How to Swap in a Carb-Equipped LS Engine

Carb-Equipped LS Swap 101 - Want modern LS power but without the hassles of retrofitting fuel injection? We show you how.

Patrick Hill Jan 28, 2014 0 Comment(s)
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Since it came out in 1997, the LS engine family has altered the landscape of Chevrolet performance almost as much as Gen I series small-block. It’s a great performer in modern vehicles, but its compact dimensions and huge power make it a prime choice for being swapped into earlier Chevrolets. While the Gen I family still reigns supreme for overall cost effectiveness, its offspring (Gen III and IV) are quickly closing that gap.

One thing that still gives some trepidations about performing an LS swap into an older vehicle is fuel injection. All the wiring, fuel line plumbing, mounting a computer, etc., is still a daunting task for many when compared to bolting on a simple carburetor that you only need a screwdriver and vacuum gauge to tune. Many enthusiasts tend to stick with what they know, and a lot of guys know carbs better than they know their own cell number.

But what about putting a carb on an LS engine? Many on both sides would decry it as sheer lunacy. The fuel injection side would scream “Why are you putting archaic technology on a modern engine?”, while the carb side would yell “That’s too complicated!”

So, why convert an LS engine to a carb for an engine swap? Greg Lovell, owner of Antivenom High Performance in Seffner, Florida, is one of the country’s leading tech’s for swapping LS engines into cars. We asked him why would you do this.

“A swap like this can be done to save on the expense of wiring, elaborate fuel systems, computer tuning availability, and simply as a starting point. The swap can be driven this way for a long time,” says Greg. “Later, a fuel system and computer controls can be added for the full swap. A carb equipped LS engine is a very easy way for an old-school Chevy guy to get familiar with the Gen III and IV engine family, and not have to learn the computer tuning. He can now simply get his feet wet as opposed to diving right in.”

As it happened, Greg had an ’87 Caprice at his shop that was undergoing a salvage yard 5.3L truck engine swap and the owner wanted carburetion. Thanks to a new array of parts from Holley and its subsidiary companies, swapping in a carb-equipped LS is easier than ever. We decided to follow along, and see exactly what goes into doing this swap. It was pretty eye opening, and once you read through, it might make you reconsider your next build.

1987 Caprice Stock 305 2/39

1. Here’s where we started. The 305 in our subject ’87 Caprice had over 200k miles on it, was never much in the power department, and had begun consuming oil, smoking, and was just ready for retirement.

Hooker LS Swap Motor 3/39

2. Since LS engines use a different motor mount location, adapter plates have to be used when installing in a pre-LS factory chassis. Hooker’s adapter plate (part no. 12611HKR) bolts right to any LS block, and allows for the use of earlier factory motor mounts and mounting locations.

L33 5 3L LSx Truck Engine  2004 Trailblazer 4/39

3. This salvage 5.3L engine came from an ’04 Chevy Trailblazer. For $600 on eBay, the car’s owner got a running, all-aluminum 5.3L, a real catch. Unfortunately, the factory oil pan on the 5.3L won’t work when retrofitting this engine into an earlier vehicle. Because LS engines use a gerotor-design oil pump that’s driven off the crankshaft, the oil sump pickup is located at the front of the engine.

Holley LS Swap Oil 5/39

4. The solution is Holley’s retrofit oil pan, part no. 302-1. It comes complete with oil pickup tube and baffle, and allows for a wet sump LS engine to clear earlier factory crossmembers and steering linkages.

Holley LS Swap Oil Pan 6/39

5. The oil pan kit comes with a new pickup that shifts the sump to the rear of the oil pan.

Holley LS Swap Oil Pan 7/39

6. This baffle plate is included to prevent oil sloth and frothing, keeping the pickup immersed in oil.

Holley LS Swap Oil Pan 8/39

7. The Holley oil pan uses a rear sump design like Gen I small-blocks and Mark IV big-blocks, so it’ll clear factory steering systems without problems (except ’62-’67 Novas). It’s a solid cast aluminum piece, so durability and strength are no question here.

1987 Caprice 305 V8 Engine 9/39

8. Out comes the 305. For less than the cost of rebuilding this engine or buying an already rebuilt 305, the owner picked up a 290 horsepower 5.3 out of wrecked Trailblazer via eBay. Yes, there is the cost of the conversion parts, but in the end, this engine will last another 200k miles (with regular maintenance, provide almost twice the horsepower and better fuel economy. Because it’s all aluminum, it takes 150 lbs off the nose of the car.

1987 Caprice LS Swap Motor 10/39

9. The upper mount bracket from the 305 is bolted onto the Hooker adapter brackets.

1987 Caprice LS Swap Torque Converter 11/39

10. When bolting an earlier transmission to an LS engine, there’s a problem—the torque converter. The flange on an LS is a different thickness than on a Gen I motor, and it doesn’t align the Gen I torque converter properly.

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