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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: steve bloom on September 21, 2025, 08:53:14 pm
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Hi all, I am new to the site, I have a stock 87 short wide square body GMC, the engine is tired and I’m looking at doing either a factory rebuild with perhaps performance upgrade or an LS swap? I would like to hear, opinions and thoughts, both pro and con. My understanding is they are not too many performance upgrades for the factory 350 TBI with the 700 R4 that is in the truck at present. I have been considering an LS swap that I am not sold on it just yet. I’m sure some of you have had experience in this and I’m trying to learn more about the process of doing a LS swap, or trying to rebuild the factory TBI and get better horsepower and performance. Thanks for any comments or suggestions in advance.
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Well Stevey,
First, congrats on the truck! Is it a fleet or stepside? Pics please?
You will certainly find a variety of opinions here. Major brain trust...
Truthfully, I am ignorant of the evolution of the LS transition from what I perceived was the move from SBC's. I think Vortec was involved somewhere in there as well.
I may be wrong about this too, but I will use AI to edumacate me.
Hope this board wakes up soon....
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I would drive it until the engine is leaking or burning so much oil that it really bothers you then:
-Rebuild the current engine to near stock specs OR
-Drop in a new crate L31 engine
LS swap is for people heavily invested in their vehicle or large amounts of money. Stock or near stock rebuild or crate is your most simple option to get engine back to 100% with least amount of down time. Not sure about you, but I much prefer DRIVING my cool old vehicles than constantly WORKING on them.
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The truck is a fleet side, 700 r4 Transmission dual tanks, tilt Cruz AC electric windows, the engine doesn’t run bad but it’s tired. It’s got a lot of miles on it, I’m debating between an LS swap or just a rebuild of the present motor. I’m curious of what type of upgrades could be done to a TBI system. that would give it better horsepower and performance without turning it into a gas guzzler?
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Begin with the end in mind...When you open the hood, what do you want to see there? How do you want it to perform? I've seen enough hacked krylon rebuilt LS swaps in these trucks that it makes me ill so if you are looking to be budgetary, avoid this route unless someone is gifting you everything you need. On the flipside I've seen many many nicely done LS swaps that look splendid in their new house and they're fun to drive too. I've built many of them myself and at this point personally I still favor the SBC/BBC in these trucks just because I like the period correct look and feel. I just took my 74 out for a joy ride (454) and can ignite the tires at virtually any second with endless gobs of power and period correct engine in it's hut. When I open the hood, I see what I want to see. That being said, some people favor LS swaps for the versatility and plethora of options available to customize or source parts. Flip it again and if EFI is your draw, you can't go wrong with Holley Sniper 2 or Terminator setups either. Decide what you want the end result to be and then plan from there. The beauty is the sky is the limit and it's your truck to build it the way you see fit.