Re: 4.0 head conversion with carb...whos done it?
Have you checked for vacuum leaks. I did the 4.0 head conversion last month and ran into similar problems. After ironing out the computer nightmare with the "nutter bypass" I found I could only get the motor to pop off for a second or two. It turns out I had a massive intake manifold vacuum leak and wasn't producing enough vacuum at idle. I had to retorque the manifold bolts in a three part circular pattern to get it to seal. I am currently running a Clifford intake with an edelbrock 500 cfm 4bbl. It runs great. I have also tried the Holley 2300 and a motorcraft 2100 that I had laying around. I have found that the 4bbl works the best. I was told by Clifford that the head breathes much better than stock and really needs a 500 cfm carb. Perhaps they were trying to sell a carb but it seems to work really well.
By the way. I was told by the boys at Clifford performance that the recently dynoed a 258 bored .30 over with their intake and header, stock ignition and an Edelbrock 500 cfm carb. They said it made 224hp and 290 ftlb of torque. I don't know what mine makes but it will set you back in your seat now.
'84 CJ7 258 .30 over,4.0 head (lots of fun head work done), Clifford intake & header, edelbrock 500cfm, MSD6A, Team Rush Ignition upgrade. Etc, Etc.