Swapping 4.3 to V8 engine

[all_niter]

I have a 1991 GMC Sierra truck. It has a 4.3 V6 with 5 speed tranny. Would it be possible to swap this V6 for a 305 or 350 V8. I would like to swap without changing tranny. Would it bolt up easy or with modifications.

[quaddriver]

Originally Posted by all_niter

I have a 1991 GMC Sierra truck. It has a 4.3 V6 with 5 speed tranny. Would it be possible to swap this V6 for a 305 or 350 V8. I would like to swap without changing tranny. Would it bolt up easy or with modifications.

yes but u need new mounts, ecm, harness, radiator

[ScottG]

I helped my brother-in-law perform this swap on an 89 GMC Sierra a few years ago. It was alot easier than I thought it was going to be. I believe we did change the motor mounts and radiator as stated by the previous poster. However, we did not change the the wiring harness. If I remember correctly, all we had to do was get the chip out of a truck with a V8 and swap chips. At least on the 89 model, the computer is behind the glove compartment. There is an access panel with two screws that you remove and the chip slides right out and slide the new one in. The motor bolted right up to the standard transmission. I think we had change the flywheel because the motor was for a truck with an automatic.

[kenny8869]

yes all you should need to do is change the engine mounts for a 305 or 350 also you need to change the prom chip in the computer for whatever v8 you decide to run you also might want to run the throttle body from the original engine otherwise it will probably run to lean

[12gauge]

EVERYONE FORGOT WHAT IS PROBABLY THE MOST EXPENSIVE PIECE OF THE PUZZLE.

THE HEADERS-I THINK YOU NEED CUSTOM SHORTY HEADERS, I KNOW SO IF ITS A 4X4. BUT THE GOOD NEWS IS THAT EVERY ONE SELLS THEM. LOOK THROUGH THE PAGES OF SUMMIT TO FIND PRETTY MUCH EVERYTHING YOU NEED.

ID SAY YOU ARE LUCKY IT HAS THE 5 SPEED OR ELSE YOU WOULD NEED TO SWAP THE TRANNY FOR A TURBO 350

IT MIGHT BE A PAIN BUT IT WILL BE WORTH IT IN THE END
-12 ga