70 GTO 400 Engine with Edlebrock Performer Intake & Performer Carb

[Michael Jewell]

A former owner had the Edlebrock intake and carburetor installed. While it runs great, it gets horrible gas mileage, less than 10 MPG. Has a stock AT with 3.23 gears. That while driving it modestly. My previous 70, a 4 Spd, with a stock intake and carb, even when I drove it hard, still got in the 12-13 MPG range with 3.55 gears. Is it the nature of the Edlebrock items for the poor mileage? If so should I remove the Edlebrock equipment and go back to a stock intake and carb to get imporved mileage? This car is just for pleasure driving, not hot rodding as I am beyond that stage. Thanks for any advice.
Michael Jewell
[email protected]

 

[melsg5]

Which intake and which carburetor?
Is the vacuum advance connected to a full time vacuum source, manifold vacuum?
What is the initial timing set to?
Is the vacuum line to the transmission modulator connected to the correct port?

 

[cammerjeff]

That has always been my complaint with the Edlebrock carbs, they can be made to run OK, but the MPG will always be worse than with the stock intake & Q-jet (if they are in good working order)

But it still should be getting at least 10 mpg. Does it have the 2 or 3 speed automatic transmission installed? That can make a big difference.

I also 2nd the items melsg5 has asked, that is where I would start as well. But I would also check to see if the mechanical and vacuum advance are working properly. If they are not working correctly the MPG will suffer greatly.