Dyno Testing chevy's Famous Hydraulic Cammed Small Blocks - Legendary Small-Block Shootout-The Sequel

This Month We Test Hydraulic Horsepower: It's L79 Vs. L46 Vs. L82.

Richard Holdener Mar 1, 2010 0 Comment(s)
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By comparison, the L82 was essentially a low-compression L46, as emission regulations eventually resulted in an across-the-board drop in static compression ratio (from 11.0:1 to 9.0:1). The net power rating of the L82 ranged from a high of 250 hp to a low of 205 hp ('75) during the eight years of production ('73-80). Just how would the 250hp (net) L82 compare to the 350 hp (gross) rating of the L79 and L46? That's what we were here to find out.

L79 350-HP 327
First up was the 350hp L79 327. The build up of this motor was a simple matter of replacing the solid Duntov 30-30 cam in our L76 327 with the GM Performance Parts L79 grind (PN 3863151), or so we thought. A call to GM revealed that only the L46 cam was still available and we had to shop elsewhere for the L79 stick.

Leafing through the Comp Cams catalog revealed that it indeed offered a reproduction of the factory L79 cam under the Factory Muscle heading (PN 12-1060-3). Retained were the 461 intake, the 186 fuelie heads and 11.0:1 compression ratio. As with our previous trio, we ran all three of these hydraulic cammed small-blocks with a set of 1 3/4-inch long-tube headers. We used a Holley 750 HP-series carburetor (larger than the factory Holley originally run on the L79) so this definitely gave it an advantage. (The L46 and L82 were run with a Rochester Quadrajet supplied by Sean Murphy Inductions.)

Sucp_1003_03 Chevy_small_block_hydraulic_testing L79 2/23

It is likely that the 750 Holley helped the L79 more than the previous solid-cammed combinations as the L79 was equipped with a smaller carburetor than the 780s (4150) used on the LT-1 and 302. Because of the number of letters received on the subject, we also took the liberty of replacing the 6.0-inch connecting rods and attending pistons with the factory-length 5.7-inch rods.

The dome design was identical, the only change was the compression height on the piston. Before making the swap to L79 specs, we ran the L76 with the new piston/rod combination to register the difference between the different rod lengths. The graphs were identical with less than 1-2 hp difference anywhere in the curve. Basically we did a lot of work for nothing, but nothing is too good for the readers of Super Chevy.

Sucp_1003_06 Chevy_small_block_hydraulic_testing Forged_aluminum_pistons 3/23

With our back up work performed, it was time to run the L79. We installed the Comp L79 grind and matching hydraulic flat-tappet lifters along with a can of high-zinc break-in lubricant from Lucas Oil. Naturally the cam and lifters were liberally coated with a moly-based assembly lube prior to installation and we allowed the new cam plenty of break-in time (keeping engine speed above 2,000 rpm) prior to making our power pulls. After dialing in the ignition timing and carb jetting, the L79 produced peak numbers of 345 hp at 5,400 rpm and 381 lb-ft of torque at 3,900 rpm. Torque production exceeded 375 lb-ft from 3,400 rpm to 4,400 rpm and exceeded 350 lb-ft from 3,000 rpm (and lower) to 5,100 rpm.

Sucp_1003_04 Chevy_small_block_hydraulic_testing L79_hydraulic_flat_tappet_cam 4/23

The 327 produced peak power at just 5,400 rpm with the hydraulic flat-tappet cam, but remained relatively flat out to 6,000 rpm, dropping by only 12 hp. We were not surprised by the torque production of the hydraulic-cammed 327 (compared to the previous solid-cammed L76), but we were surprised to see the peak power numbers produced by the L79. Despite a drop in cam timing of over 30 degrees (at 0.050) compared to the Duntov 30-30, the L79 still managed to produce just 10 hp less than the L76. No doubt, the larger carb helped, but it is no wonder the L79s had such a strong reputation on the streets back in the mid-late '60s.

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