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