Quick Fuel Carb

[edison1970]

After numerous jet changes, pump nozzle replacements on the Holley Street Avenger 770, I decided to try a QFT 750 DP. My motor is a 440 , 30 over, lunati 703 cam,  six pack pistons, closed chamber cast iron heads, RPM intake and super comp headers. Fired right up but is too rich. This is where things started going south with the other carb. The mains are 72 and secondary have 80s. I was going to drop the mains down to a 70. Is 2 sizes down seem adequate?  The Holley had 65s in the mains when I started.

[screamindriver]

Two jet sizes is usually the minimum jump for fine tuning so you can keep jumping down until you're there...How are you getting your results ?? Plug reading ?? wide band A/F gauge ?...Did you get as far as where the rich condition occurs{idle,cruise,acceleration} ??? Did you get a spec sheet for the metering block with the restrictor  sizes ??

[JS29]

This may sound strange, I have made repairs to engines that were running like crap, and were sill not running as well as i liked. took the vehicle out and drove it for a while and it seamed like it had to clear it's self out. I had made the correct repairs, It just had to clean up. I have the same carb on my 383 and it seamed rich at first   

[Chryco Psycho]

I guess I will never understand , the 340 had a 800 cfm TQ from the factory why use a 750 on a 440 
Proper tuning is everything , simply the most important part of extracting HP

[edison1970]

Please explain. I would think that the larger cfm would be determined by intended use of the vehicle? I have a crate full of Thermoquads but I was hoping to be able to fine tune this carb than the other. I'm no carb expert. Just looking for a fun street cruiser.