Holley 770 Questions

[Moritz55]

Hi Matt ... I have a 770cfm Holley on a Roush 427SR (even though the valve cover is 427R !!).. my Carb is identical to yours.. 2 mixture screws in the front (passenger & driver side) .. none in back... That's Normal.. nothing to worry about.

Note .. I have a solid rod linkage so my pedal moves precisely when the carb accelerator moves.. The suggestion to ensure your Return Spring is Stiff Enough to always return the carb accelerator is a geat suggestion.

Additionally as several already mentioned if you have a Mechanical Advance clean the springs and levers. I just replaced my MSD Disty Cap & Rotor as they were in terrible shape. 21k+ miles on them and never replaced by the prior owner! In the process I cleaned the Mechanical Vacuum springs/arms under the Disty Cap as a preventative measure ....

Good luck and hang in there..

[jhv48]

I see you’re in Florida so corrosion in the distributor is a good possibility.
My Roush 427sr exhibited similar symptoms. I tried the heavier spring, lower idle speed, disconnected the choke and cleaned and adjusted the distributor. Didn’t fix it. Finally got rid of the problem by replacing the entire carb base plate. That did it.
And if you want to get rid of that bog, consider a nice 750cfm with mechanical secondaries. I swapped mine and it woke up the engine. Vacuum secondary carbs are not the best choice for our light cars. Even the Holley website will not recommend a vacuum secondary carb for a light car.