Another backfiring (make that Afterfiring!) V6 post...

Searched and read through pages of good comments and ideas regarding subject but none fit my issue. 225 V6 with HEI conversion, and stock 2G carb with headers pops and after fires Backfires is a misnomer - mine is afterfiring from exhaust) '

First, it does'nt like to idle at stoplights very well. I have to run just a tiny fraction of choke to make it run smooth...

Afterfiring is primarily from right side dual exhaust on downshift, but it gets a really good POP or two in there at idle too.

I've timed, re-timed, triplechecked plug wire placement, spent hours with an idle setting tool trying to get mixture corrrect...

should next step be vacuum gauge and attack idle again?

 

Sounds like a vacuum leak or restriction in idle circuit if you have to run the choke on slightly.

 

x2 above and possibly water in fuel.

 

I had the same trouble. It was trash in one of the ports on the idle circuit. Also, if you've had the carb apart, there are several different style gaskets that go between the venturi cluster and the body

 

Is your HEI a new conversion? It can be off.not by firing order but by plement on the cap, mine was and caused that problem on the right side #6 cyl.

 

Did you grind off a spot on your intake manifold for the HEI to fit? If you didn't, it probably isn't seated all the way down. If you did, did you grind too deep and get a hole sucking air?
I did the conversion on mine awhile back and that is one thing that you have to be careful with.

 

http://www.jeepster.org/swchapter/hei-2.html

heres some good info.

 

I ordered a HEI distributor from Napa for a 225 V6 . After installing, it would backfire and run rough, but it was driveable. I did everything new wires, plugs, timed and retimed checked for vacum leaks. It turns out the distributor was for an even fire engine . The electrodes in the cap connecting to the spark plug wires are positioned differently among other things.
Got the oddfire distributor jeep runs great!!!