My 340 getting 6 mpg

64whiteghost said
Whata up guys !

A little update on the 64whiteghost aka my 1964 plymouth valiant.

Got my 340 running and broken in i havs about 150 miles left to hit the 500 miles. But i have one problem. Im getting 6 mpg

Im running an FST double pumper 750 with 67 jets. Idk what power valve yet. But im assuming it has the stock 6.5.

Motor: 340 .30 over

Cam specs: See photo. It is a custom cam and peak power is at 680p rpm

Cylinder heads: flow bench showed 235cfm

Rear: 8 3/4 3:73s with a posi

Im wondering if my 750 is too much. Power is crazy good and im happy with that. But my mpg is insane lol And im wondering if i need to go down to a 650 and if that would help.

Thoughts?

In wondering

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I have a 340 Duster running a Holey 750 double pumper primary jets 72, secondary jets 76 power valve 45 Edlebrock LD340 intke. Your jets are too small so you have to push the throttle so far that you are always into the power valve. What is your elevation? I'm in southern California pretty close to sea level. Your cam sounds like it is a little too hot for the street (Sig Erson hyFlow 2?) The Sig hyflow 1 is a better choice. My Duster gets 12mpg with 3.55 gears with posi and the stock cam (hydraulic). I have a 4 speed. It turns low 12's/high 11's depending on the track.
If you have an automatic, what is the stall speed on the converter? My V-8 Vega has a 700R4 2200 rpm stall, 3.08 gears with posi and Sig Erson HyFlow1 cam with Fuel Injection. Both cars have headers.