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GM vs Mopar vs Ford – Which Had The Hottest Muscle Car Small Block

When it comes to Classic Muscle Cars, much of the attention goes to 426 Hemis, 454s, and 427s. Here we pick the best of the Muscle Car small block motors.

A couple of quick ground rules (and we’ll know if you’re paying attention by your Facebook comments). First, we’re selecting engines that were available between ’64 and ’72 – the Classic Muscle Car era pre-smog controls. Second, we considered only engines using carburetors, as otherwise it provided the very small number of fuel injected engines an unfair advantage, and also skewed our comparison.

Also, as there’s no way to verify claims about overrating or underrating engines, we’re going to assume all manufacturers were playing the same game and use the horsepower figures they stated at the time.

And finally, remember this is a list of small blocks, so no Ford FE, any GM Big Block, or Chrysler B or RB motors.

Also, at the very end there’s a chart that lists each each and the horsepower it generated per cubic inch, as the difference between the smallest and largest engines is almost 1 liter in displacement (Ford has cars driving around with 1 liter engines, so it’s significant).



Ford Q-Code Cobra Jet – 280 hp

The 351 Cleveland was introduced in 1969 for the 1970 model year.  A 4V (four-barrel carburetor) performance version and a 2V (two-barrel carburetor) version were built. The 351C four barrel was marketed as a high performance engine, featuring large valves, ports and a closed “quench” combustion chamber. Only the Q-code 351 “Cobra Jet” (1971–1974), R-code “Boss” 351 (1971), and R-code 351 “HO” (1972) versions have 4-bolt mains bearing caps.



Ford Boss 302 – 280 hp

The Ford Boss 302 was built for one purpose – to win the Trans-Am Championship against Camaro, Challenger, Barracuda, and Javelin. The small block V8 motor was created by mating the heads from the yet-to-be-introduced Ford Cleveland V8 to the a 4 bolt heavy duty block of the Ford Windsor. The heads are “tunnel-port” where the pushrod runs a straight path through brass tunnel in the intake runner allowing for better airflow, a design adopted from the 427 FE. Atop a taller, higher manifold was fixed a four-barrel carb. In stock form it produced 290 HP in “net” trim, only 60 hp less than the Hemi that’s 30% larger.



Chevrolet Z/28 302 – 280 hp

Like the Ford Boss 302, this motor was developed to win the SCCA Trans Am Championship. The engine was created by (basically) installing a 283 crankshaft into a 327 block to create a motor with a four-inch bore and a three-inch stroke displacing 302 cubic inches, just under the 5.0L class limit. The focus of the Camaro Z/28 motor was not really torque, but of being able to run at high revs, as Trans Am races began with rolling starts and most turns at the tracks of that time were mid- to high-speed corners. To develop this motor, Chevy engineers applied all the hardware originally designed for the larger L76 327 (which shared its bore) , including high-flow, big valve 461 cylinder heads, a solid lifter 30-30 camshaft, shot-peened rods, and a high-rise aluminum intake topped with a Holley 780 four-barrel carburetor.



Ford 351 Windsor – 290 hp

Ford debuted the 351 Windsor in the 1969 Ford Mustang Mach 1 with both two-barrel  and four-barrel carburetor options. The 290 hp  four-barrel version was dropped after a single model year. By 1978, in an effort to meet emissions regulations Ford began installing small-valve 302 cylinder heads on the 351W. There is a happy ending to the story.  It was resurrected as the performance motor for later model Mustangs, though known by its “metric” name – the Ford 5.8L. At which point enthusiasts started to clamor for go-fast parts and the automotive aftermarket responded. It last appeared in the 1995 Cobra R.



Chrysler 340 Six Pack – 290 hp

Much like the Ford Boss 302 the Chrysler 340 was designed with performance as the prime directive. Check this out: 10.5:1 compression, high flow heads with big valves (2.02 intake, 1.60 exhaust), forged and shot-peened steel crankshaft and connecting rods, topped with three two-barrel Holley carburetors.



Ford M-Code 351 Cleveland – 300 hp

The M-code was a high compression, high-performance variation of the 351 Cleveland, produced only in ’70 and ’71. The M-code engines used the large port/large valve 4V heads with a closed “quench” combustion chamber. These engines featured cast aluminum flat top pistons, stiffer valve springs, a high performance hydraulic camshaft, and a squarebore Autolite 4300-A carburetor. The ’70 engines had a 11.0:1 compression ratio and produced 300 hp on premium gas, while ’71 versions had a slightly lower compression ratio of 10.7:1 and produced 285 hp.



Shelby GT350 289 – 306 hp

The Shelby motor started with the Ford HiPo 289, which was engineered to increase performance and high-RPM reliability. It had solid lifters with hotter cam timing, 10.5:1 compression, a dual point, centrifugal advance distributor, smaller combustion chamber heads with cast spring cups and screw-in studs, low restriction exhaust manifolds, and a larger, manual choke 595 CFM carburetor. For the GT 350 Shelby would replace the cast iron exhaust manifold with tubular Tri-Y headers and replace the OEM carb and manifold with a larger Holley 715-cfm carburetor and a better flowing aluminum high-rise intake manifold. The improved top-end breathing pushed the Shelby motor to 306 hp in 1967, a 35 hp increase.



Pontiac 350 HO – 330 hp

In 1968 the Pontiac 326 V8 was replaced by Pontiac’s 350, which shared nothing with the Chevy 350. In fact, the Pontiac actually displaced 355 CID (5.8 L) although Pontiac decided to (or were instructed to) name it a 350. For the first year an HO option was available in the Tempest, and Firebirds that was rated at 320 hp. This engine was upgraded with cylinder heads and camshaft from the Pontiac 400 HO, raising the output of the 350 HO motor to 330 hp.



1971 R-Code Boss 351 – 330 hp

The Boss 351 R-code V-8 was among the last of the true Muscle Car engines, and was built accordingly:  hardened crankshaft with four-bolt mains, forged connecting rods that were shot-peened for strength and Magnafluxed for cracks, and held to the crank by exceptionally strong 3/8-inch bolts.  The free-flowing 4V heads were nearly identical to those used on the earlier Boss 302. High flow intake passages led to large valves allowing  the engine breathe and rev freely, thanks to a heavily-beefed up valvetrain. The R-Code produced  330 hp was know for its ability to outgun a number of big-blocks with  6.6 second runs 0-60.



Chevrolet L-79 327 – 350 hp

The 1969 L-79 Chevrolet small block was among the first and most popular applications of a hydraulic cam in Muscle car engine. The L79 was essentially the solid-lifter L76 (365 hp 327) with a cam swap. The two engines shared the same compression, big-valve heads and aluminum intake. The difference was the ability of the hydraulic cam to “keep up” with engine revs as they rose (and it continues to be an issue today – look at the specs for most modern multi-valve engines and you’ll find the camshaft has a direct action on the valves). That aside, the hydraulic cam offered a number of advantages, including quiet running and requiring no periodic adjustment.



Chevrolet LT-1 350 – 360 hp

In ’70 the LT1 350 engine was rated at 360hp in the Z28.  The first LT1 small-block was the only engine available standard in the Z/28 from ’70 through ’72. This small-block featured solid lifters,  a 780 CFM Holley carburetor on an aluminum intake manifold, a ‘178’ high-performance camshaft, and big 2.02 heads. For ’70 these engines had 11:1 compression, but dropped significantly for ’71 and ’72. The “LT1” designation was later reused on a Generation II GM MPFI “350” small block engine in late 1991, the LT1.




A summary of the comparison of the 11 small block high performance from the Classic Muscle Car era is included below. You’ll note that only three engines, the Chevrolet L-79 and LT-1 and the Shelby GT350 motor rated above 1 hp per CID. Others were close, to be sure. The Pontiac 350 (355) was particularly noteworthy, as it’s often passed-over by builders for a small block Chevy. The two engines developed for Trans-Am competition, the Z/28 302 and the 302 ranked equally at almost 1 hp per CID. Of course, you need to take all manufacturer ratings with a grain of salt – our comparison is based on all three using the same math to come up with their ratings.




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Chris Riley
About Chris Riley

I have been wrecking cars for as long as I've been driving them but I keep coming back for more. Two wheels or four, I'm all in. gives me a chance to give something back to the automobile community.

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