fuel mileage with 750 quadrajet

[shadetree55]

maybe dumb question but is there any way to make a 750 closer to a 650?  Running a bone stock 305 in my 55 with a 700R4 and don't want performance, need fuel mileage.

[Mudsport96]

You will see better mpg with a 750 quadrajet than you would with a 650 holley or edelbrock. Just tune the primary side correctly for your application and you will be fine.

[shadetree55]

I've only got 250 miles on new crate motor and the carb I rebuilt with I'm assuming is stock jets and metering rods for the primaries. I bought it used and it had already been rebuilt by Holley, had a tag on it stating so.I went ahead and rebuilt it myself just to be sure everything was clean and good.  I'll pull it after I get some more miles on it and see what size the primaries are. I don't want to lean it out much. It performs well for my driving needs.

[77cruiser]

If it's been rebuilt by Holley you won't get very good mileage, I think they butcher them.
Find a unmolested one & rebuild that.
What do you get for MPG now?

[Mudsport96]

Also, knowing the rest of the setup can help us help you.

Car

Engine

Transmission

Final drive

[shadetree55]

stock 305 , 700R4 3:55 gears.  haven't driven enough to really check mileage, only have 229 miles on the new engine

[Mudsport96]

I would recommend getting some miles on the car, and with an accurate mileage reading between fill upstairs calculate the mileage. Without knowing where you are starting, you can not make a judgement on whether or not it is getting reasonable mpgs or not. And on top of that, as the engine breaks in and rings seat, it is possible that vacuum signals to the carb will change. Thus negating and changes you make now.

[lightning boy]

Don't ever buy a carb with a rebuild tag on it.

[Cliff Ruggles]

+2, 3 and 4 on that deal.

Holley is the WORST company next to I-5 to ever touch a Q-jet.  They are "hacked" up Frankencarbs so not surprised if it's not up to par for what you are doing......