Can I swap 350 for a 454?

Guardian · June 18, 2003

Recently blew up the 454 in my 91 3/4 ton 4wd. truck. Does anyone know if you can swap a 350 in place of the 454? Will it bolt up to the tranny? Will the computer hook up to the new engine?

Thanks for all the help

Rob Simmons

(Soon to be owner of a 2003 Duramax duelly toy, I mean work truck!)

americanmuscleman · June 18, 2003

You can put a 350 in, but it would be a lot easier to put another big block back in. To put a 350 in, you would need to change motor mounts, computers, manifolds and exhaust, and all your engine accessory brackets and some of the accessories. Wiring harnesses are going to be different, and will need to be modified, as well as throttle linkage. The tranny in a 91' 3/4 ton is a 4L80 (no "E" which stands for electronically controlled), so hooking a small block to the front of it won't be difficult.

If I were you, I would just find a used TBI 454 out of a wrecked truck or out of a junkyard and swap it into your truck.

Just my 2 cents

BDBWTE · June 19, 2003

It is a possiblity to change out a 454 to a 350 but you would save yourself a lot of head aches just putting a BB back in. You will most likely have to get a new wiring harness and computer, brain box, etc. The tranny will bolt right up no problems. putting a 480LE instead of a T350 will work but the 4L80E is longer because of the extra gear and will mount a little different and thus new mounting hardware and shorting the drive line and adjusting some linkage will be necessary..

Hope this helps

BDBWTE