I have a 460 big block and am currently running a holley 750 double pumper, front jets are 70 and rear jets are 85, it is running too rich. Any suggestions as to what size jets would be appropriate for my application.

 

Maybe try the FTE fuel delivery forum ?

That's what that forum is for. General forum for questions like >To match fuel flow to engines

IMO, that is way too much CFM

Jet it for about 580-600 Cfm is plenty for street use

 

Like Mil1ion said, that's alittle to much CFM.

Unless the motor was built to perform and has a big cam, high CR, ect... 750 is alittle to much.
For stock 600 CFM would be good, for a mild build: 600-650 would be fine too.

 

A double pumper works great for racing but not on the street. I have seen that setup too many times on the street.

 

I'm not an expert, but baseline carb sizing can be calculated on the link below, assuming the volumetric efficiency of the motor. Using the link below, a 460 with a max of 5000rpm, you would need a 666 cfm if your volumetric efficiency was 100%, 566 cfm if your volumetric efficiency was 85%. Like Torque1st says, on a truck, you would probably be better off with a 650 - 725 vacuum secondary carb?


http://www.4secondsflat.com/Carb_CFM_Calculator.html

 

i've tried a 650 on it and it just seems to starve. it does have a mild cam and has been slightly modified in other ways. It is my daily driver tho. i've had this carb on there for a few years and never really had any problems out of it til now. I was having a few problems with the heads and had to drive another vehicle so in order to do so i pulled that carb off and stuck it on a chevelle (which runs like crap but what do you expect if they sit). anyway i got my head problem straightened out and put the carb back on my truck and started having the problem. The chevelle was having a few backfiring issues so i though it might of tore something up in the few days it was on there so I put a rubuild kit in it. Runs lots better but that's when it started flooding. is there anything aside from the fact that you don't like the setup i run that could of caused this? if it was the size of the carb i would think it would of been doing it all along, and it wasn't. thanks for the ther forum i'll try my luck there too.

 

You say too rich. When is it too rich. Is the idle circuit too rich? Intermediate? Fast air too rich? All of the above?
Double pumpers are only bad for the guys that don't know how to tune them. A guy with a little patience, and some time can make one work well, and not just for race applications. The Holley is a great carb, and easy to use once you understand it. Have you picked up a book describinng the Holley carb?
Does your carb have 2 metering plates that are adjustable?
Chances are you will change jets but it will still idle too fat. This is because the idle air bleed orifices are sized incorrectly. These are located inside of the choke horn.
I use Holleys on plenty of engines. Mine do not require chokes, start right up even in the cold, in fact the choke horns are no longer there. They idle well, have fantastic throttle response, and are very driveable.
Yours can run very well too, it just needs a little work.