Carbs: Two Holley #9776, 450 CFM, manual secondary NOT double-pumper. (These use a secondary metering plate with manual butterflies, not a vacuum dashpot.)
Heads: Large valves, open chambers, Ram Air IV intake ports, ported, gasket matched, 3-angle valve job. (455 = #7K3 & 428 = #64)
Presently on my 455, I run the two carbs BACKWARDS. Sounds strange, but it works great - and it was the only way to clear the waterneck with a pair of Holley cabs. I made my own custom linkage that moved the throttle action to the passenger side of the engine and operated the carbs in reverse. They are not progressive from carb to carb. As soon as I put my foot into it, I am running on 4 Barrels. No wonder I only get 8 MPG.
A duplicate of this 455 set-up will go onto my 428.
My "new" 455 set-up will be two of the same Holley 9776 carbs, converted to double-pumpers, oriented face-to-face. To accomplish this, I have moved the two carbs to the rear by about 1/4 inch and come up with another set of custom linkage that operates the two carbs in synch. I also shaved about 1/8 inch from the fuel bowls of each carb. Half of that shave was the "Holley" logo!
I have been toying with the idea of trying out an Edelbrock P-65, but more than one source have mentioned that the Offy is a superior manifold. I would like to try Dual Q-Jets on the P-65, as I have already set up my 3rd Offy to run this way. (Dual Chevy Q-Jets face to face, slightly skewed so that the fuel inlets don't bump ...)
The performance from my 455 with the dual Holleys is incredible. I recently switched from #670 heads to #7K3 heads. After getting the jetting almost right (I still have some tweaking to do on the secondary side), I can hardly feel a difference, even though I dropped the compression by 2 points. There is so much throttle response with this set-up.
I have never tried Carter or Edelbrock-style AFB carbs. I owned a Mopar once, and that was enough to keep me in the GM family forever.
