A '73 TR_6 was originally timed at 4 Degree after top Dead Center with the
vacuum retard connected and working. With the retard disconnected, the "static
timing", ie. with the engine NOT RUNNING will be at around 12 to 16 degrees
BTDC. With the engine at an idle speed of around 750 -800 RPM, and the retard
disconnected, the ignition timing with a light should be about 18 degree BTDC.
With the engine accelerating up to about 4500 rpm, the timing should advance
to 34 to 36 degrees BTDC. You MUST run at least 91 octane gas in this engine
or you are likely to damage internal parts. The higher the octane the better.
Remember, in 1973 gas was rated differently, It was "Research Octane" and the
number for a TR-6 was 98 octane. The current rating system uses a number 5
lower, so the current version of the same performance would be 93 octane. You
have raised the compression, the engine now wants even higher octane gas!
In tuning a car, you always set the valve lash, then the timing, then
adjust the carburetor idle speed and mixture. The Emission Control Stromberg
carbs that came on your car cannot be properly tuned by the methods that you
mentioned. When they are set correctly, raising the air valve will always
cause the engine to stall. The needles and mixture was set up by the factory
for passing emissions tests, not for performance. The jets must not be worn,
the needles must not be worn, the fuel levels must be set to the proper
height, the idle speed must be correct. The temperature compensators must be
in good working condition, and the idle "throttle by-pass valves" must be
working properly. Then the mixture can be set by raising and lowering the
mixture needles in the air valves. This should be done on an exhaust analyzer
following the instructions in the workshop manual. For everything to work
properly, the vacuum retard must also be working! This is so because with the
ignition retarded to 4 Degrees ATDC, the throttle opening screws on the
carburetors have to be screwed down way more to in effect "speed up the idle"
. with everything set properly, if the retard is not working, the timing will
be around 20 degrees BTDC and the engine will idle at 1500 rpm or so.
Sorry, I am sure this is not the answer you wanted to hear!.
It is might be possible to make things work without the retard applied,
but everything else needs to be perfect, and the throttle by-pass valves on
the carburetors will probably have to be modified to prevent them from opening
and bleeding air around the throttle plates causing the idle to raise up even
higher.
Regards,
Greg Solow
The Engine Room
Sports Car Specialists
Santa Cruz, Calif. 95060
831 429-1800
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