Dane Trask

I have two edelbrock carbs both in like new condition; 600cfm electric choke, 750cfm manual choke. I think my need is right in the middle. I have time on a tuning dyno next Tuesday, I have rejet kits for both, so which one do I tune, the 600cfm tuned up or the 750 tuned down?

I have a 1979 360 with a mild cam 284/484, J heads with 2.08 valves, hooker headers, Weiand stealth intake, upgraded distributor and super stock Accell coil, A-727 with 2500 stall converter, 3.55:1 rear gear.

Coronet 500

750 for sure, if you have the valve train for rpm you won't be tuning down much if at all.

Iowan

I'd go with the 750, my 292 Ford makes 8 hp more with a 750 than a 600 Holley.☺

ZEN357

600 cfm and tune up. You be better off with the electric choke for street driving.

RacerHog

750 or 780 would be for me....
Hope you raised the compression a tad?

Dane Trask

DYNO DAY!!!
I have 3 hours on the Dyno to tune both the 750 and 600. I am pumped. Yesterday I freshened up the ignition system and took care of a miss that was happening at low rpm, (I think the air gap was set too tight and one star on the reluctor was touching the pick-up. I am going to attempt to video a bunch, regardless I will post results.

Drag Pak

I wouldn't waste the time on the 600. My 340/357 ran/dyno'd great with the same cam, 2.02 intake valves and a six pak.

Iowan

I would guess 10 hp. deference between the two if both are tuned correctly.

Dane Trask

Iowan is closest!!
The winner is! EITHER!

These are the best runs:
750 one stage lean (rod only) orange springs: 260.3(hp)@5350(rpm), 312.4 (lb-ft)@3000(rpm), AFR=11.5, duration 8.324sec
600 three stages rich (rod) two stages secondary (jet) orange springs: 256.8(hp)@5650(rpm), 314.4 (lb-ft)@2900(rpm), AFR=12.5, duration 8.373sec

The two can be tuned to almost match max hp and tq, the deciding factor really comes down to taste. The 750 is louder, thirstier, and a rougher idle, but it has better top end. The 600 is much nicer on the street, smoother idle and snappier, the torque comes in earlier, but the top end is breaking up a little (I think I can go to three stages on the secondary's and run 93 to clean that up). For me the deciding factor is the smoother idle and the electric choke on the 600. Hope this helps someone else in their decision. below are the important runs. I did 14 in total, but some were stupid timing and accelerator pump location adjustments.

750 silver springs: 249.9(hp)@5250(rpm), 300.7 (lb-ft)@3750(rpm), AFR=11.7, duration 9.241sec
750 one stage lean (rod only) pink springs: 257.9(hp)@5400(rpm), 311.7 (lb-ft)@3100(rpm), AFR=12.1, duration 8.758sec
750 one stage lean (rod only) orange springs: 260.3(hp)@5350(rpm), 312.4 (lb-ft)@3000(rpm), AFR=11.5, duration 8.324sec

600 stock Orange Springs: 250.3(hp)@5300(rpm), 309.9 (lb-ft)@3100(rpm), AFR=12.9, duration 8.072sec
600 one and half stage rich (rod only) orange springs: 249.3(hp)@5500(rpm), 312.0 (lb-ft)@2850(rpm), AFR=12.8, duration 7.907sec
600 three stages rich (rod) two stages secondary (jet) orange springs: 256.8(hp)@5650(rpm), 314.4 (lb-ft)@2900(rpm), AFR=12.5, duration 8.373sec
600 three stages rich (rod) two stages secondary (jet), orange springs: 245.4(hp)@4900(rpm), 311.4 (lb-ft)@3050(rpm), AFR=13.0, duration 8.254sec AIR CLEANER

Iowan

On my 292 cid W Ford, 455hp with 750 and 448hp with the 600.

RacerHog

I would not have guessed the AFR would have been that close ether?
I wounder what it would look like with California Blend Fuel..