I recently installed a new Performer 750 and Performer intake on my '79 4-speed WS-6. The engine is mildly modified with a 068 cam, headers with 2 1/4 in duals, 6X-4's cut .020 for about 8.4:1, and a HyperTech cap & coil on an otherwise stock distributor. Rear end has 3.23's. The engine stumbles coming off the line between idle & 1200 rpm. The idle is set at 750. If I use hardly any throttle it has enough torque to pull and accelerate slowly and smoothly, and if I take off fairly quickly and slip the clutch or let it turn the tires slightly it is also smooth. I used the tuning instructions in the Edelbrock manual that came with the carb. Using various combinations of step-up springs, pump shot and rod changes(no jets yet) I've seen a small improvement. I also have tried initial timing changes, starting at 12deg, then 14 and currently 16. This did not seem to make any improvement. I pulled the cap & rotor to check the springs and weights for freedom of movement and they are ok. I was told once that the number on the vacuum advance canister is the total advance-is this true? It has 30 on it in two different places. I'm thinking that my problem may be advance related. If the springs are too strong would this be noticeable at such a low RPM with my combo? Am I on the right track chasing this problem? What should my total timing be? Also
how smooth of an idle should a 068 cam have with 1.5 rockers? Any advice would be great!

I recently installed a new Performer 750 and Performer intake on my '79 4-speed WS-6. The engine is mildly modified with a 068 cam, headers with 2 1/4 in duals, 6X-4's cut .020 for about 8.4:1, and a HyperTech cap & coil on an otherwise stock distributor. Rear end has 3.23's. The engine stumbles coming off the line between idle & 1200 rpm. The idle is set at 750. If I use hardly any throttle it has enough torque to pull and accelerate slowly and smoothly, and if I take off fairly quickly and slip the clutch or let it turn the tires slightly it is also smooth. I used the tuning instructions in the Edelbrock manual that came with the carb. Using various combinations of step-up springs, pump shot and rod changes(no jets yet) I've seen a small improvement. I also have tried initial timing changes, starting at 12deg, then 14 and currently 16. This did not seem to make any improvement. I pulled the cap & rotor to check the springs and weights for freedom of movement and they are ok. I was told once that the number on the vacuum advance canister is the total advance-is this true? It has 30 on it in two different places. I'm thinking that my problem may be advance related. If the springs are too strong would this be noticeable at such a low RPM with my combo? Am I on the right track chasing this problem? What should my total timing be? Also
how smooth of an idle should a 068 cam have with 1.5 rockers? Any advice would be great!

I had this same problem and I dont know if it is the same as yours but its something to check into. Mine would drive fine during regular driving or mild aggressive driving but if I really got on it it would fall on its face till about 1500 RPM's. Simple solution was, the choke was getting only like 9 volts and when I had floored it after it warmed up, it sucked the choke closed. Check that before you do anything else. I have only had this problem on my edelbrock

I had to get a manual choke 750 to use the shaker and at the moment it's safety wired open until I can fabricate a cable mounting bracket. Good thing spring comes early in Tennessee!