L79 327 vs L46 350

Words: Richard Holdener

Though small-block Chevy fans all share a common interest, that doesn’t mean they all agree on their favorite. Ask any group of Chevy fans about the best factory small block ever made and watch the feathers fly. Truth be told, Chevy offered a number of great mouse motors, the most powerful being the 370-hp LT1 350 and the 375-hp L84 (Fuelie) 327, also available as carbureted, 365-hp L76.

While the solid-lifter small blocks ruled the roost in terms of rated power output, Chevy also offered a number of different small blocks equipped with hydraulic lifter cams. The two hottest hydraulic small blocks ever offered included the 350-hp L79 327 and the like-rated L46 350. The simple fact Chevy offered two different (displacement) 350-hp small blocks means there were (and continue to be) lines drawn in the sand between the fans of each. The 327 guys cite the snappy rpm potential of the shorter stroke, while the 350 guys counter with the simple notion that bigger is always better (just ask the big block guys, right?). In reality, the best way to show what each small block had to offer was to build them and plop them on the dyno.

We know the dyno never lies, but before getting to the results, a little background might be in order for those unfamiliar with muscle-car mouse motors. Both the L79 327 and L46 350 were essentially hydraulic-lifter versions of their solid-lifter cousins. In the case of the smaller 327, the L79 was essentially a solid-lifter L76 (365-hp 327) with a cam swap. These two mouse motors shared the small-chamber, big-valve (fuelie) heads and aluminum high-rise intake. The 11.0:1 L79 also relied on a performance Holley four-barrel carb (both 585 and 600 cfm versions).

Because each engine was new prior to testing, the cam and lifters were treated to liberal coating of moly-based assembly lube, high-zinc break-in lube, and extended pre oiling.

The larger 350 L46 was not simply an L79 upgraded with increased displacement. In addition to the extra 13 cubic inches, the L46 featured revised cam timing (slightly increased lift and duration) and a completely different induction system. The high-rise, aluminum intake and 585-cfm Holley carb were replaced by a cast-iron, low-rise (for Vette hood clearance) intake and Rochester Q-Jet carburetor. While high-performance small blocks usually received a Holley, the Q-Jet used on the L46 actually out-flowed the Holley used on the L79 327.

In order to test the pair of small blocks, we first had to build them. As you might imagine, building a numbers-matching L79 and (to a lesser extent) L46 would prove to be expensive, so we did the next best thing. We assembled test motors using all of the important components that would best represent the power potential of each. Starting with the 327, we assembled a short block using 11.0:1 pistons (with 7.5-cc domes), factory 5.7-inch rods, and cast (large-journal) 3.25-inch stroke crank. Both the 327 and 350 were built using (early) 4-bolt blocks, each bored .030 over (required for clean up). The 350 also featured a cast crank (3.48-inch stroke), 5.70-inch rods, and forged pistons featuring 2.5-inch domes.

Both the 327 and 350 were combined with cylinder heads that featured 64cc combustion chambers. Each short block received Federal Mogul bearings, std-volume oil pumps, and hardened pump shafts from Speedmaster. After balancing (with Speedmaster dampers) by L&R Automotive, the short blocks were ready to receive their respective cylinder heads and induction systems.

The L79 327 received a set of big-valve, 186 iron (fuelie) heads, while the L46 featured 492 castings. Both sets of raw head castings were in excellent condition but were nonetheless treated to new stainless steel (2.02/1.60) valves from Speedmaster, along with 3-angle valve jobs. To ensure rpm potential, both sets were also given a set of COMP Cams valve springs that offered 130 pounds of seat pressure at 1.825 installed height. We took the liberty of measuring the chamber volume of each head casting, and they each checked in at 63cc. The flow rates of the two Fuelie heads were nearly identical, despite the difference in casting numbers.

The heads were topped with the high-rise, Holley combo on the L79 (though we substituted a 750 hp for the hard-to-find 600 cfm) and the low-rise and Q-Jet on the L46. Both engines received MSD distributors and long-tube headers and were treated to break-in cycles before running them in anger. Each was tuned by dialing in the air/fuel and timing values to maximize the power output. Neither engine was run with accessories; instead, we simply installed a Meziere electric water pump.

First on the dyno was the L79 327. After the break-in and oil change, we spent some time playing with ignition timing and carb jetting. Once dialed in, the short-stroke, L79 muscle mouse produced peak numbers of 345 hp at 5,400 rpm and 381 lb-ft of torque at 3,900 rpm. The hot street motor offered impressive grunt, with torque production exceeding 375 lb-ft from 3,400 rpm to 4,400 rpm. Torque production exceeded 350 lb-ft from 3,000 rpm (possibly lower) to 5,100 rpm. Though peak power production occurred rather low at 5,400 rpm, power production dropped only slightly out to 6,000 rpm.

Given the same treatment on the dyno, the 350-hp L46 350 produced peak numbers of 351 hp (at 5,500 rpm) and 393 lb-ft of torque (at 3,800 rpm).

Looking at the peak numbers, we see the larger 350 offered just 6 hp and 12 lb-ft, but a review of the curves (see dyno graphs) show the real difference. Down at 3,000 rpm, the larger 350 offered an extra 27 lb-ft of torque. Such is the benefit of displacement, but regardless which of these amazing small blocks you happen to own, chances are you aren’t in any hurry to trade for the other, not matter what the difference is.

Sources: COMP Cams, compcams.com; GMPP, gmperformanceparts.com; Holley/Hooker, holley.com; JE Pistons, jepistons.com; L&R Automotive, lnrengine.com; Speedmaster, Speedmaster79.com; Sean Murphy Inductions, smicarburetor.com