I have a '65 Coronet with a 514" Hemi, Mopar crossram with 2 Holley 770's. Footbrake car. I have tried 2 converters and the current one will only allow a launch of 2600 rpm. On the hit of the throttle the car stumbles and actually spits back thru the carbs which is visible when we try with the hood off. It will stumble for a bit maybe 100 -150 ft. and then take off like a rocket and run almost 140 mph.
Now for the things we have tried are two different sets of carbs and going lean and fat with both. Different ignition wires. 3 different types of plugs. Different MSD 7al2, Compression test, Leak down test, Crank trigger, crank trigger wire, reroute crank trigger wire to avoid RF. By pass crank trigger and use distributor.
We did find a broken intake valve spring and thought great that's it. Went to a track rental this past Monday ready to make some good hits and had the exact same problem.
We have spoken with several engine builders across the country and they have all taken the time to listen to everything. After they have a while to think about it they have all said it sounds like everything is right.
We degreed the cam a while back and we are going to check it again today just to be sure because it really acts like the intake valves seem to be closing a little late.
I posted this today as it marks my 3 month anniversary since I first took this car to the track and we are no closer to a resolution.
Any thoughts would be greatly appreciated. Thanks in advance.

Charlie Moore
440-846-3777

It really sounds like your accelerator pump and squirters
being its right at the hit... is the pump arm moving
as soon as you move the throttle blades
EDIT
Whats your timing at

The squirters have been replaced with larger and smaller ones. The cams that push on the accelerator pump arms have been replaced and modified to give the major shot after stage rpm. Thank you for the input.

Timing has been tried anywhere from 29 degrees to 35 degrees.

Will it it free rev without the stumble

When I try to free rev it, it will go to about 4000 rpm and stumble momentarily and then jump up.

I'm not 100% sure what you mean when you say spray the intake? I've heard of it, but what are you spraying it with?

I really appreciate this. We noticed that the idle air bleeds have been changed to make them replaceable. We noticed that adjusting the air/fuel mixture did not affect the idle much at all. We assumed the air bleeds were just to big but there maybe a leak. I will try this after I put the front of the engine back together. Thanks again.

With this creating a super lean condition on the opening of the throttle, have you seen it start spitting back like I tried to describe?

My uneducated guess is the problems are in the vacuum secondairees maybe opening to fast and maybe too lean or rich at first.

That could be an air bleed problem not allowing enough fuel in right away.

probably opening too fast and too lean combination??

So he says lean and fat if it goes lean then fat it sure could be the secondairees coming open too soon lean with no air flow no initial flow from jets then maybe fat because of jetting and or air bleeds??

So one easy test would be to go 1/2 throttle at the hit and feed it the rest of the throttle over 60 to 80 feet if that smooths it out it's most likely all in secondary opening and jetting/air bleeds.

The carbs were set up for a crossram and the second set we tried came off a crossram. We just checked cam timing. Bullet says this cam should be at 109. It was installed at 110.5. It has a Cloyes Hex-adjust cam gear. So I loosened the 3 gear bolts a tried to adjust adjuster cam within the cam gear and sure enough it cracked. I guess I'm done until Tuesday when I can call Cloyes. I greatly appreciate everyone's feedback and suggestions. I'm going to Norwalk now just to watch some cars that actually run. Thanks, Charlie.