Poor gas mileage...??
 

I've owned my '81 Z28 for a few weeks and the gas mileage seems a little high to me. Since I'm new to the car I've driven it easily so far.

Here's the spec:

ZZ4 crate engine, trick flow ally heads held down with an arp bolt set on top of ultra thin metal head gaskets raising compression to 10.5:1, trick flow cam, trick flow hardened push rods, Weiand stealth warrior dual plane inlet with a 750DP Holley carb fed by a 110gph Holley fuel pump, upgraded Davies unified ignition HEI distributor, new rotor arm, new leads and new plugs, full length headers into 3 inch collectors with exhaust dumps, power now estimated @ 460+ bhp all kept cool by a 3 core ally be-cool rad and steel flexi fan with billet reduction pulley, also new battery and alternator just fitted

Drivetrain
Rebuilt TH350 with B&M 3200 stall converter, shift kit, external cooler, and quick silver shifter
Rear end is a rebuilt 10 bolt posi with 3.90 gears

I'm getting 4-6 mpg which I figure is too low, but then again considering the spec and gearing is it?? I will say a fair amount of town driving has been involved, and I have noticed at 70 mph the engine is around 3500 RPM.

Any ideas? Thanks :)

Re: Poor gas mileage...??
 

Have you checked the plugs since they were replaced? Using that much fuel, they should be black.

Is the torque converter locking or non-locking?

Is the fuel pump electric and how is the pressure controlled?

Re: Poor gas mileage...??
 

Wondering if you've ever had it tuned to see if it's running rich or not, properly jetted.

I had a plastic float sink once in a quadrajet, that caused a lot of fuel to flow. Got it rebuilt and fixed that problem. Since you're using a Holley I'll guess it's not the same problem but worth checking on. But what do I know?