In the time-honored fashion of car crafters since the first days of hot rodding, gearheads have taken the latest engines and stuffed them into earlier, lighter, and more affordable cars all in the name of going fast. Your grandfather stuffed flathead V-8s in Model A roadsters, but for the latest generation of enthusiasts, it's the Gen III engines that are the new darlings of the GM engine swap set.
The Gen III began its production run with the new '97 C5 Corvette and was quickly followed in the Camaro and Firebird. These LS1 and later LS6 engines are all-alloy-light and make outstanding power based on excellent cylinder head architecture, and they feature a distributorless coil-near-plug ignition that, while electronically complex, also offers the potential to set the engine farther back in the chassis since you don't have to access a distributor!
Less well known but just as important is the fact that all fullsize GM trucks built since 1999 also utilize the Gen III configuration in an interesting series of displacements that mirror its first-generation small-block heritage. The GM truck/SUV Powertrain lineup includes a range of engines displacing 4.8L, 5.3L, and 6.0L. The 4.8L and 5.3L engines displace 293 ci and 325 ci respectively, while the 6.0L pencils out to 364 ci. If you think of the 4.8 as a large 283 and the 5.3 as a small-bore 327, and the 6.0L as a mild stroker 350ci, then you're right on target.
SimilaritiesAll these Gen III engines are based on the same 4.400-inch bore centers and deck heights along with main, rod, and cam bearing journals. All the heads interchange, as do cams, valvetrain, intakes, oil pans, valve covers, and accessory drives. This makes mixing and matching parts from boneyard engines easy, but care needs to be taken to match the pieces properly. The truck engines all utilize iron blocks with aluminum heads-only the '99 LQ4 6.0L engine came with iron heads. The only exception to this is the current '04 SSR truck 5.3L engine that employs an aluminum block and heads to trim a little fat in the portly pickup.
This similarity between the engines makes especially the truck powerplants attractive for engine swappers. The hot ticket if you're looking for a bigger-inch engine would be the LQ4 and LQ9 truck, Cadillac Escalade, and EXT engines. These 364ci engines would be perfect fodder for an early Camaro/Chevelle engine swap if you don't mind the extra weight of the iron block. The advantage is that these engines will probably be less expensive than the all-alloy Corvette or Camaro/Firebird LS1/LS6 engines. The weight difference is roughly 100 pounds.
DifferencesWhile the basic engines are the same, each application varies wildly in terms of intake manifolds, water pumps, front accessory drives, and oil pans. The Corvette engines have the best and shallowest oil pan for pulling lateral g's, but it's also the most difficult to fit into an earlier musclecar. The F-car rear-sump pan is 511/44 inches deep and offers the most potential, but even it will usually require surgery. We've run across a total of five different oil pans with two variations on rear-sump truck pans with the C/K truck pans measuring 811/42 inches deep.
There are at least three distinctly different accessory drives, and the photos illustrate the basic differences between the Corvette, F-car, and truck systems. The water pump also changes between the cars and trucks, and there are several variations on the exhaust manifolds between the Corvette, Camaro, and trucks. The accessory drives not only vary by positions of the pumps and alternators but also by the depth of these systems. The Corvette tucks the drive pulleys closest to the front of the engine, with F-car next, and the trucks placing them the farthest forward of the three. Keep this in mind if you're considering mixing and matching pieces within these accessory drives. That could be a nightmare.
Swap TricksCompanies like Street & Performance jumped on the Gen III swap wagon early, and the company offers modified oil pans, accessory drives, and other pieces necessary to make your engine swap plans more successful. Painless Wiring and Howell Engine Developments offer wiring harnesses that simplify the swap using the factory computer, while ACCEL/DFI, Big Stuff's, FAST, and Electromotive to name a few now offer the ease of spark and fuel tuning for a serious effort engine swap. Headers and exhaust are the next big areas of development, and we expect to see companies like Hedman and Hooker offering engine swap headers for Gen III engines relatively soon. Hedman already offers a 151/48-inch primary pipe block-hugger header for the Gen III.
Power Potential The Gen III engines are already making a mark in the performance world with plenty of examples of stock 5.7L engines equipped with a mild cam and a good intake like a GMPP LS intake or the new LSX intake from FAST where these engines are making right around 470 to 475 hp. Add a set of CNC-ported heads from one of several companies like Lingenfelter Performance Engineering (LPE) and 500 hp is almost commonplace.
Want to talk stroker packages? Lunati, for one, offers crank and rod packages for the 5.7 to build 383-to-408ci packages that can add serious power and durability with strong 4340 steel cranks and rods. There are also carbureted intake manifolds available now from Edelbrock that allow you to run a carburetor on a Gen III and still use the coil-near-plug ignition with a conversion box. Finally, GM Performance Parts is close to releasing a carbureted intake manifold and a front cover that will mount a distributor to light the plugs. As you can see, in the coming months, the Gen III will be well covered in performance parts.
ConclusionAs the truck Vortec engines, the new GTO, Corvette, and now even the Cadillac CTS-V all come with Gen III and soon to be Gen IV engines, this latest branch in the GM Powertrain tree has already blossomed with several power-producing opportunities. All you have to do is decide which engine will be the focus of your next grand adventure. Take it to the streets, baby.
By the Numbers Liters Cubic Inches Bore/Stroke Comp. Rod Int. Exh. Ratio Length Valve Valve 4.8 293 3.{{{780}}}/3.268 9.5 6.276 1.890 1.551 5.3 325 3.780/3.622 9.5 6.098 1.890 1.551 5.7 346 3.898/3.622 9.5 6.098 2.000 1.551 5.7 346 3.898/3.622 10.1 6.098 2.000 1.551 6.0 364 4.000/3.622 9.4 6.098 2.000 1.551 6.0 364 4.000/3.622 10.0 6.098 2.000 1.551Power CurvesThe power numbers listed here are only a fraction of all the different power levels. We've chosen to illustrate the range by showing early numbers followed by the most recent '04 power levels. Note for example that the '04 Corvette LS1 now makes almost 15 percent more horsepower than it did in the '98 Camaro.
Engine Horsepower Torque Application LR4, 4.8L 255 @ 5,{{{200}}} 285 @ 4,000 '99 Truck 270 @ 5,200 285 @ 4,000 285 @ 5,200 295 @ 4,000 '04 Truck LM7, 5.3L 265 @ 5,000 320 @ 4,000 '99 Truck 285 @ 5,200 325 @ 4,000 295 @ 5,200 330 @ 4,000 '04 Truck {{{SSR}}} 5.3L {{{300}}} @ 5,200 330 @ 4,000 SSR {{{Pickup}}} LS1, 5.7L 305 @ 5,200 335 @ 4,000 '98-'99 {{{Camaro}}} 350 @ 5,200 375 @ 4,000* '04 {{{Corvette}}} LS6, 5.7L 385 @ 6,000 385 @ 4,800 '01 Corvette 400 @ 6,000 400 @ 4,800 '04 Corvette LQ4, 6.0L 300 @ 4,800 360 @ 4,000 '01 Truck 325 @ 4,400 365 @ 4,000 '04 Truck LQ9, 6.0L 345 @ 5,200 380 @ 4,000 '04 SS Truck * Manual trans only—automatic-backed LS1s make less torque