the OD gear is more like a 5 speed with No 4th. when doing these averages, its at 55mph should be No or No less. when you increase the HP on a motor, you most likely substitute mpg's. or go over 55 mph.
No O/D not mine, documented from 1964. If you read the article, it describes conditions, and that these were off the lot cars with strict fueling and non tampering policy. LOL that you guys can't believe some of the stuff that some of our members have achieved. Mine by efficiency as I was building for power, not fuel economy.
