Well, I talked to the engine builder today. I wish he were more of a carb guru but I like him anyway ... alot actually, he's really good at what he does.

Sorry if I express my frustration but I've been messing with this on and off for over a year. I don't mind learning but this has come very slowly. I probably will get a book now that I realize Holley carbs aren't setup to run on Mopars.

Talking to the builder, plus thinking about it on my own, also consulting "the Google," and as Fox has stated, it looks to be the idle mixture that is super lean. Other non-Mopar folks are dealing with the same issue on the Holley 750 on modern gas.

There are a few suggestions and I tried cranking up the idle mixture to test it out somewhat. Sure enough, that does appear to make a big difference. The plugs look a little better too. It still pings somewhat. Too bad I don't have a real 4150 carb where I can adjust the IAB without making lifelong changes to the carb. It also looks like a bigger idle well in the carb makes a difference too so I think I'll see if I can find one of those.

My biggest problem is before the power valve comes into play. I can certainly fix this somewhat with a power valve with a higher number but that isn't the only thing not working here.

Also, I'm having problems under steady load, not under changes. The accelerator pump is working quite well. I'm having trouble on very slight grades where I get into the throttle just a touch and then have to hold it there.

I picked up a Quick Fuel primary block yesterday. I took out the 0.028 idle fuel restriction and installed the 0.031 that was in the package. I think I could handle an 0.035. This cleaned up things considerably. I still have ping under steady light load but it is much more subtle and harder to get it to do.