Tym,
I can appreciate your frustration. But, it's important at this stage that
you only make one change at a time, otherwise you have no chance to diagnose
the problem, or worse, you will create a new problem. Chris has asked some
of the pertinent questions. To those I would add, what happened after
putting in the 190 thermostat and before it acted like the plugs were
fouled? Did the engine ever run strong? At this point, if the plugs are
clean - that's what you mean by "fine"? - then the symptoms sound like it is
running too lean. It's possible that the fouling was from oil consumption
while the rings were seating and now that's OK. BTW, what intake manifold
are you using? As for the carb, I certainly agree with Chris that 750 is too
big, but that shouldn't cause the problems you describe. What size jets are
you using? This carb comes with 70's in front and 76's back. These should be
plenty rich, but could possibly be too lean depending on all the factors
involved. A bigger cfm carb needs bigger jets because the flow velocity is
lower, but I think the stock jets are a good starting point.
Maybe the carb isn't the problem; it might be an ignition problem too. Pull
a plug wire and check to see if it gives a strong spark to ground. (Be
careful !) If the spark isn't real strong, then maybe there is an
incompatibility issue; for example, does the MSD coil use a ballast resistor
and if so, what resistance. Different coils have different impedances. If
the spark looks good, use a timing light to see how the timing varies from
idle to max advance. You should have roughly 35 degrees total advance and it
should be all in by 2500-3000 rpm. Where it starts at idle is not so
important, but around 10-15 degrees initial would be good. All of this will
need to be revisited and fine-tuned once you get the main problem solved.
Hopefully, by now you've found the problem and now you're happily motoring
around town.
Good luck,
Bob
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