cfg83, that is exactly what I calculated, 20 mpg. And thanks for the spread sheet. I know v-8's can get good gas mileage. My buddy had a 97 Z-28 with a v-8, 3.42 gears and .50 OD. We got 33 mpg out of a highway trip from Frederick, MD to Baltimore, MD. It ran 14.00 in the 1/4 mile. It was bone stock.
This is for the people that didn't read my first post very well.
I understand that the two cars don't compare very well but, I just don't understand why there would be such a HUGE difference. The 3.73 gears compared to the 2.73 gears is a big factor. The tire height is the same, although the 442 should have less rolling resistance because the tires have a much smaller contact patch (215/65/15 for the 442 and 235/60/15 for the Firebird) and also, the 442 has slightly more OD. .67 to .70.
I thought it was running rich as well but, it doesn't smell like it is. My Omega was running rich (burns your eyes out!) as a you know what and still getting 10-12 mpg without OD, 3.73 gears, 468 cubes with a non-computer carb, weighing 3620 lbs and a Cd of who knows, maybe .50?
I must have a fuel leak!
(on the 442)