Originally Posted by 85Sierra
Well i have had the car out for a week now and it gets worse mileage then my truck even when i dont give'r, There is a 600 holley rebuilt in the local buy/sell for $100 might check that out
How much time have you spent dialing in the carb? Q-Jets are good but they aren't magic....... and the same goes for any carb you might try. You might get lucky and come close but the odds that it is optimal are pretty slim.
Also you may not believe this but with your combo that 2.73 might be hurting your mileage, a lower gear like a 3.08 or 3.23 may actually improve it and it certainly won't hurt the performance. With your cam you're probably having to give it a fair amount of throttle to get it rolling because it's not "up on the cam", in other words it isn't in the "fat" part of the torque curve yet. A loose converter doesn't help mileage either. A lower gear will help the torque multiplication and get it into the torque curve at a slower vehicle speed plus keep it in the curve at cruise RPM. That's where an OD transmission, lock up converter and a lower rear gear can really shine. I know there's a lot of argument that keeping engine RPM as low as possible is the key to good fuel economy but it's only part of the story. New cars are geared so incredibly high at least in part to reduce "emissions per mile", a slightly lower Final Drive Ratio in many cases would give better economy but increase emissions per mile. For example my '94 LeSabre has a 2.84 differential plus 30% OD for an FDR of 1.99 to 1
. It gets 25-26 HWY MPG when driven at a steady 55MPH, at a steady 70 MPH it gets a consistent 28-29. A swap to a 3.08 differential would boost my 55MPH gas mileage to 28-29 or even a tad better because of less wind resistance even though it increased engine RPM. I do most of my driving in that car at 55-60 and if it didn't have 176,000 on it I'd be swapping the differential. It's a piece of cake on a 4T60E.