I am running a 650 doublepumper now but I just can't seem to get my primary's right. Need more shot but when I increase my jet size it loads up. If I invert the plastic cam I get better accceleration, but a little stumble. There seems to be no happy medium. Maybe I need to buy the cam kit?
Yes i think you need to play with excellorator pump cams. I had an 800 dp on a 390 played with the cams never had a stumble could idle out in 1 gear stomp it and it would go of corse it was a 4 speed with a 486 in it.
I down sized the primary squirters from 28 to 25 and changed the cam to one from the barry grant kit. Seems to be alot better almost no stutter. I saw the gas dribbling out of the squirters on a slow acceleration, went back to my holley book. It said to try to downsize the squirter or change the pump diaphragm to a 50 cc. Now to work on the secondaries. How big can I go? Have 70's now 76?