>First, the 10 degrees BTDC timing does not seem to work well. Way too
>retarded still. Seems to contribute to motor overheating. The cam is a >270
>duration. CR is 9.6 to 1. Should I be using a different timing on such a
>cam? How do I determine correct timing ?
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Retarded timming will definitely cause overheating, but 10 degrees advance,
is in the ball-park (should probably be around 12 deg). Too much advance
will not cause overheating but will cause detonation! Use the old -
fashoned way of advancing timing by setting the advance a few degrees at a
time until you hear it start pinging under load, the back it off a few
degrees. The engine will now be timed close to optimum for your
configuration. Secondly, over rich mixture will not cause overheating,
over-lean mixtures will. Over rich mixtures actually run cooler from the
cooling effect of the dense cool mixture hitting the cylinder walls.
Your overheating problem sounds like your not getting proper air/water flow
at speed. I personally suspect its water flow, and might actually be
flowing through too fast, not staying in the radiator long enough to
transfer the heat away from the engine before returning. Could also be the
reverse (had the same problem in another car found the water pump impeller
had disintegrated causing the very same symptoms you describe) Cooling
problems can be a real pain, I still haven't figured out why my GT6
overheats at idle, hope you solve it - let me know what you find out!
Barry Schwartz
Bschwartz@encad.com
Bschwart@pacbell.net
63' Spitfire, 72'-V6 Spitfire 70'GT6+
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