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One of the most popular LS swap recipients today are the light truck lines offered by Chevrolet and GMC. The C/K series of trucks and utility vehicles were introduced in 1960, with a second generation running from 1967-1972 and a long lasting third generation that carried from 1973-1987. Holley and their supporting brands have been studying and building C10s for years and offer a plenty of performance upgrade products, as well as an inclusive list of LS swap components.
LS swaps are nothing new, but there’s a difference between reading about them in forums versus finishing one right the first time. Planning out an LS swap by mapping out the parts you’re going to need to complete the installation will pay dividends once you start turning wrenches. Buying mounts from company A, headers from company B, with a crossmember from company C can add up to an overall fitment issues as the parts weren’t designed to work together as a whole. It’s best to work with parts from one company all the way through.
Not only does Holley continue to roll out helpful new LS swap components, but they work together with a number of their sister companies to develop products that are engineered, tested and built to work together. This means you get parts that fit right and perform to expectation to help you achieve a professional drivetrain swap
We decided to put their list of C10 LS swap parts to the test by swapping a late-model powertrain into a 1971 Chevrolet C10 Suburban. The ‘new’ driveline was liberated from a totaled 2003 Chevrolet Tahoe. We were able to start the 5.3L and even putt the wreck around the yard before deciding it would be right for our ’71. The engine had about 110,000 miles, sounded good and the trans shifted from what little we could tell and had healthy appearing trans fluid. The swap was a go.
For electronic control, the Terminator X Max was our go-to decision since it has trans controls built into the ECU. The system is easy to program with its handheld monitor, plus we’ll have the capability to plug-in our laptop for some advanced trans tuning and other controls. The Holley site made it easy to boil down exactly what part numbers we needed including the ECU, the injector harness, drive-by-wire harness and more.
The site also has pages dedicated to LS swap applications, including our ’71 Suburban, so it was easy to scroll through the site and find engine mount systems, headers and manifolds, cooling system solutions, fuel system solutions and more. Follow along as we detail our C10 LS swap.
Our subject is a 5.3L from a 2003 Tahoe including its 4L60E trans. The LM7 coded engine had about 110,000 miles when we pulled it so we didn’t bother to update any of the engine’s mechanicals, but it did require a serious clean up. (We have about as much time in degreasing the engine as in the installation!)
Out came the ‘updated’ drivetrain of our C10 consisting of a well-worn TBI equipped SBC 350 and 700-R4 transmission. The engine ran okay with a little knock at start up but the 30-year-old EFI was becoming problematic. Good riddance.
The factory oil pans from trucks are extremely deep and will not fit most LS swap candidates. A cast aluminum Holley pan, PN 302-2, is designed with a low profile to clear most GM crossmembers from ’55 – ’87. Holley offers a kit, PN VK090001, which includes a one-piece molded gasket, stainless hardware, dipstick, and even RTV.
The factory oil deflector tray needs to be modified slightly to accept the new pickup tube assembly. We simply cut the tray down 14.25” and added a slight notch to clear the new pickup tube. The photo on the left is the stock setup to compare to the modified tray on the right with the Holley pickup tube installed.
The cast aluminum pan fit perfectly providing the structural integrity and bell housing attaching points that are expected of an OEM pan. If you’re running an LS7 or a modified engine with over a 3.62” stroke, this pan can’t be used but for our stock LM7 and C10, it was perfect, as you can see in the image on the right.
To mount our new engine, a set of Hooker Blackheart’s heavy duty clam style mounts were used. These assemblies are modeled after the ’98-’04 GM F-body design. Thicker steel is stamped into the clamshell assemblies (PN 71221018HKR) to surround a hearty polyurethane insert (PN 71221016HKR). For the engine compartment, a set of Hooker Blackheart engine perches (PN BHS511) were called into action. These bolt to the top of the frame rail and crossmember.
We cleaned and installed the ugly OEM intake manifold and treated the cooling system to a new water pump and 185°F thermostat before lowering it into the 50-year old engine bay. The mounts aligned perfectly to secure the 5.3L in a factory location with plenty of room for front accessories.
For the exhaust, we kept things simple and easy on the wallet with a set of Flowtech’s cast iron manifolds (PN 11730FLT). The manifolds tuck in towards the engine providing clearance for most any muscle car or truck chassis. They have a 2.25” outlet, we’ll never have to worry about a flange leak, plus they’re quieter than headers. To be honest, we tried the factory truck manifolds but both sides contacted the frame.
With the engine in place, it was time to bring the fuel delivery system up to LS standards. We went with a Holley Sniper Universal Pump Hanger (PN 19-350) so the new 340 LPH pump could be mounted in the tank. The kit features a low-profile cast ‘hat’ with three ¼” NPT outlets (feed, return and vent) and has a unique mounting design so it can easily be clocked for different applications.
The fuel pump needs to be installed so the sock is just touching or near the bottom of the tank. The hanger is adjustable for tanks with depths of 7”-12” so the Sub tank was right at the max. The pump is wrapped in a foam sleeve then secured with two clamps. Do not forget to plug-in the electrical connector!
With the thick foam gasket in place, the assembly was lowered into the 3.25” hole we cut. Make sure the mounts and fuel level sending unit will not interfere with the new assembly before drilling the hole. The mounting lugs will swing out and lock in place as the five screws are tightened using a crisscross pattern to 40-60 in-lbs. A Sniper EFI Fuel Hose Kit (526-10) includes 40’ of high pressure hose, a 10-micron filter and several fittings.
The new fuel hose was directed up the passenger frame rail. The 10-micron filter was installed about half way. Once the hoses were routed up to the engine, a pair of Earls fuel rail adapters were used to connect the new hose to the factory fuel rails. A 3/8” to -6 was used on the feed with a 5/16” to -6 on the return.
With the engine mounted and fuel system plumbed it was time to get into the electrical system, starting with mounting the Terminator X Max ECU. Since there was already a hole in the firewall for the harnesses, we opted to install the unit under the dash. One thing we didn’t take into consideration was this blocked the diagnostic LEDs that are on the top side of the unit. We may modify the mount down the road.
The first of five harnesses, was the main power/battery connection. This is a fused, two wire harness that simply connects to battery positive and ground. If possible, it is recommended to connect the wires away from other connections. Fortunately, our Optima battery has both side and top posts.
The main harness serves primarily as the inputs from the engine’s sensors plus has the coil connectors for each bank. Note that there are two ground wires, one for each cylinder head, that must be connected to supply a quality ground for the ignition. Don’t let the harness intimidate you as each connector is clearly marked, such as the Manifold Temp, Coolant Temp, TPS, IAC and Fuel shown.
There’s no good way to start other than heaving the harness onto the engine and begin routing the connectors. Holley designed the harness with plenty of length to reach the ECU and all of the sensor locations.
With the main harness in place, we connected the coil harness and the fuel injector harness. When you order the Terminator, you’ll be asked what injectors you will be using (EV1, EV6 or Multec 2). Our engine had the common EV6 style injectors and we used harness 558-201.
With the underhood connections handled, we moved under the dash to figure out the drive-by-wire connections. Holley offers two DBW harnesses to be used with a specific pedal and throttle body combination. Our engine was equipped with an 8-pin throttle body (GM PN 12570800) which requires Holley’s PN 558-429 harness as well as a GM throttle pedal assembly PN 10379038 (we forgot to take ours from the donor Tahoe). Surprisingly, the new pedal wasn’t too difficult to mount and the harness easily connected to the ECU, pedal and throttle body.
The last major electrical connections were to the transmission since the Terminator X Max has a built-in transmission controller. The harness has plenty of length and simply connects to the OEM round plug on the passenger side of the trans, along with the VSS. There is also a turbine speed connector which is only on a 4L80E trans.
Since our Suburban had been fitted with a 700-R4, the crossmember had already been moved with the exhaust worked around it nicely. We stuck with this crossmember though we really had our eyes on the new Hooker Blackheart crossmember (PN 71222024HKR-2). Once the trans was mounted, we needed to have the two-piece driveshaft shortened a little over an inch. An extra step, yes, but it was worth it as there was plenty of room up front for accessories and the mechanical clutch fan.
The 02 sensor was placed in our existing single 3” exhaust just after the Y-pipe. We liked the sound and routing of our Suburban’s exhaust or we would have gone with one of the Hooker Blackheart exhaust systems for C10s.
We were pleasantly surprised to see that our 1988 model year radiator fit back in place. Believe it or not, that mile long upper hose is a factory piece from the donor Tahoe. An extra bonus was being able to retain the shroud and factory clutch fan from the Tahoe as well. Sometime down the road we plan to upgrade to a direct-fit C10 LS swap Frostbite radiator (PN FB311) equipped with the inlet on the passenger side to shorten the hoses and clean up the cooling system.
A new Frostbite radiator is equipped to accept the LS steam vent hose but we got lucky with our old radiator as the heater outlet was threaded so a couple adapters were added to connect the steam vent.
With the wiring all connected to the ECU it was time to apply power for the first time. Also, a vacuum line was routed to the internal MAP sensor of the Terminator.
The handheld monitor walks you through the initial setup of the Terminator with a few standard questions about your new LS and application. One of the most important steps is a calibration test to confirm the DBW components are all functioning together. When everything was ready, we turned the key and the old LS fired right up and within a couple minutes had settled into a smooth idle. Once running, we switched to the multi-gauge screen to view a number of engine parameters as the LS started its second life – in a 50 year old C10!
You can’t say it looks original under the hood, but an LS sure fits nice in the engine compartment of any year C10. For now, we stuck the long, clumsy air intake assembly on since it fit but we plan to assemble a tight elbow and cleaner assembly soon. The engine swap itself went smoothly resulting in a professional looking installation. The same can be said for the advanced technology of the Terminator X Max and the fitment of their harnesses and connectors.
