For decades, GM’s Gen I small-block was the go-to engine swap for anything that needed cheap, reliable power, but its reign is coming to an end. GM’s Gen III V-8 debuted in the new-for-’97 C5 Corvette, and during those 14 years it has been installed in North American vehicles from Chevrolet, GMC, Buick, Oldsmobile, Pontiac, Cadillac, Isuzu, and Saab. This widespread use means that complete engines can be found in wrecked vehicles in salvage yards from coast to coast. The power potential, efficiency, and availability of the engines makes them a natural selection for swaps, but there are some hurdles to overcome. For example, the Gen IV small-block was ushered in with the LS2 and while the Gen III and Gen IV engines share a common foundation and offer a lot of parts interchangeability, the electronics, fuel systems, and emissions systems can vary from year to year and between applications. We’ll help you sort out some of the confusion and put you in touch with the people that can answer your specific technical questions.

In addition to giving you the ins and outs of common LS engine swaps, we’ll also give you a quick look into common LS engine dress-up parts. To help us get exactly what we needed, we contacted Stylin’ Trucks and placed an order to match the engine we were swapping in with the truck year and make. Thankfully, the 2000 Silverado that originally came with a 4.3L V-6 also came with the optional 5.3L V-8, which we picked up from a local salvage yard for under $1,000. Once the must-have OE parts were secured, we dressed up the 5.3L with good-looking performance parts and had our Chevy ready for cruising and showing. See a full step-by-step LS engine install in next month’s issue. Now you should have the confidence to swap in some real power and slam the pedal to the floor.

What about the transmission?

TCI and Advance Adapters both make flexplates that allow you to keep your Turbo 400 or Turbo 350/700-R4 transmission. The companies listed in the Source Box also make wiring harnesses that can help with late-model swaps. To make things really simple, a manual transmission will solve any late-model automatic computer problems—and they’re more fun.

How do I get my gauges to work?

If you’ve got a late-model GM truck that needs a V-8, Speartech can provide you with an in-line plug-in adapter that keeps your factory gauges and A/C working. For older vehicles, Auto Meter makes speedometer-sending units that thread into various transmission tailshafts.

Most LS engines use an electronic “drive-by-wire” throttle body like this one from GM Performance Parts’ LS3 ECU kit. Unless you’re using an older cable-operated system, you’ll need the pedal to match the wiring harness.

For more information, contact:
GM Performance Parts
Crate engines, wiring harnesses/ECUs, vast array of LS engine parts.

Throttle bodies changed connector plugs from Gen III and Gen IV generations; an adapter is available from Torque Rush Performance to convert the factory truck 75mm throttle body to the newer 90mm throttle body from an LS3 or LS7. It’s plug-and-play.

For more information, contact:
Torque Rush Performance Inc.
(204) 232-3118
Throttle body wiring conversion for 8-pin to 6-pin applications.

Here’s the cam position sensor on the front timing cover of a Gen IV LS3 block. On a 4.8L, 5.3L, or 6.0L Gen III, the sensor will be at the top rear of the block. If your computer and engine are from two different generations of engine, you’ll need an adapter that can be picked up from Lingenfelter or Speartech. Lingenfelter also makes a reluctor wheel conversion harness that works great and converts the truck 24X wiring harness to the newer 58X reluctor wheel. We’ve used it, and it’s worth its weight in gold.

For more information, contact:
Lingenfelter Performance Engineering
(260) 724-2552
Wiring adapters for Gen III and IV GM engines.

Speartech Fuel Injection Systems
(765) 378-4908
Complete powertrains, transmission, wiring and gauge solutions for swapping between 24x and 58x LS engines.

One vitally important thing to consider is fuel delivery. LS engines need at least 58 psi of fuel pressure for optimum performance. If you’re swapping in a fuel-injected LS into a carburetor-equipped truck, a fuel cell may be your best option. Aeromotive sells a fuel cell/pump combo that will support up to 1,000 hp. Fittings and high-pressure fuel hose is also a must and Earl’s makes a huge assortment of hoses and fittings. Fuel injectors also vary from Gen III to Gen IV LS engines and Speartech makes the appropriate wiring harnesses to convert them if the need arises.

For more information, contact:
(913) 647-7300
Fuel cells, fuel pumps, and fuel fittings.

Earl’s Plumbing
Fuel hose, fuel fittings, and adapters.