its a 750 holley and it's on top of a mild built 350, is it too big?? i'm getting about 11 mpg right now whenever i crack open the 4 barrel alot of cas pours out the pipes, should i go with a 600??

 

I just went from TPI to carbs and everyone I talked to said a 750 is too big. I went with the 650 double pumper. It's almost running so I'll get back to you with the ET's. Mine is mildly built also, flat top hyperutectic pistons bored .030, edelbrock performer intake, elgin cam .462 intake .470 exhaust, heads and block decked, World Products S/R torquer Heads

 

750 isn't too big. Besides which cfm rating has absolutly nothing to do with "gas pouring out of the pipes." If it's running too rich then you have a physical problem or tuning issues.

 

I'm running a 750 DP on mine, and everything is okay except for a slight stumble upon the pedal hitting the floor. I need to tune my seconadary pump cam I believe. Throttle response is excellent also.

 

I'm not running a double pumper but my vacuum secondary 750 Holley ran 14.4 right out of the box. Now I've re-jetted it and put in a stiffer secondary spring and it pulls a lot harder (very very low 14s, hopefully). I can't give exact gas milage cause I broke my trip odometer but last week I drove 45 minutes away on back roads (stop and go), raced a couple of times, then drove back and still had a full tank of gas. Everyone says "a 750 on a basically stock 350?! thats way too big" ......BULLSHEEEET. Good performance, good milage, good throttle response ...absolutely no complaints

 

how about having # 74 jets in it, would that kill the mileage? when i stand on it alot of carbon/fuel/oil comes out my exhaust everyone of these is accounted for except the fuel i think i may have to re- jet it thanks for the help though i'm new to this whole carb thing.

thanks

 

Buy the big pack of jets from Holley for $20-something dollars so you have like every jet from #64 to like #99 and just start reading your spark plugs. Keep going down a size or two until you get it just right with no black smoke or spark plugs. I'm running good right now with 68 jets in the primaries.

 

If I remember correctly I have 69/74's in.