This Sucks!

[jasonsevilclone]

All right here's one for the pro's. I have a 66 coronet with a 318 poly. I just swapped out a distributor equipped with an igniter II module in favor of a 73 Charger unit with a magnetic pick up and used a mallory hy-fire module instead of the stock control module. I got it timed and everything was cool until I reconnected the vacuum advance. It idles fine at 10 BTDC but as soon as I step on the gas it advances too far and begins to sputter and backfire. I figured I would take the advance out of the old distributor when lo and behold it was never connected to the advance plate to begin with. I have a stromburg? 2bbl carb and it is connected by a vaccum line directly to the vacuum advance. Should there be some kind of diaphragm or module in between these two? Going over the vehicles records I see that the carb was rebuilt about 18 months ago and I think I smell a rat. Did the guys who rebuilt the carb disconnect the plate bacause they had the same problem I'm having? Any help or information would be a great help. Thank You, Jason.

[JVMopar]

You've got the vacuum hooked up to the wrong port. It needs to be hooked up to ported vacuum, and I'm assuming that you have it hooked to venturi vacuum. The difference is that Ported vacuum is greatest when the engine is cruising or at steady state, not at idle and not while accelerating.

So the vacuum advance is coming in at the wrong time. Get a vacuum gauge and check it out.

[jasonsevilclone]

i think I got it right. When I reconnect the vacuum advance at idle it still runs fine but as soon as I stab the pedal Kapoww. The number stamped on the advance reads 9.5 is this creating too much advance or is this about right?

[c318cuin]

With 0 initial advance set to 0 that gives you 19 degrees total. So in theory you could set inital timing to 11 degrees and end up with 30 degrees total. Which should be safe too. I bet either like JVMopar said "vacuum hooked up to the wrong port" or the carb may be messed up.

Good Luck

[6 packin]

The advance plate does not relate in that way to the vacum advance! The plate stamping is refering the the slots for mechanical advance. I would ditch the vacum advance altogther if I were you. I found them usless for engine with good perofrmace advance curves like 10 deg intial or more and 30 total and more. Maybe for a stock grocery getter there ok! If you look at your High dollar aftermarket dist they have no vacum advance only mechanical.

[skankweirdall]

If my memory is correct (it ain't been that good lately) the initial advance on those engines was 0 or a little ATDC, or there abouts.
I might be wrong though, try and find an old tune up manual or Chiltons manual.

[jasonsevilclone]

Sir 6 packin, I took your advice and capped the vacuum advance. I took it out for a test drive and whoom. I was flyin'. I'm thinking my old setup must have been seriously wack because now my ride is hauling ass. Thanks for the advice. If your ever in San Francisco stop by, I owe you a beer.

[6 packin]

Never been that far out! I have been to Sac a few times though.
Thanks for the offer.

Happy motoring!