Neil,
Don't over look a more effecient exhaust system will cause
the engine to run LEANER, which may affect the cooling.
If the system was on the borderline of overheating, changing
the exhaust system may be enough to suddenly have the borderline
condition become very noticeable.
Years back, on my 67 2000, I ended up making a little O2 sensor
to check the exhaust emission. With the roadster, and SU's,
they just like to run rich. Never could find a problem, but
around 3500 rpm it would hesitate and loose power. With my
"on board" sensor (heated O2 sensor, and a sensitive volt
meter) I was able to confirm it was running lean around 3500
rpm. Changed the needles and seats... and despite using the
"same" needles, the new ones worked wonders. Seems the old
needles had a "milky film" on them. Really odd, no idea what
happened... but difference was noticeable.
MIKE -- When you set your timing, ALWAYS CHECK the total
advance. Disconnect the vacuum line, and rev the engine up
to a good 4000 rpm. You shouldn't go beyond 30 degrees of
timing. With the '68-70 models being set to 0 BTDC, it is
all too common to find a "late" distributor in a 65-67.5
roadster timed to the wrong place. Overheating, pinging,
and possible engine damage as a result.
Cheers,
Tom Walter
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