need help tuning my CJ

[srh11293]

This is my first post on this forum, and I hope someone can help with ideas.

First of all, about my CJ. It's a 1984 CJ7 with Clifford Performance engine set up (previous owner did all of the engine modifications), and a holley 4412 carb. 4 spd T176, stock axles, hedman hedders, 4 inch lift.

The CJ7 backfires under load. Can't seem to resolve this issue.

Details: Timing was set to 8 degrees BTDC. Holley was completely rebuild with 74 main jets, 50 ml accelerator pump, 6.5" Power Valve. The engine idles @ about 700 rpm with 17 psi of vacuum (sometimes gets to 18. Mixture screws are set to about 1 1/4 turns out.

Since 258 (even build ones) don't put out that much power, should the main jets be reduced?

It's not running rough, no black smoke, no dieselling - so it does not seem to run rich.

Maybe it's running too lean, but with that Holley I have a hard time believing that.

No, I did not check my spark plugs yet - did not run the Jeep long enough - only about a mile total - finishing up the 'build' phase.

I also have a Weber 32/36 that I can install (also need to figure out the correct jets and other parts on that carb) - but it'll require different adapter plate, different throttle cable hook up, ... so for now, would like to stick to the Holley.

Any suggestions on what to check for would be highly appreciated.

Thanks,

Vlad

 

[Empty Pockets]

I am not sure if the jets correspond to one another, but on my Motorcraft 2100 sitting atop a .030 over 304, I use 45 jets at high altitude and 46 or 48 jets at 1,000ft. The 2100 is 287CFM with 1.08 venturi, the Holley 4412 is between 500 and 599 depending on how it is set up. Even with the 46 jets, I tend to run a bit rich at low altitude. Sounds like you are way over carburated unless there have been some extensive engine mods. I'm not sure what "Clifford Performance" set up all entails, but IMHO it would have to be pretty radical to use that much CFM properly.

 

[superj]

i think its the intake manifold, exhaust manifold, and filter assembly.

 

[k-2]

backfire under load - I would start with ign - secondary side - coil, plugs, wires -


Choke engine a little and see if the richer setting changes the issue,