rough idle with vac advance

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curts73

curts73

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hi guys i am having a problem with my 360 it runs fine other than hesitation on hard take offs. but when i hook up the vacuum advance it takes the gas great but at idle it pops through the exhaust and runs rough. can anybody tell me what could cause this because i have tried advancing and retarding the timing with no difference.i even tried a new distributor because i was still running the original 73 model. dont have the money right now for msd setup.
 
What vacume port do you have it pluged into? The one with vacume at idle or the one with out vacume at idle? It should be in the one with out any vacume at idle.
 
i have tried both ports and the timed port just makes it pop when i am on the gas even a little,just enough to open the vacuum port.
 
Something strange is going on......if you tried 2 different distributors, and it pops out of the exhaust.....and only with the vacuum advance hooked up.......and it doesn't matter if you advance or retard the timing? Naw, I'm thinking you may not be reading something right here. I'm almost wanting to say it's something in the carb or a vacuum leak.
 
Well now that I read it again you say it does it "at idle" with it pluged in. If you plug it into the port with no vacume at idle the vacue pot should be doing nothing. I don't know? Very strange. Did you mean off of idle? What idle RPM are you running?
 
did the car just start doing this or did something get changed on the motor recently? also how is the motor mechanically, such as timing chain, comp., is the balancer reading correct, etc. most times popping out the exhaust is the timing being way too late.
 
What distributor do you have? If it is a Mopar stocker the air gap in the pickup might be off. It will cause erratic firing when the pickup plate rotates.
 
i did a quick vacuum test and the gauge is reading a steady 20 inches of vacuum at 700 rpm idle,and 22 inches steady at about 2000 rpm. i tried a little test with starting fluid sprayed around the intake and carb base and i found a few spots on the intake that the engine reacted to and the back side of the carb also gave the same reaction.
 
If it miss fires at idle when you hook it to direct vaccum, and then does it when you accelerate on the time vaccum port, I would say your to far on the intial timing? But you'll need to adress the vac leaks first.
 
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