LS swap questions

[bodyman922]

I have an 87 silverado, 350 throttle body injected with 4 wheel drive I am looking to upgrade the engine in. The truck is a minnesota truck with usual rust and is used for the 4 wheel drive and the towing capabilities. It runs good but uses a quart of oil every 400 miles. I was told the motor has never been apart and has over 200,000 miles on it so I would like to upgrade to an LS engine if it is cost effective. I am thinking a 5.3 truck engine from a 1999 and up truck. I am not looking for more power only a truck that is more efficient. It would also help to keep another square alive!

I would like to know from those who have performed the swap if your fuel milage has increased or has stayed the same? Also would like to know if it is possible to keep the stock throttle body injection?

Any info you may have is appreciated. Thanks

[Your41Plague12]

To keep the stock TBI setup you'll probably have to buy an aftermarket carbureted LS intake and use a carb-TBI adapter. If you're keeping the TBI setup and not using the EFI, I'm not sure how much of a gain you'll see. I would bet money it would be worth a few MPG over a worn out small block with over 200,000 miles on it, though!

[Clyde65]

on a 4by I doubt your mileage would improve much, firstly because the drivetrain is staying the same, if you put the 4 speed in, then it might increase on highway. you would want to use what is on the motor, I would holler at John with PCI on a harness that would work well with your existing body harness. also dirty dingo would have the motor plates/mounts you would need. Good luck

[Gregs71]

You didn't say if the truck has overdrive or not and whether its an auto or stick.

What you want to do is probably possible ( 5.3 TBI with stock tranny / TC), the least efficient, but the easiest to do.

The next efficient combo is the full fuel injected (means swapping wiring harness and computer) with stock tranny / TC.

If you have a 3 speed tranny, the most efficient combo is the 5.3 fuel injected ( not TBI) with overdrive. If the 4 speed is a modern 4 speed (4l60/4l80) then you have the added difficulty of mating it to the transfer case. If your running the 700r4, then your mating the 5.3 to the 700r4. If its a manual then and you add overdrive, your back to having difficulties mating a new OD manual tranny to your 5.3 and stock TC.

I have been kicking a round a similar idea. I'd like to hook up a 6.0 to my th400, more for reliability then efficiency though.