Quote:
Originally Posted by pastry_chef
Disagree, pure highway cruising we got just over 20 MPG.
80 Firebird with two men. 455 engine - 310 CFM heads, hyd roller, 2004R with PTC 3200 stall - locked up. 56 Miles/ 10.2 Liters of gas consumed. RPM was right about 1700 RPM for the drive. Owner spent many hours tweaking the fuel and timing curves. Autometer speedo was calibrated less than 1% error.
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My experience as well. '67 GTO convertible, TH400, 2.56 rear gear, stock Q-jet, stock distributor, original 400 engine with small valve #15 heads for 9.3CR. Average for the past 8 years or so for highway drives is 20-21 MPG at sustained 75-80 mph, and best was 23 mpg on a 140 mile run at a steady 65 mph. My '65 GTO with a 4 speed and a 3.36 rear gear with tripower gets 15 mpg highway at sustained 70 mph. If you're not blipping the throttle all over the place and are steady and smooth, not an issue. Around town, not so much.