Distributor curving.

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Hey Tom. Not sure if your still with the car this evening, but try and hook the vac. adv. hose to manifold vac. You'll have to lower the idle back down afterwards and i'd reset the idle mixture screws also. Give it a test drive and see how she is. I have a theory on this, but don't have time right this minute to type it all out. I'll get back as soon as i can.


Rick
 

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This is my friends car mine is doing great. Good to here from you again. I will try that tomorrow also Im gonna hang a used advance unit on it after I try you thing.
 
The more i look at this, i may be off base here. My thinking was that it's unburned fuel making it's way to the exhaust. With the vac. adv. hooked to ported vac. you lose that advance as soon as the throttle is closed and then the mixture is burned later in the cycle allowing it to be closer to the exhaust. The fly in the ointment is this is not happening with the vac. advance unhooked, which simulates no vacuum on deceleration. My theory was that with manifold vacuum, you still have the extra advance during deceleration and would burn the fuel before it got to the exhaust. Since this just occured with the recurve on this dizzy, it could be something completely different. If by chance the manifold vac. cured the popping, the initial timing may have to be backed off several degrees to run the manifold vac. and not be over advanced in a normal cruise situation. Hope my thinking made sense to y'all, if not, let the beatings begin...lol. :violent1:.
 
I had a idea also that the idle circuit could be too rich or lean on decel, so i reread the thread and saw that Bill had made mention of it.

BillGrissom said:
Popping thru the exhaust when decelerating is common. Many motorcycle carbs have a bolt on part (forgot name) that adds fuel under high manifold vacuum (decel) so it doesn't pop, which suggests it is from "too lean" misfire, putting unburned mixture into the exhaust. Many remove them, to save fuel or because they like that popping sound. I suspect if you don't totally let off the throttle in a low gear, it won't happen.
Click to expand...

You may try some minor tweaks to the mixture screws and see if anything changes? Easy enough to try. I have my way of adjusting them on 2 corner metering block style holley's that's different then 99% of the members here, so i'm a little hesitant to even speak of it. And no, a vacuum gauge or tach is not involved :D.
 
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