gbauer, With your carb troubles, I checked again what is in my 390 Holley. Its a List 6390, a 4150 so it has both metering blocks. But the primaries would be the same. Not sure about the air bleeds as I don't know your List #### or what your bleeds measure.
I ran shootouts with my 390 Holley, stock 250, powerglide 3.08, both Clifford and Offy intakes. To get a good 60ft I would just STOMP on the 390 right at the line. If I hit a bad patch it would spin the right rear a little, no hesitation at all. Secondary opened up nearly all the way, and this carb won several of the carb/intake shootouts. It is well set up for sure:
Pri #51 main jets Pri .028" PVCR (hole sizes in the metering block, you gotta know those!) Power valve 6.5 or 8.5 not sure, that doesn't make much diff. Squirters are .028 yup that's plenty for the stock cam. You know the squirters have NOTHING to do with your full throttle or cruise mixture - they only operate like a squirt gun (actually like a mechanical fuel injection assist) while you are mashing the pedal. With the pedal in a steady position, the squirters do nothing at all.
Sec #52 main jets Sec .031 PVCR That is about equal to a 4160 plate with a .056 hole, a #3 plate has that size hole. Drilling them isn't quite the same but would be close. Sec spring was either yellow or purple one.
If you can set your carb like this its gotta be close, except again I don't know how the air bleeds compare.
Timing was about 12 initial, 32-34 total at 3000-3500, somewhere in there. Total timing cruising including vac was maybe 40-45 degrees, much more than that it will surge & buck as you describe.
Hope that helps, if not I'd try a different carb, you need a spare anyway!
I ran lots of carbs on that little 250: Autolite 4100s (440 and 500cfm), Autolite 4300 (440cfm), Carter 625cfm, Edelbrock 600cfm, Rochester 4GC 470cfm, Holley 390 and 450cfm. IIRC I even tried a Holley 600 on it, too big but it would run and cruise down the road ok. I rejetted some of them for the shootout but they would all run and drive right out of the boxes, not the kind of trouble you are having.
How do I know what metering block I have?
Here's Some pics:
I have no idea what size main jets I have so I'll just replace those too.
I plan on going down to the #28 squirter. I have a good #28 and a good #35. both with tubes and brand new Holley parts.
Power valve is NOT broken and it looks like I did the vac test wrong: I connected it to the lower vac connection on the carb by disconnecting the trans vac line. (auto trans)
I don't know if that would have made a difference or not though. I can't start the car right now because a) the carb is in pieces, and b) it's loud and I don't want to wake up my kids.
If the sizing can be done with the reading I have then the power size should be 10.5. From the research I just did online 1) the metering block doesn't match up with squat and 2) if I were to guess I'd say the jet should be a #52. Should I change the metering block out or what?
But, the real question is: would any of that cause the problems I'm having?
