LURK_MODE=OFF
SOL mates!
OK, here's the background:
BMC B series engine with shallow dish pistons, modified head at 9.75:1, 270
Piper cam, twin HS6 with K&N filters, Maniflow LCB, Hitachi electronic
distributor. The power plant has about 2000 miles on it and I've been fine
tuning it all that time. It now makes excellent HP, excellent MPG, about 30
mi/imperial gallon but it simply will not stop running-on when shut off!
The plugs are perfect tan colour, it's not over heating at all even with a
195 F thermostat (max temps around here are in the low teens C), it's not
over advancing anywhere in the range and there's certainly no carbon
buildup in the chambers yet.
I've tried going from BP5ES to BP6ES plugs with no improvement although the
colder 6's show darker brown around the body so I switched back. Leaning
the carbs off a couple of flats initiates lean surge at highway speed, a
couple of flats more fuel colour the plugs too dark so I figure I'm THERE
with the mixture. I recurved the dizzy to give me more advance all through
the range (I have a SUN machine :-) which greatly improved the part
throttle manifold vacuum and still showed no sign of over advance, but
changed nothing on shut-off. Right now I've got an initial timing of 10
BTDC and it maxes out at 35 BTDC at 4000 RPM. It hauls butt!
Obviously something in the combustion chamber is over heated causing it to
diesel, but it's not the plugs, it's not carbon and I paid particular
attention to eliminating sharp corners in there when I built it.
Anybody got any other ideas on what I can try?
--Marcel Chichak chichm@planet.eon.net
Edmonton Alberta Canada, eh?
Peek into my world: www.planet.eon.net/~chichm
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