t56 mpg question 454 bbc vs ls1/ls2

[BlindSideCustoms]

okay guys so im planning out my project here and i definately want to use a t56 since it would give me more gears to work with so i could still get decent mpg on the highway. but my real question is once you start building a lsx engine for 600-700hp how much would the gas mileage differ from a 454 at the same horsepower? i mean not wanting a exact idea but would it be drastically different as in more than 5 mpg difference. i know that stock vs stock the lsx engines are more efficient but once you start building one how much of a difference is their to a bbc if mated to a t56 tranny.

[MarkM66]

Both at same CID, same power output, and both properly tunned. Advantage on paper to LSX. Go with the one you'd rather have, mpg isn't going much different between the two.

[streetk14]

The question I have for you is how are you planning to go about making this 600-700 hp out of said LSx motor, cubic inches or forced induction?

An LS1 or LS2 with forced induction could get you the power you want and get good mileage to back it up. You could also do a fairly mild LS7 and probably hit 600 hp. The LS7 gets 24 MPG highway in the Z06 stock. With a mild cam upgrade, exhaust, headers, ect., I wouldn't think it would hurt economy too much.

I know al lot of Vette guys out there running Magnacharger blowers and knocking down economy that is close to stock LS1/LS2 numbers. I don't really know what my car is doing yet as far as MPG, I've been having too much fun roasting the tires and such. But it has a 600 hp LS1 based motor with 4.11 gears and has to get somewhere in the 20's on the highway.

I'm really going to have to take a little freeway trip without any full throttle to see what it can do.

Andy

[BlindSideCustoms]

hmm thats interesting....considering i was going to be running somewhere around that gearing not sure yet. i just want something to run like a raped ape when i want it to and then get good mpg on the highway for rides to shows etc. it kills the fun in driving a car if you know your spending 40 bucks in gas to take it out for a daily drive lol.