LS Engine Swap - Modern Muscle

An LS Swap can Infuse New Life into Classic Muscle

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In the hot rod world engine swaps are a big part of what we do. It can be a small-block V-8 to replace a straight six-banger, a big-block in place of a small-block, or any number of "this for that" combinations. These days one of the more popular gyrations is to drop a modern EFI-fed, computer-controlled mill underhood, and the most popular choice is GM's line of LS engines. After all, what's not to love? Great street manners, lightweight aluminum goodness, killer gas mileage, and a rock-solid EFI system wrapped up in an arguably affordable package.

But, swapping in an LS engine isn't exactly a straightforward endeavor. The LS mill has needs that differ from a carburetor-fed Gen-I small-block. There are also mounting details that need to be addressed. The early swaps were pretty challenging, especially when it came to dealing with wiring harnesses and computer programming. Today these challenges are easily overcome by a host of companies churning out parts to make swapping in an LS engine nearly painless. And while this install deals with a Chevelle, the principles apply to any Chevy you might feel needs a little mechanical modernization.

A great way to shave a few pounds and add a bunch of reliable power is to drop in a 6.2L (that’s 376 ci for those who shun the metric system) LS3. A typical LS3 is rated at 430 hp, but this example is an LS376 engine from Chevrolet Performance. With its more aggressive bumpstick it churns out 480 hp. At a street price of just over $6,500 it’s not cheap, but, when you consider it's an all-aluminum EFI small-block then it's certainly a great bang-for-the-buck.

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Backing up our LS376 is a Tremec T56 Magnum from Hurst Driveline Conversions (HDC). With triple-cone synchronizers on gears one through four and doubles on the rest, including reverse, it shifts like butter. The Magnums can be ordered in different ratios and we chose the version with a 2.66 First gear and 0.63 Sixth gear. All Magnums share a 26-spline input and stout 31-spline output shaft. HDC offers basic kits starting at $2,995, but we opted for their Elite Kit, which was $4,295. Hey, what’s cooler than a wagon with a manual transmission? The answer is, "not much".

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The Best of Show crew then lowered the LS376 crate engine into the Chevelle’s cavernous engine bay.

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Getting an LS engine into a classic Chevy, or any car for that matter, requires the right oil pan. This task is even more challenging on a Chevelle due to interference with the steering linkage at full lock. One of the most compact oil pans out there is this steel 5.5-quart oil pan from Autokraft ($400). It features a four-corner trap-door baffling system and a thick steel flange that’s less likely to warp and leak. It came to us with a billet oil filter adapter, which we used to make life easier, but they also offer an adapter if you want to run a remote oil filter and cooler arrangement.

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To accommodate the large T56 Magnum six-speed trans, it was necessary to enlarge the trans tunnel quite a bit.

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Mating the new-school engine to the old-school frame mounts used to be a pain, but today it's as easy as calling up Holley and ordering up a set of their billet engine plates. This let us bolt on a urethane motor mount kit from Energy Suspension (PN 31114.G, $40) that would work with the factory frame mounts. Keep in mind that engine plates from different companies place the engine in slightly different locations, which can effect transmission placement and header fitment. So do your homework before ordering.

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Here you can see the Magnum installed under the Chevelle. The Hooker headers hugged the floor nicely for added ground clearance.

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The clutch actuation parts aren't included in the Elite kit since one can either go mechanical or hydraulic. The mechanical kit runs $350 and the hydraulic kit is a bit more, at $595. Because it's easy to install, compact, and, in our opinion, simpler to deal with, we went hydraulic. The kit came with a GM throw-out bearing, “short”-style Tilton master, billet firewall mounting bracket, remote reservoirs, and a bunch of fittings. The firewall bracket is especially nice since it seals the required hole in the firewall and is much stronger than the angled steel plate brackets we've used in the past. The kit also included all the various bits needed for installation. Having these parts, especially the electrical pigtails, included sure beats running around town trying to source them.

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You can spend as much or as little on pulleys as you want. In this case we just wanted something functional and reliable and this kit from Chevrolet Performance fit the bill perfectly. The kit (PN 19155067, $800) included a 150-amp alternator, power steering pump, V-7 variable displacement A/C compressor along with all the brackets, tensioners, and belts needed. Since we’re not running A/C we went with a kit that omits this (PN 19155167, $699). We should note that the low mounting of the A/C compressor wouldn’t work in most applications without frame modifications and the GM compressor isn’t compatible with most aftermarket A/C systems.

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The Hurst Driveline Conversions installation kit included this Luk HD Pro Gold clutch kit (PN 04-905). It's pretty much a factory replacement for the LS7 Z06 Corvette, so it should serve the wagon well.

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To prep the Magnum for installation we bolted on the GM clutch master supplied in the kit. As a bonus, it came pre-bled.

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We splurged a bit and went with a Quick Time SFI-certified spun-steel bellhousing (PN 8020), which came in at a relatively svelte 20 pounds. In addition to being super strong we’ve found them to very accurate dimensionally. Trust us that an out-of-shape bell is nothing but headaches down the line. If you want to save some cash then HDC also offers an aluminum GM bellhousing.

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