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Old 04-11-2010, 10:19 AM
red65mustang red65mustang is offline
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eric,
your motor and cam combo should be able to show 14-15Hg at idle at 800-900 rpms warmed up tuned correct...
(which is plenty good)

on the street a carb want/needs about/atleast 13Hg at idle to make a decent "atomized" spray that will stay in suspension with the air all the way into the cylinders so it will burn with such slow piston speed...

ex/illustration based on your first post:
(liquid gas does not burn)
with the present only 12Hg worth of atomization quality and a cold motor the idle sputters because some gas is condensing back to liquid by contacting the still cold intake runners...
(the carb gas spray droplets are too big {due to marginal HG} and probably too many droplets due to the too rich jets)
that's bad because that liquid gas is washing oil off the rings and cylinder walls and getting into the oil pan...

for right now till all gets sorted out,,,,raise the idle to 1000 (+?) and increase the base 2*'s,,,,"should" get you to atleast 13Hg...

the too rich jets are contributing to the low idle Hg but hard to judge how much,,,, and the black plugs are telling you it is too rich so correct the jets ASAP...

swap jets and post idle Hg with 16 base and 800

re:pcv
the factory engineered fuel feed curve (based on ever changing Hg present for how much gas is fed) is calibrated to include the air from the pcv to end up with a correct air/fuel ratio for any Hg condition...
pcv itself does only good things for a street driven motor,,,use it correctly for long motor life...

re: less plug gap
"recommended" oem gap is a "compromise" choice so a car can run anywhere on the planet regardless of altitude/temp/gas quality/etc...
what happens when you reduce the gap is there are more milli-amps in the actual spark which is the "heat" (aka "blue flame hot") that keeps plugs clean...
with a big plug gap the coil needs to constantly charge to a much higher KV to be able to jump the gap to first burn a hole thru the mix....
so then/next how ever many milli-amps are still left actually light the mix and clean the plug (aka just a yellow flame worth of heat)...

second benefit from less gap is the coil will last longer because it stays cooler,,, which also helps add milli-amps to the spark...

re: 24* idle timing
vacuum advance does nothing except good for a street motor...
more timing will raise Hg to make better/more power at street rpms...
set your base to 16 for long-trouble free batt/starter motor life and add 8* worth of vac adv hooked to a manifold port on the carb...

a inherent fault of any performance cam is less low street driving rpms TQ power output compared to a stock cam...
more timing does help!!!!

Last edited by red65mustang; 04-11-2010 at 10:25 AM.
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