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Re: [T3] Backfiring at 2000 RPM and higher

GaryT=> the sound is accompanied by a
=> puff of blackish smoke

OK, for starters, it's not a problem with a cutoff jet or your points, so
don't waste time chasing your tail there.  It's most likely this is a timing
problem (ignition advance, valves or carb sync), or possibly an exhaust
leak. That black you see is soot and unburned fuel.

You imply that this began when you were working on the distributor, so we
can start there. Dwell should be in the 45-55 range; start with a point gap
of .016". While you're in there check that the breaker plate is well seated
and not floating around. You might consider putting a stock distributor on
your shopping list; the 009 will get you by for the time being, but it's
crummy for this application.

Now check the inside of your cap for black streaks that can indicate a bad
spark path, put it back on and doublecheck that your plug wires are going to
the correct cylinders. Doublecheck that your distributor is fully seated in
the case, with no gap at the shoulder.

Set the 009 for 7.5 degrees advance at idle if you're at around sea level.
Your ballpark description of your current advance leads me to infer that you
may not be real confident of how to set or check advance. Precision matters
here. You'll want to get hold of a good manual if you don't have one and
learn this procedure for your car and especially your specific pulley --
sometimes they get changed.

If all that checks out, recheck your valve lash all around.

No problems so far? Look for an exhaust leak. You might be hearing it at
idle and not realizing it. The postignition that you describe would continue
intermittently in all rpm ranges once the engine's warmed up.

Next step: carb sync and that whole can of worms.

Steven Ayres, Prescott AZ
'66 KG1600

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