LS Engine Swap - Modern Muscle

An LS Swap can Infuse New Life into Classic Muscle

And here's our pulley system all installed and looking good. If you're on a super-tight budget you could source something like this from a bone yard, but we feel the convenience of having all the bolts, nuts, and widgets along with the sparkly new parts is worth the asking price.

1303 Chpp 14 O LS Engine Swap Chevrolet Performance Pulley 2/30

It’s easy to overcomplicate a fuel system, but this one is simple. Fuel from the tank enters the 10-micron filter (PN 162-554, $74) on the left and is pulled through the pump before going to the bypass regulator (PN 12-846, $145). The return off the bottom of the regulator sends the unneeded fuel back to the gas tank. The pump (PN 12-700, $259) is Holley’s new high-volume billet in-line deal, which is rated up to 700 hp in EFI applications.

1303 Chpp 20 O LS Engine Swap Holley Fuel 3/30

Going to an LS means you also need to run a cooling system with electric fans. Again, you can spend a little or a lot on this, but we found a great bargain to be the aluminum radiators offered by Summit Racing. The dual-row, crossflow radiator (PN SUM-380457, $300) fit the Chevelle perfectly and the dual 12-inch fans (PN SUM-G4850, $210) move 2,600 cfm to keep our LS376 running cool.

1303 Chpp 24 O LS Engine Swap Summit Racing 4/30

Even the once complex task of wiring up an LS engine is now a plug-and-play deal, especially if you're using a Chevrolet Performance crate engine. This kit (PN 19258267, $1,080) includes the controller, engine harness, mass airflow meter, fuse box, throttle-by-wire pedal assembly, oxygen sensors, and sensor mounting bosses. The computer came pre-programmed to run the LS376.

1303 Chpp 15 O LS Engine Swap Chevrolet Performance Wiring 5/30

We used this trick Aeromotive fitting (PN 15118, $38) to change our factory quick-connect fitting into an easier to integrate -AN style. In this case, it was from 3/8-inch quick connect to AN-08. Our fuel line is AN-06 so we used some fittings from Earl’s Performance Plumbing to connect it to the black braided fuel line coming from our regulator. We were also careful to route the fuel line away from heat sources, like the headers and exhaust.

1303 Chpp 21 O LS Engine Swap Aeromotive 6/30

Of course you’re not going to be able go down to the local auto parts store and ask for ’71 Chevelle LS1 radiator hoses, but the good news is that if you dig around long enough you’ll find something close enough. In this case NAPA had upper (PN 8919) and lower (PN 708) hoses that fit perfectly. For an air induction system, Spectre Performance sent us an LS air intake kit made for our Chevelle (PN 901208K, $200).

1303 Chpp 25 O LS Engine Swap Radiator 7/30

It’s the simple things that typically end up being the most difficult to address. In this case it’s trying to get the wiring harness from the engine bay into the car’s interior. We found the best grommet for doing this over at Speartech Performance where in addition to making killer wiring harnesses they also offer specialized LS swap widgets.

1303 Chpp 16 O LS Engine Swap Wiring 8/30

After pulling the power brake booster, which wasn’t working anyway, we installed the billet clutch master bracket from HDC. With this in place, we were able to mark the firewall and make the hole for the Tilton clutch master.

1303 Chpp 22 O LS Engine Swap Clutch Master 9/30

Headers are another area that used to be a pain, but are now relatively simple. Quite a few companies bend up pipes for various Chevys, but we thought we would try out the new ceramic-coated Super Comp headers from Hooker. These 1.75-inch mandrel-bent conversion long-tube headers (PN 2289-1HKR, $680) have 5/16-inch flanges for a better seal, and long-transition collectors to decrease backpressure. Best of all they are designed to fit when used with Holley LS engine mount adapter plates. The GM plug wires that came with the crate engine wouldn’t clear the headers, so we installed some MSD wires (PN 32813, $66) with angled boots.

1303 Chpp 26 O LS Engine Swap Super Comp 10/30

Installing the wiring harness was a snap due to all the connectors being clearly labeled. We then continued plugging in all the various wires to the throttle body, MAP sensor, fuel injectors, and coils. It really couldn’t be any easier. We did find that the wiring kit called for a different oil pressure sensor (PN 12616646, $73), so we had to buy one at the local GM dealership.

1303 Chpp 17 O LS Engine Swap Wiring Harness 11/30

After installing the clutch master, and attaching it to the new clutch pedal, we installed a new power brake booster from Classic Performance Products (CPP). You can see the clutch reservoir mounted to the firewall behind the booster.

1303 Chpp 23 O LS Engine Swap Classic Performance Products Power Brake 12/30

Once we had the engine and transmission installed we could measure back from the tip of the T56’s output shaft to the middle of the U-joint on the Currie Enterprises 9-inch rearend. Hurst Driveline Conversions was then able to send us the appropriate driveshaft. You can also see where we mounted the Holley fuel system.

1303 Chpp 27 O LS Engine Swap Output 13/30

Included with the harness is an OE-style fuse box and all the fuses and relays needed to fire up the LS3. Even more importantly, there was a detailed instruction manual for those of us who are electrically challenged. The fuse box can be mounted in the engine bay or, as we chose, under the dash.

1303 Chpp 18 O LS Engine Swap Fuse 14/30

The cool thing about a wagon is that it’s not very common. The pain about owning a wagon is that it’s not very common. To complete the exhaust system, we picked up a Flowmaster stainless Chevelle kit (PN 817409, $543) and let the guys at Warner’s Muffler in Oceanside, California, custom tweak it under our wagon. The system is centered around a pair of sweet-sounding Super 40 stainless mufflers.

1303 Chpp 28 O LS Engine Swap Chevelle 15/30

Moving into the interior we mounted the throttle-by-wire gas pedal (PN 10379038). To get the placement just right we welded a panel to the firewall and then mounted the pedal in just the right spot to make heel-toe shifting easy. We also swapped in the new brake and clutch pedal assembly from Ground Up (PN FC-682, $100).

1303 Chpp 19 O LS Engine Swap Throttle By Wire Gas 16/30

And with that, our swap was done. In fact when we turned the key it fired up on the first try! Since the hood was off we added a pair of Eddie Motorsports billet hood hinges (PN EMS149-57M, $550). The old battery wasn’t holding a charge, so we installed an Optima Yellowtop battery. The only thing left to do now is hit the road in our LS-powered Chevelle.

1303 Chpp 29 O LS Engine Swap LS3 17/30


Summit Racing
Akron, OH
Lenexa, KS 66214
Eddie Motorsports
Rancho Cucamonga, CA 91730
Warner's Muffler
n/a, CA
Spectre Performance
Ontario, CA 90761
Chevrolet Performance
Ground Up
Quick Time
Optima Batteries
Milwaukee, WI 53209


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