Ah! I let this thread go, I haven't been able to get on in a while here.

I set my initial to 8 degrees, and we're still having the same problems here. I have really steady vacuum, about 17" at idle.

I'm starting to think it's a valvetrain problem. I want to go through and totally readjust all the valves and see if it helps at all. There is a tick on #5 intake, and I don't know if it's a lifter or a loose rocker arm. I was trying to hot adjust it, and gave it about a 1/4 turn tighter, and the motor seemed to lug a little, so I backed it off, not wanting to do any damage inadvenrtantly.

Both of these distributors were new, one brand new (the Accell Blueprint Points-style) and a newish HEI with an Accell SuperCap. The HEI was in use on the last motor, and worked like a dream.

Also, it should be noted that only the 750 is a double pumper, the first 600CFM was an edelbrock, and the 650 was a Holley, non double-pumper.

I'm leaning towards valve adjustment thought. Thanks alot for the help, You can probably imagine how frustrating it is to have a brand new motor, and and endless supply of problems. Sigh. Hopefully this thing will run right someday