11 RAREST GM ENGINES EVER PRODUCED
The General Motors that you know and love today looks nothing like the General Motors of yesteryear. In fact, GM didn't even originally deal in engines or cars, they dealt in horse-drawn buggies. Once gas-powered vehicles started to gain popularity and ease of production, GM followed suit by acquiring several pre-established motoring companies like Buick, Pontiac, and eventually, Chevrolet.
General Motors
General Motors is a US-based automotive giant, one of the "Big Three" automakers. Founded in 1908, GM owns iconic brands like Chevrolet, Buick, GMC, Cadillac, and others. Known for its diverse lineup, from affordable sedans to heavy-duty trucks, GM has a strong foothold in the global market.
From that point on, they were known to make some of the most iconic American vehicles of the 20th century, from the Chevrolet Bel Air to the Cadillac Eldorado. General Motors has also made some of the most iconic engines over the last hundred years or so.
We've covered big and small-block Chevrolet engines, Pontiac engines, and the like. Now, we're going to cover all of GM's engine repertoire and see which ones are the most rare. We're going to cover any engine, no matter the cylinder or displacement, and tell you how many units were made and what made them so special.
How we made our model selections: The engines below are ranked by production volume from most to least. The specifications table houses the engine's displacement, power, torque, and notable applications.
Ranking The Best GM Crate Engines
GM has been putting out great crate engines for decades, allowing enthusiasts to give their favorite builds a beating heart. Here are the best ones.
First Generation Oldsmobile 371 V8: 40,914 Units
First-Gen Oldsmobile 371 Specifications
| Displacement | 371 ci |
| Configuration | V8 |
| Power | 300 hp |
| Torque | 414 lb-ft |
| Notable Applications | 1957 Oldsmobile Super 88 |
| Units Made | 40,914 Units |
(Source: GM)
The first generation Oldsmobile V8 engine had four different displacement variations. The 371 cubic inch V8 was a standard V8 for Oldsmobiles at the time but is still rare by all accounts. Most notably, the 371 V8 could be found in the 1957 Oldsmobile Super 88.
It wasn't a perfect engine by any means and, in fact, had several failures, like the camshaft probably from an increase in displacement. The engines were problematic enough to discontinue them in the early 1960s. For the time, however, they did make an impressive 300 horsepower and 414 pound-feet of torque.
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Cadillac 500 V8: 26,000 Units
Cadillac 500 Specifications
| Displacement | 500 ci |
| Configuration | V8 |
| Power | 400 hp |
| Torque | 550 lb-ft |
| Notable Applications | 1975 Cadillac Eldorado |
| Units Made | 26,000 Units |
(Source: Hemmings)
Part of the 472 V8 generation, the Cadillac 500 V8 was a monstrous 8.2-liter V8 that outputted an equally monstrous 400 horsepower and 550 pound-feet of torque. The 500 V8 was only offered in the 1975 Cadillac Eldorado, while the engine itself was discontinued in the late 1970s.
The 500 V8 only offered 9.9 miles to the gallon in the Eldorado and got the old Cadillac up to speed in about 12 seconds. That might seem slow for such a high-powered engine, but the Eldorado's were enormous.
This 2009 Pontiac Is A Mouthful But There Are Only A Handful
Back in 2009, General Motors did something pretty spectacular using the Holden Commodore as a baseline, and gave the world the Pontiac G8 GT SLP Firehawks. Once you get past its rather long name, its incredible potency is the first thing that hits you. It was powered by a 6.0-liter supercharged V8 that made a cool 500 hp and 489 lb-ft of torque. Once you factor in that the Commodore had a rich touring-car racing heritage, it was easy to see that the G8 was more than just a straight-line monster. If all this sounds good, it should also be kept in mind that the G8 GT SLP Firehawk was also extremely limited-run. Only 27 examples ever saw the light of day, so the chances of running into one at your local used car dealership is pretty slim, to say the least. Still, though, would you consider buying one if the opportunity came along?
Chevrolet LT5 V8: 6,939 Units
Chevrolet LT5 Specifications
| Displacement | 378 ci |
| Configuration | Supercharged V8 |
| Power | 375 hp |
| Torque | 370 lb-ft |
| Notable Applications | Corvette ZR1 |
| Units Made | 6,939 Units |
(Source: Hemmings)
The LT5 is so special, in fact, that General Motors didn't even manufacture it themselves. They took to marine motor manufacturer MerCruiser because they had the most knowledge when it came to manufacturing all-aluminum block V8s. The LT5 V8 is a supercharged engine with 375 horsepower and 370 pound-feet of torque.
It was supposed to be the V8s to end all V8s and featured in the C4 Corvette special edition ZR1, but it just didn't happen that way, and ended up only making a couple of thousand units. Years later, it was rebranded in the form of a crate engine on a totally different platform and twice the horsepower.
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GMC 702 V12: 5,000 Units
GMC 702 Specifications
| Displacement | 702 ci |
| Configuration | V12 |
| Power | 420 hp |
| Torque | 630 lb-ft |
| Notable Applications | GMC Firetrucks |
| Units Made | 5,000 Units |
(Source: Hagerty)
Did you know that GMC used to make 12-cylinder engines? Not only were they big at 702 cubic inches, but they were also extremely heavy thanks to their cast iron body composition. Don't think of these engines as loud and proud supercar-adjacent engines.
Think of them more like an engine for a tug boat or, more realistically, a fire engine. You couldn't get that kind of speed with a 180-pound crankshaft even if you put a supercharger on it. It outputted 420 horsepower and 630 pound-feet of torque.
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Chevrolet LS9 V8: 4,684 Units
Chevrolet LS9 Specifications
| Displacement | 376 ci |
| Configuration | Supercharged V8 |
| Power | 638 hp |
| Torque | 604 lb-ft |
| Notable Applications | C6 Corvette ZR1 |
| Units Made | 4,684 Units |
(Source: Chevrolet)
The C6 Corvette ZR1 features the blisteringly quick, supercharged 6.2-liter LS9 V8 with 638 horsepower and 604 pound-feet of torque. This special edition V8 engine was made for the ZR1 Corvettes, a car that cost around $100,000 at the time.
This small-block engine could get the Corvette up to 60 miles per hour in just 3.4 seconds and 100 miles per hour in 7 seconds flat. Chevrolet refers to this engine as a "technological marvel" and in all respects, it is. It's also been sold as a crate engine, so if you want to, you could LS-swap your GMT800 Suburban.
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Cadillac V16: 4,076 Units
Cadillac V16 Specifications
| Displacement | 452 ci |
| Configuration | V16 |
| Power | 165 hp |
| Torque | 320 lb-ft |
| Notable Applications | 1938 Cadillac Series 90 |
| Units Made | 4,076 Units |
(Source: Hagerty)
You read that correctly, Cadillac, at one point, had a 16-cylinder engine in a V formation. What you're also reading correctly is that it only made 165 horsepower and 320 pound-feet of torque, which is painfully nothing for an engine of that size.
Cadillacs from the 1930s that use this engine are worth their weight in gold; and (according to Hemmings), they go for anywhere from $300,000 to $1 million. Cadillac tried to revive a V16 in a concept car recently, but it never saw production.
Chevrolet ZZ4 V8: 430 Units
Chevrolet ZZ4 Specifications
| Displacement | 350 ci |
| Configuration | V8 |
| Power | 355 hp |
| Torque | 405 lb-ft |
| Notable Applications | Crate Engine |
| Units Made | 430 Units |
(Source: Hemmings)
This crate engine had limited production numbers of 430 units and can be found in any number of restored hot rods and/or muscle cars from the 1930s up to the 1970s. Depending on what car they're found in, the vehicle sporting the engine can be valued anywhere from $20,000 all the way up to $55,000. The engine itself produces 355 horsepower and 405 pound-feet of torque.
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Pontiac Super Duty 421 V8: 150 Units
Pontiac Super Duty 421 Specifications
| Displacement | 421 ci |
| Configuration | V8 |
| Power | 405 hp |
| Torque | 425 lb-ft |
| Notable Applications | Pontiac Grand Prix, Pontiac Catilna 2+2 |
| Units Made | 150 Units |
(Source: Hemmings)
The 1950s were referred to as the "horsepower wars" with automakers at the time engaged in battle to find out who could make the most out of their big block engines. According to Hemmings, Pontiac was looking to shake things up in the automotive world by surpassing displacement at 421 cubic inches instead of just 400.
That added displacement gave their engines 405 horsepower and 425 pound-feet of torque. For the most part, they were featured in racing vehicles, but they were also featured (predominantly) in the Pontiac Catalina.
Chevrolet L88 V8: 216 Units
Chevrolet L88 Specifications
| Displacement | 427 ci |
| Configuration | V8 |
| Power | 550 hp |
| Torque | 470 lb-ft |
| Notable Applications | Stingray Corvette |
| Units Made | 216 Units |
(Source: Supercars.net)
This Chevrolet Corvette L88 engine is, according to Robb Report, the "Holy Grail of Corvettes." The specific one that they mentioned in the article was being sold for close to $4 million. Rightfully so, since they only made 216 units of this engine for the Corvette Stingray, so who knows how many of these original small block V8s are actually left. For the time, they were particularly fast too, with 550 horsepower and 470 pound-feet of torque.
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Chevrolet 427 Z11 V8: 57 Units
Chevrolet 427 Z11 Specifications
| Displacement | 427 ci |
| Configuration | V8 |
| Power | 430 hp |
| Torque | 575 lb-ft |
| Notable Applications | Impala Z11 |
| Units Made | 57 Units |
(Source: Bring a Trailer)
The Impala on Hemming's website has a sticker on the side that says "Old Reliable." It could also be called "Old Faithful' as this 427 cubic inch motor faithfully pushes out 430 horsepower and 575 pound-feet of torque.
It's most notably tied to an Impala race car from 1963 and was only produced in 57 separate units. This specific engine was part of the "horsepower wars" from the 50s that seeped into the 60s and was meant to compete with the Fords and Pontiacs of the day.
The Story Behind The 1963 Chevrolet Impala Z11 Package
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Oldsmobile W43 455 V8: 6 Units
Oldsmobile W43 455 Specifications
| Displacement | 455 ci |
| Configuration | V8 |
| Power | 440 hp |
| Torque | 500 lb-ft |
| Notable Applications | Delta 88, Oldsmobile Cutlass |
| Units Made | 6 Units |
(Source: Hemmings)
The W43 455 was quite literally an experiment. Oldsmobile was doing everything within its wheelhouse to try and beat out the HEMI V8 by adding two more valves to each cylinder, equating to a total of 32. Oldsmobile didn't bring this engine into production, but when they tested it, the mill delivered 440 horsepower and 500 pound-feet of torque. They only made six, which makes this the rarest engine ever built by GM.
Sources: Hemmings, Hagerty, Bring a Trailer, New Cadillac Database, Supercars.net, S10 Forum, Robb Report, Mecum, GM, Corvette Blogger, XtremeCFM
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