using some
old hose from the workbench I was able to past things back together,
but still no vacuum (and yes, the engine was running at the time).
4) I checked the "vapor traps" and found them moderately difficult to
blow through, so I tried bypassing them. Still no vacuum.
5) Finally, I bypassed the whole mess and connected the distributer's
vacuum advance line to the vacuum line coming off of the carbs.
Ta da -- the timing shifted several degrees.
6) After setting the timing the engine idled quite a bit better, but
it tends to backfire at low RPM when you rev it (once it gets going
it seems to be OK).
So here's some questions:
- Is 4 degrees ATDC legit?
- What do the vapor traps do? Catch condensed fuel?
- Why the hokey vacuum line configuration? Is the switch in the
radiator hose supposed to shut off the vacuum advance while the
engine is cold?
- Are the connections to the radiator-hose-switch critical? The owners
manual showed a different arrangement than was presesnt on the car,
and the TRF catalogue detail showed a three-port switch (mine has
four) in yet another configuration.
- What about this backfire? I seem to be suffering from an illusion
that I own a sports car and that I can go zooming off in to the
sunset, when in reality the best I can do is "cough, cough, POP,
Brrrrrrrrroooooooooom". Surely there's something I can do to coax
a little more "zoom" out of the car?
- Finally, how hot should I expect this car to get? It never gets over
the half-way mark on the guage, but the engine compartment is really
baking.
As always, thanks for the help and advice.
Ron
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Ronald C. Hood U S WEST Advanced Technologies
hood@uswest.com Boulder, Colorado
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