Setup for 750DP on this 408

Mattax said
Tuning for Performance.
This requires systematic trial and error to improve performance. Performance defined as power, torque and engine efficiency.

Start at the idle and work up.
Idle and off idle are your foundations. If its crappy at idle then the engine is going to have to clear up before it can respond to additional throttle.
Performance here is going to be demonstrated by running fairly clean exhaust output and how little throttle is needed
(manual) to get into first gear without stalling.
(automatic) lose the least rpm when placed in drive. Alternatively have the best vacuum at a given rpm in drive.
Work with initial timing, idle speed screw (transfer slots), and idle mixture screws.

Next confirm off-idle has good performance by very slowly accelerating from stop with no hesitation. This test minimizes the role of the pump shot and focus on the idle circuit's begining of transition.
If that's good, then test more normal acceleration (for public streets) from stop to make sure the pump shot is not too much or too little for this basic job.

Then you can test out steady driving at various speeds. The fuel ratio at steady interstate highway speeds is determined by main jet and its air bleeds. Local highways is partial or completely idle circuit (transition slot, idle feed restriction and idle aiir blleed).
If its too lean, it will surge. Slow down and take it back to garage. Increase primary jets.

If you have access to the strip or dyno you can test wide open throttle in 3 or 4th. AFR is controlled by the jets plus power valve channel restrictions. Change jets for the best mph through the lights.
If primary jetting for best power is different than jetting for best interstate highway mpg, adjust the power valve restrictions.

All the above tests are effected by timing. If you change timing at a given rpm and condition, then retest before change fuel mixture for that condition.

Once all that is tuned, then concentrate on transition conditions. They are:
opening the throttle quickly from low rpm (pump shot).
power valve opening point.

Reality is you may have to go out of sequence. You will almost certainly have to make repeats. How many repeats depends on how much interest and persistance you have.

Good luck!

A little more about AFR for different conditions
Power Valve Selection: The Definitive Answer

I am familiar with the excessive testing for best results. I know only a little about Holleys. I think the jets are part of the idle circuit, are they? I know the cams increase, decrease or lengthen and shorten the amount and timing of the shot of the acc pumps. The squirters effect the amount of fuel dumped by the selected amount of pump shot. And the power valves, I have gotten conflicting information. Some say go with 1/2 the idle vacuum amount for the numbered size of the power valve. But Others say, for more power increase the PV by like 2x one half of the vacuum, which would be at the vacuum full number. I am still not sure what the booster is or how it works, what it effects, or if it can be changed. And the air bleeds are also part of the idle circuit but I'm not sure if they can be changed or not, Not sure if they bleed the amount of air to mix with fuel at all rpm's or not.

I'm going to start with 73 primary, 84 secondary jets, that sounds about right, then 33 or 34 squirters, which ever my acc pump rebuild kit has. I will run 2 orange pump cams with the 30cc pumps for now, and I happen to have 2 6.5 power valves which I will try.

I'm going to soak the metering block and bowls as long as it says to, maybe a little less. and do a complete rebuild of all parts. No sense in sparing a part to get a clog again. It will take a few days, but I will post what I end up with.

I have an AFR Gauge, EGT Gauge, Plan on adding Boost/Vacc gauge to test on highway. It took 10 months to get it built by a pro, that's why the gas is funky. Already ordered the 6AL And a Blaster2 coil. Already have the MSD Ready to Run Dist.

I have a lot of persistence, maybe too much, lol, but I'll get it running right. If there is anything else I need to know about building the carb right, please let me know.

Thanks