Gas Mileage???

brasil said
same story with my ride... getting 11 to 12 mpg on the highway... ( 20 l /100km ) 340 with x heads... 727 3.23 rear... carb doesn´t make a difference... 600 EDE 625 Carter or 800 cfm TQ allways the fuel consumtion
is nearly the same.
I thnik...the igition is the "secret ".... I am tinkering around since weeks with my Ignition curve... and allways...yes allways when I try to bring a vacuum advance into the game... the engine is pinging..under LIGHT LOAD ! at aprox. 2500 rpm....
Think the "problem " is the CR ... perhaps I will pull the heads..the verify the real CR...perhaps I can use a "THICKER " Headgasket...to compensate the high CR

Greetings Juergen

Juergen, I would not suspect high CR to be the problem unless it is 11:1 or higher and is really causing a large amount of retarding of the ignition timing. Higher CR's give better combustion efficiency. I have run 10+:1 SCR and had mileages in the 18-19 mpg range. And others here have done better. Most of the mileage issues are due to carb tuning, and due to the cams selected.