Originally Posted by bigdog7373
I've been planning my ls swap for my car but I'm having second thougbts because of costs, plus I need to get the car drivable before summer. So I had the idea of swapping the heads and intake from a vortec or tbi engine onto my current short block. It runs fine but I really want efi for the reliability and mpg's. Will I gain any significant fuel economy from this? I'm hoping for at around 18mpg in the city. Is that number acheivable. It will be backed my a muncie 4speed and I haven't chosen the rear gears or tire size yet so I can pick whatever will be best.
Lt4 is the easy swap lt1 is ok as well. Still cost a pile but will not as much as ls. I fought with this when i was building my 89 vette. I ended up with dumping the efi since it was crap and couldnt be fixed for less than full on replacement of intake injectors and computer and since my car has 300k miles on it the wiring was shot as well. But you may be able to source and lt swap alot cheaper. I would cruise all the local junk yards and ask if the have swaps with engine trans and computer/wiring harnes sensors and all assesories. It is not un common to find these now a days since engine vary so much from model to model its not always a guratee it will work without the computer it was born with, so some mechanics insist on a a full setup just in case even for customer work since even a different injector can killl the engine replacement. And have the mech working for hours extra hes not getting paid for. Ask for a good price what ever they say offer half. Then tell hard luck story and hope for the best.
Its a carbed 360 with older style intake and heads. With the th700r4 it still gets ok milage. Not the same as the ld tpi but it is a lot faster as well. So it was worth dropping to between 15 and 22 mpg. Highway is ok but stomping around town eats up gas unless you baby it.
I would suggest the same thing for you as well. First off the muncie is not going to get good milage. With high gears it will load in low gears and need to be pushed harder to reach normal speeds. With low gears it will always be eating fuel on the highway and not much better in the city but fast.
Th700r4 with most older cars will improve milage. By a few mpg along with a shorter first gear the over drive is really good with 3:55 or 3:73 on the street also works ok with talller gears gm commonly sold then matted to 2 something engine. Shorter first gear makes it roll away smooth with little push of the pedal. Which also helps on the fuel milage.
Also same holds true for the six speed. But the auto is a little faster at the strip.
Sorry for the long post hope it helps.