Poor gas mileage...??
#1
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
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
#2
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?
Is the torque converter locking or non-locking?
Is the fuel pump electric and how is the pressure controlled?
#3
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?
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?
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General 1967-2002 F-Body Tech
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10-03-2015 07:27 PM