Hello everyone. I have an '89 Corsica with a 2.8 and the crankshaft broke in half the other day. I'm looking to put in a 3.1 with a 4T60 transmission. I'm going for fuel economy more than acceleration.

My main question is this: does anybody have a BSFC chart for this engine? I can't find one anywhere. I just want to get an idea of what I'm going to be looking at. I also need to find out if the 3.1 can pull the car along at 70MPH at 1700 RPM. The transmission I want is the 33/37 (or 37/33, but the point is that the ratio is .89). According to my calculations, with my tire size, the engine RPM I mentioned is accurate. I'm told that in lower gears, I should be good to go as well (the car should be able to get out of its own way).

So, I'm just looking for that chart, and if anybody things this is an awful idea, please feel free to chime in! Thank you!

i had a 90 GP with that engine and trans not sure about the ratio but with 225-65-16 tires, it was about that rpm and speed. i always got over 30mpg at 70 all hwy. if i keep it to the speed limit 33-34. i had a 2.8 firebird and 2.8 cutlass they all had about the same power. basically nothing to be proud of but if you need to go it would shift and not going to get run over. they were made for fuel economy and designed to run properly at that low rpm, saves gas