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Join Date: Oct 2007
Posts: 1,582
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Quote:
Originally Posted by Aurel View Post
Car is 1978SC.

I am assuming my mixture is too lean because I never readjusted it after switching from 8.5 to 9.3:1 compression, backdated exhaust and sport muffler.
It runs fine but has a few symptoms below:

- Cold starts are difficult, usually starts on 4 or 5 cylinders, then backfires and then runs on all cylinders just fine.
- If colder, I usually have to lift the pressure plate to get it started.
- If I set the idle air bypass screw to be 950rpm when hot, it oscillates when cold.
- Backfires a little bit on deceleration
- Spark plugs are light grey, very clean.

So my plan is to richen the mixture a tiny bit. Other suggestions?
You can raise the plate ever so slightly and judge to lean or rich. I think if you move your lever up just a tad and the RPM increases you are too lean.


Or here

911 CIS Primer - Testing:

Although this is based on 14.7 AFR? Nothing beats the AFR meter.

Mixtures
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Old 05-15-2023, 09:39 AM
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