[Koppster]

This is an old problem I have never solved. My brother now has the car and I'm not sure what to recommend to him, new carb or new dizzy?

64 GTO
76 400 w/ Edelbrock RPM Performer 72cc Heads
800 CFM Quadrajet
Super T10 4-speed
Pertronix Billet HEI
93 Octane Gas
Taylor Wires
NGK 7373 plugs

The car bucks/kicks/stumbles at about 3100 RPM under hard acceleration. Runs fine under normal acceleration. It might be a miss but I have never heard a backfire.

This problem first surfaced about 2014. About that time I changed out an Edelbrock 800 CFM for the Quadrajet rebuilt by a local guy here in San Antonio area. The Pertronix dizzy was on the car when the Edelbrock carb was on, I could really romp on it

Timing: 12 BTDC static/about 30/32 Total Timing all in around 2500-3000 RPM. However, the timing jumps about 2 degrees under RPM

Wires were replaced during the Edelbrock era and they worked fine

Thoughts?

Thanks
Rick

Here's a quote from the guy who built my Quadrajet if anyone is curious about jetting/etc.:
"Some of the modifications that I do are proprietary such as the resizing of the internal orifices, channel restriction modifications, etc. There are about 40 different machining tricks that have to be done. All Quadrajets after 1973 were made to give lean performance to meet federal laws on emissions. That's why you can't just bolt on a stock Quadrajet and expect it to work on any engine that is not completely stock even if you change the jets and rods to bigger sizes. It still wouldn't idle right and there would be a bad hesitation when you accelerated. Jet and primary rod sizing is selected to match your engine combo. Yours would be #72 jets and APT type rods that are .041 to .044 with a .026 power tip. I include an APT (adjustable part throttle) adjustment tool to tune the carb for the best off-idle and cruise performance. The secondary hanger and rods are selected depending on the cubic inches, any head porting done, type of cam, differential gears, transmission, etc"