1991 k1500 swapping 4.3 out for 5.7

[55Willy]

Just seeing what is needed for the swap.
I can get a sweet deal on the truck just needs a motor and instead of rebuilding the 4.3 i'd rather drop a 350 in it and keep it TBI.
would the TB work if i had bigger injectors in it? what about the computer?

 

[kennyw]

I'd guess the computer won't work as you have 2 more spark plugs to control that were not there before... to be honest I think the cost of the swap would be more than buying the same truck with a good 350 already in it.

 

[55Willy]

$500. comes with the 4.3 and a 90 350 rebuilder. I'm now thinking of yanking the 350 out of the cop car with that computer and TB put that in the truck and then rebuild the 90 350 with the cop car tranny for the suburban. sounds like a lot of work and more projects...just what I need,LOL

 

[kennyw]

What is a good running '91 K1500 worth out here? $2000? You will spend $1000 rebuilding the 350, plus the cost of a computer and wiring, not to mention your time. I think you would be money ahead to just passing on that one unless it was to put a used 4.3L back into it cheap. Then resell it and pick up one with a 350 already in it.

 

[Jason4x4]

I really don't think it would be alot of work. IIRC, the harness is the same, just swap the TB, The ecm, and fire it up. should be pretty simple.

 

[b454rat]

Swap out the computer, the harness is the same, just some of the plugs might be a little different. There are enough of these trucks out there to get any parts that you might need. I'm gonna be swapping in a TBI 454 into my 92 Blazer soon, can't wait!!!!

 

[90_K5 Blazer]

Just fyi, the throttle body on a 4.3 does flow less than a 5.7's. In fact, when GM built the syclone and typhoons, they used a 5.7 throttle body on the 4.3 because of the turbo.