motor in sig...I set intial timing to 16* where I had it last time I built the motor which put it at about 32* total. Problem is it would have trouble starting when hot. Had to back it down to about 13* to get it to fire up real crisp everytime. But now when I shut it off it diesels a bit. Its just under 1k in park and about 820 or so in drive. If I lower idle rpm it has a hard time staying alive while in drive, so I have to keep it where its at because of cam (FTI cam ~.600 lift).

What Ill try is to get rpms up with idle mixture screw so I can lower butterflys a bit more then maybe it wont diesel? Then adjust my mechanical advance back up to 32-34 total?

 

I am not the best at adjusting carbs, so take my advice with a grain of salt. First, I have a few questions.

Is there fuel dripping of the venturi at idle?
Is the idle stop screw set to hold the butterflies open a bit at idle?
Was the idle set attempting to get the most vacuum?

 

fuel dripping off venturi...uh dunno

I set the idle mixture screws to give me highest rpms..which gives highest vaccum...then adjust butterflies to give idle i wanted.

 

Somebody help me out here. I've wondered about this for years.

How can timing affect run-on? When you turn the key off, the spark quits, regardless of where the timing is set.

My experience is that run-on (dieseling) is usually caused by hot-spots on the piston or combustion chamber, plus throttle plates not fully closing and fuel still getting in.

 

An overly rich condition can leave fuel on the floor of the intake.

EZ, take the air filter off and with the engine running look at the venturi. There should be a fog. If the carb isn't adjusted correctly you may see drops of fuel coming off the venturi. This will cause an overly rich condition, see links.

http://forums.holley.com/entry.php?4...n-Holley-Carbs

http://en.wikipedia.org/wiki/Dieseling

As far as the timing question---

It would depend on the distributor where I set the base timing. I like to set timing at 3000rpm and see where it falls out at idle. Again, it depends on the distributor. Sometimes it may need to be recurved to be optimum at both idle and all in.

 

This is the approach I've always used, set the timing at full advance and let it fall where it will at idle.

 

usually you can rev to about 3000, advance till the engine starts to break up then turn back a degree or two. I do it this way then check with a light to see where its at.