dwell question

[porsche930dude]

My 82 sc runs pretty good but its idle is very eratic. Sometimes it idles fine but most of time after racing it wont settle down it stays at 1200 rpm . sometimes it idles fine but rises up to 2k or so after idling for a bit. Almost all the time when starting hot it races at 2500 and very slowly settles down. Sometimes while cruising at a steady speed it feels a little studdery. Iv played around with things quite a bit. I have not checked the fuel pressures yet and i wil soon. The only real problem iv found sofar is that when the vacume retard and advance is disconnected and plugged the idle raises up quite a bit which prevents me from setting the timing with the lines disconnected. If the wur checks out i will pull the distributor apart and clean it up. I have attempted this once before but would not get far because one of the allen screws was stripped so i gave up.
Anyway on to my question I checked the dwell with it warm at the green wire on the test port and this is what i have. Pink is at idle and yellow is above 33% throttle. When going from idle to racing the neddle rises consistently to the yellow and thats where it lands. So does this indicate rich or lean? its suposed to be 35-45 degrees correct? The thing is i checked it with the pull the plunger down trick and i get a decrease in idle but no stalling or racing which would indicate perhaps a bit rich but not overly which is where it should be right? I should have checked the fuel psi before bringing this up but i couldnt help myself.

[porsche930dude]

Could it be because my meter is made by the devil I just noticed its model 666

[rattlsnak]

I'm not sure I follow you here. Dwell is a function of timing, not fuel, and has nothing to do with being rich or lean. Dwell is set on a 'points' based system. If your SC is stock, then it has electronic ignition and you have no way to adjust the dwell. Its all handled through the CDI box based on the trigger wheel inside the distributor. Now, if it is WAY off, it could cause problems, like skipping, missing, etc, which would give you a too rich/ too lean condition. But the point is, there is nothing you can do about it with an electronic system.

(dwell is actually the amount of time the points are closed on that type of system. i.e., if you need more dwell, you decrease the point gap, etc.)

[mca]

I think he is using the dwell meter in order to determine the frequency valve duty cycle - although the Lamda may be "running" ... it may not be running correctly.

This explains it better than I can:
Cold Start Issue - Video