Replicating The L79 327 – Was It Chevy’s Best Small-Block?
By Chuck Hanson
October 7, 2024
There once was a time, believe it or not, when even the idea of the LS engine platform hadn’t yet been conceived, and a seemingly endless supply of first-gen small-block Chevys fed the performance dreams of millions of performance enthusiasts. But while the supply of early small blocks may have diminished in recent years, the legend lives on.
First introduced in 1955, the 265-cu.in. version was the main source of motivation for the newly redesigned Chevy passenger cars and light trucks. The new engine’s compact, lightweight design and potential to produce impressive power made it an instant hit with the performance crowd and it quickly usurped the venerable Ford flathead as the preferred power source for nearly everything on wheels.
Inspired by its popularity, the engineers at GM pushed further in developing the small-block’s potential, while simultaneously, the performance aftermarket developed hardware to facilitate in exploiting engine’s inherent strengths, feeding the public’s insatiable appetite for more power. Success came quickly and in abundance, as trackside conquests translated immediately to the street, and the market for the small block in all variations grew exponentially.
Not surprisingly, the small block quickly became somewhat ubiquitous in performance circles as it grew rapidly from 265 cubic inches to 283, then 327, 350, and eventually 400 inches of displacement in factory form. In aftermarket trim we’ve seen them stretched all the way to 454 cubic inches, with several companies offering aftermarket blocks and heads to ensure further evolution. And now there’s even a rumor of a 600-cu.in. version currently in development. For the sake of this discussion, however, we’ll limit ourselves only to factory offerings.
If one listens long enough, the dispute over which first-gen small-block is/was “the best” has been in contention nearly as long as the platform has existed. And it’s doubtful that debate will ever be resolved… at least in the minds of some enthusiasts. But we’ll put this out there: The 350-horsepower 327 (RPO L79), available from 1965 through 1968, can offer a solid case for the argument, with good reason.
How The “Mouse” Motor Earned It’s Name
The story of how the small-block Chevy acquired the nickname “mouse” is said to have been in response to the Chrysler Hemi being referred to as an “elephant.” Legend has it that elephants are afraid of mice, so the Bowtie loyalists began calling the potent small block the mouse for reasons that were soon reverberating through the entire racing community.
Perhaps the biggest contribution to the L79 legacy was the engine’s considerable success on dragstrips across the country, most notably with Bill “Grumpy” Jenkins, who almost single-handedly rewrote the record books in nearly every class he and his Chevy II ran. In fact, his record of success, even against the seemingly invincible Hemis, earned the diminutive small-block a reputation as “the elephant killer.” Indeed, competitors needed to bring their “A” game whenever they lined up against “Da Grump!”
Okay, we can hear the voices of discontent already, and we’ll certainly concede that there were factory-produced small-blocks with more displacement and more power. Of those, the higher-horse versions were generally fitted with flat-tappet, solid-lifter valvetrains that were finicky and required frequent adjustments to maintain their tune. This became especially acute if the person controlling the throttle was inclined to pursue the suggested horsepower numbers in the elevated rpm ranges. We also concede that, indeed, the small block sings a sweet song above 6,000 rpm, so we fully understand the temptation.
Fuel injection was another source of additional horsepower, but the attention required to keep it functioning properly brought another level of expertise into the formula; one that not many backyard mechanics possessed.
Components endemic to the L79 included a high-performance hydraulic cam, 11:1 forged pistons, a steel crank, free-flowing heads with 2.02/1.60-inch intake/exhaust valves and tight 64-cc combustion chambers, and an aluminum dual-plane intake manifold mounting a Holley 585-cfm four-barrel carburetor. It was a high-performance package that offered incredible performance without the maintenance regimen of its solid-lifter brethren, making it an attractive option for performance enthusiasts that wanted the acceleration without the aggravation.
Camshaft, compression, and engine speed all contribute significantly towards making great power, and Chevy’s engineers found ways to utilize all three to their advantage, even to the point of exceeding the power output of the base big blocks. This, of course, created a bit of a marketing quandary, and forced a reshuffling of the power ratings in order to keep the big-block’s reputation intact.
What Vehicles Came With The L79 327 Cu.-In. V-8?
The L79 retained its 350-horse rating for ’65 as it was planted between the fenders of the Corvette and Chevelle; the rare Z16 Chevelle was offered only in limited quantities and its 396 carried a rating of 375 hp, so the big-block’s reputation was secure for the time being. But with the introduction of the ’66 SS 396 Chevelle and its massive marketing push, the 350-horse 327 found itself conspicuously absent from the A-body’s powertrain lineup. Apparently, Chevy market planners were concerned it would overshadow the base 396 and its 325-horse rating. It was still an available option in the Corvette and the Nova however, with its 350-horse status.
With its strong following, customer demand for the powerful small block forced its reintroduction in the ’67 Chevelle, and while it was still essentially the same engine, the power rating was refactored from 350 to 325 horsepower. That rating was for the Chevelle only; the Corvette and Nova retained the 350-horse ranking. Then, in ’68 the L79 underwent a substantial change to the intake tract. The previously employed aluminum intake and 585-cfm Holley four-barrel carb were replaced with a cast-iron intake mounting a 750-cfm Quadrajet. The rest of the L79 componentry, however, remained the same as previous years. Again, the power ranking held at 325 for the Chevelle and was shared with the Nova (which was fitted with the big-block for the first time in the new-for-’68 body), while the Corvette was awarded the 350-hp status again in deference to an allegedly freer-flowing exhaust. It’s interesting to note that the L79 never made an appearance in any full-sized Chevy.
Designing A Proper L79 Replica Build
With such a tremendous amount of success, one must wonder, “What kind of horsepower did the L79 really make?” It’s a fair question; one that we hope our “tribute” engine will answer by the end of this story. Of course, our engine will be built as close to factory spec as possible, without all the special prep and tricks usually employed in race engines to extract every conceivable bit of power.
This engine came into our possession from an aspiring drag racer whose intent it was to emulate Jenkins’ straight-line accomplishments. He’d gathered much of the requisite hardware, but before completing the project he ran out of time, money, and ambition.
The block was a well-used ’67, small-journal 327, with two-bolt mains and a need for a .030-over punch to make the cylinders compatible with the vintage TRW 11:1 pistons included in the sale. The steel crank was also present and checked standard/standard on the mains and rods. Poor storage made us cringe when we first saw the heads. Although they featured the correct “462” castings and 2.02/1.60-inch valves, they were rusty, crusty, and questionable as to whether they could be saved. We quickly carted the entire mess to Tommy’s Auto Machine in Springfield, Tennessee for evaluation and necessary machine work.
Once the process began, we were pleasantly surprised to learn that despite outward appearances, all the bits and pieces were deemed usable. Towards that end, the block was cleaned, align bored, squared, and decked to ensure dimensional integrity. The crank was straight and cleaned up amazingly well with only a quick trip to the crank polisher.
The pistons included in the sale are TRW originals from the early ’70s. Although they are configured the same as current offerings and even share the same L2166 part number, the applied coating is vastly different and was probably “high tech” for back in the day. The rods that were also included in the package were original steel pieces, utilizing 11/32-inch bolts, which we’ve always felt were questionable for a high-performance application. To gain some reassurance, we replaced them with a set of Scat I-beam rods featuring 3/8-inch ARP cap screws.
Finding an NOS replacement for the long-discontinued L79 camshaft would have qualified as a near impossibility, and very likely expensive even if we were to get lucky. But Comp Cams has a remake of the original, featuring the same exact duration and lift specs; their kit arrived with compatible springs, retainers, and locks. Comp has also addressed flat-tappet cam failures with the introduction of its High Energy DLC (Diamond-like Carbon) lifters that have a special coating on the lifter face to reduce friction and significantly reduce the possibility of cam lobe failure. Choosing the new technology was a no-brainer.
After determining which bearings, rings, and gaskets we needed, we placed an on-line order with Summit Racing, where everything was in stock (we even qualified for the free shipping!). Even better, the order was delivered to our doorstep in only two days, and we were able to get the project quickly underway. Assembling our remake of the L79 was straightforward; click through our slideshow below to look at how it all went together.
Leading In The Right Direction
The L79 came from the factory with many enhancements to help it produce its legendary performance, most notably the heads with generous intake ports and large (2.02/1.60-inch) valves. To add a bit more valvetrain stability, we had the heads machined for ARP screw-in studs and Comp Cams guide plates.
After removing the original rocker studs, the bosses were machined flat to accommodate the guide plates, and then tapped for the screw-in studs.
The valve seats and valves were the recipients of a three-angle valve job to enhance flow and promote superior sealing.
After installing new bronze valve-guide liners, Summit stainless valves were slid into position to fill the combustion chambers.
Comp Cams valve springs, retainers, and locks were used to ensure valvetrain compatibility. A pneumatic valve-spring compressor made the task quick and easy.
Dyno Testing Results
Even though our ’67 vintage L79 carried a 325-hp rating, it still retained the same components as earlier versions with the 350-horse tag, so we expected our dyno test to reveal a number in that range. It didn’t disappoint us. Even more impressive, however, is the relatively flat torque curve that peaked at 368 foot-pounds and didn’t fall below 325 until about 5,800 rpm. Now that’s real grunt in a usable range, enabling the small-block to work quite effectively and yield solid performance.
Lubrication for any engine being fired up for the first time is critical, so before the dyno session we filled the crankcase with Driven non-synthetic break-in oil; it has special high zinc additives to minimize wear and friction during the initial stages of break in. Check out the numbers:
SOURCES
ARP (Automotive Racing Products) • 800-826-3045 • arp-bolts.com
Comp Cams • 800-999-0853 • compcams.com
Driven Racing Oil • 866-611-1820 • drivenracingoil.com
Federal Mogul • drivparts.com/federalmogul
Fel –Pro Gaskets • 800-325.8886 • felpro.com
Holley Performance Products • 866-464-6553 • holley.com
Melling Engine Parts • 517-787-8172 • melling.com
MSD Ignition • 866-464-6553 • holley.com/brands/msd/
Sealed Power • drivparts.com/brands/sealed-power
Scat Racing Components • 310-370-5501 • scatcrankshafts.com
