I did a 2bbl to 4bbl swap. Now I have a miss at ldle. I also had some popping through the carb when I pulled it open and let it off. Figured it was either timing or running lein. Timing was confusing since I have a 69 350 with a 67 timing tab. assuming it is placed correctly it is timed at 12* @ 850 rpm idle. That took almost all the coughing out. It did do it once more when I test drove it and goosed it in park. Book says it should be @ 8*. I noticed that when I replaced the vacuum advance there was no change. I plugged and unplugged it several time and saw no change. The carb is pulling vacuum. On the test drive the car is ******* it in the low rpms but strong from 40 mph and above. So is it a vacuum issue timing or what? Any thoughts?

 

If your vacuum advance is connected to ported vacuum(no vacuum at idle), you will not have any advance at idle. Make sure all your wires are firmly snapped in place at the cap and spark plugs. What distributor are you running?

 

I put in new plugs checked the gap, new plug wires, checked the connections twice. It's a stock distributer near as I can tell. Vacuum advance is connected to the vacuum on the carb.

 

Are your points good, is your dwell set to 30?

 

Check and re-check the firing order. Which distributor cap did you use, the old one which was known to be good or a different one? Minute carbon tracking inside the cap, looks a like a pencil mark/line and is very hard to see, can cause this. Good luck!

 

How did you determine that the carb is pulling vacuum? You should definitely notice an increase in RPM when you hook the vac adv back on to the carb. Is the port on the carb blocked off when you set the timing?

 

Did you say the pot your vacuum advance is connected to has vacuum at idle?

 

i will have to check the dwell, cap etc. just pulled the distributer then reinstalled it. didn't mess with it during the swap so figured it was still ok. timing was set with the vacuum advance off and vacuum plugged. i can feel the carb sucking vacuum when i put my finger over the vacuum tube. but when i attach and unattached the vacuum advance there is no change and it seems there should be. I did notice that the intake bolts torque specs in my edelbrach instructions called for 25 ft # and the service manual says 35. I thought that difference may have been due to the aluminum intake being softer. maybe I'm not tightened down enough and leaking. i don't want to over tighten it though.

 

If you have your advance connected to a port with vacuum and your not getting any increase in timing, then yes, there is a problem. May be vacuum advance can or advance plate.

 

Put the vacuum hose to the distributor in a vacuum pump, or your mouth and pull vacuum, or suck on it. Does it hold vacuum? If it doesn't, your vacuum canister is bad and needs replaced.

 

Check the centrifugal advance weights, they should move easily.