Of course, Bill “Grumpy” Jenkins didn’t invent the big-block 1967 Camaro but his touch in choosing, prepping, tuning, and driving his now famous, plain white ’67 Camaro made a lasting impact on the popularity of the make.
Grumpy Jenkins’ drag racing career began like many young men who grew up in the 1950s. In those days, Jenkins was known not as “Grumpy” (that came later, due to Jenkins gruff facade), but “Jiggs” Jenkins. A mechanical aptitude developed at an early age allowed him to quickly acquire an in-depth knowledge of engines. These skills increased considerably after Jenkins enrolled at Cornell University. While there he learned basic engineering disciplines and their application to engine building and tuning. Soon, other drag racers were eager to pay for the counsel and hands-on touch available from one Jiggs Jenkins.
During the 1960s, Junior Stockers acquired a near cult following, especially on the East Coast. These primarily lower-classed cars required a high level of skill in preparation and tuning. Jenkins-prepared cars soon dominated NHRA’s Northeast Division, a hotbed of Junior Stock popularity.
In 1961, Jiggs began working with Chevy’s W series 409. This “big-block” type engine was designed for trucks and fullsize cars. Beginning with a 1961 409 Biscayne sedan, Jenkins uncovered surprising horsepower from the cumbersome W engines. His association with friend and customer Dave Strickler produced numerous NHRA records and Stock Eliminator wins with the 409.
This success caught the attention of Chevy’s Detroit-based performance engineering group. Vince Piggins created and oversaw Chevy’s “Heavy Duty” (aka Racing) parts program, and he also took note of Jenkins’ talent. This friendship grew to become a close alliance that kept Jenkins in the loop, especially at GM’s sprawling “Tech Center” complex in Warren, Michigan, and Jenkins was forever rumored to have clandestine “help” from the Bow Tie boys. Chevy’s last gasp for the W series engines produced the Z-11, a 427ci, 430hp engine and aluminum front end package for the 1963 Impala. It was Bill Jenkins who skillfully prepared and tuned a ’63 Z-11 Impala that Dave Strickler drove to Little Eliminator at the 1963 Nationals.
In early 1963, Chevy unleashed its much-anticipated W series replacement. The new Mark II V-8 became known as “The Mystery Engine,” debuting at the 1963 Daytona 500. Henry “Smokey” Yunick’s Mark II-powered 1963 Impala took the pole and led early until valvetrain failure forced him out of the race. These problems were quickly remedied, but the fickle winds of Detroit politics forced the withdrawal of all Mark II engines before Jenkins had a crack at them for drag racing.
The Mark II remained a mystery for several years until the 1965 model year passed its halfway point, when Chevy abruptly halted production of the 409. Instead, an optional 396ci engine was offered in horsepower ratings from a mild 325 up to 425. The new 396 was called the Mark IV, but there was no mistaking its Mystery Engine heritage.
The 396 came in both “low hp” and “High Perf” versions. The lower-rated engines were equipped with smaller, oval-shaped inlet ports for better low-rpm velocity and were known as “Oval Port” heads. The performance heads had the words “Hi Perf” cast on their intake runners and came with much larger inlet ports. These heads were known as “Rectangular Port,” or “High Perf” heads.
The 1965 396 Mark IV big-block was offered in fullsize vehicles, the Chevelle and Corvette, as well as light trucks. Top power output came from the L78 option, a 396 with a Holley four-barrel carburetor; single-point Delco distributor; forged steel crankshaft and rods; four-bolt main bearing block; forged-aluminum, 11.0:1-compression pistons; and a mechanical lifter camshaft.
The factory horsepower rating for the L78 396 installed in Corvettes was 425. When the same engine went into a fullsize Chevy it was a 375hp 396. The 396/375 was also used in a brief run of 1965 Chevelles with the Z-16 option code.
The Mark IV was soon expanded to 427 cubes with 425 hp, but this hot new engine was available only in full- and mid-size cars or the Corvette.
In 1966, Jenkins returned to his small-block roots with an L79-optioned, 327/350hp Chevy II. Its light weight placed the Nova in NHRA’s A/Stock class, pitting it directly against the 426 Hemi. This seeming mismatch propelled Jenkins to legendary status with his giant killing, small-block Chevy II. Jenkins also blew away NHRA’s Hemi-dominated A/S record to 11.66! The little Chevy II was also adorned with the “Grumpy’s Toy” moniker for the first time.
Jenkins’ success with the Chevy II set the stage for the division’s first “pony car,” Chevy’s new 1967 Camaro.
The new ’67 Camaro came as a base vehicle with a disappointing six-cylinder engine, a small-block 283 or 327, plus a new engine: the 350 V-8.
Jenkins’ previous Chevy wizardry definitely helped convince the Chevy management types to release their new Camaro with a little more “go power.” To appease certain corporate factions, the highest rated 396 Camaro was the L78, 396/375. Jenkins obtained one of the first cars coming off the Norwood, Ohio, assembly line.
Jenkins’ imagination jumped into overdrive when it came to increasing the performance of his new big-block, ’67 Camaro. It was delivered with deliberately understated white paint, the factory black accent stripes, plus the “Grumpy’s Toy” lettering on the doors and his shop’s Jenkins Competition logos on the quarters.
Jenkins loved to row through the gears, so the car was fitted with a Hurst Competition-Plus shifter controlling a four-speed Muncie M21 transmission.
The L78 engine appeared unchanged from the assembly line, save for the Hooker headers with 2-inch primary tubes. They replaced the efficient yet heavy cast-iron manifolds.
NHRA’s Super Stock rules required the stock cast-iron, closed-chamber cylinder heads. These housed 2.20-inch intake valves and 1.88-inch exhaust valves controlled by dual valvesprings. Screw-in rocker studs and pushrod guideplates were used with stamped steel, pivot-ball 1.7:1 ratio rockers. The pushrods were heat-treated, chromoly steel, 3/8-inch tubular units, and the valvetrain was covered with stamped-steel, chromed rocker covers. Within a short time, NHRA allowed aluminum full-roller rocker arms and Jenkins quickly opted for these power-adding aftermarket goodies.
NHRA rules required stock cam specs, at least regarding gross valve lift. This allowed for a little hot rod ingenuity, and that meant stock lift with more duration and a tighter lobe separation. Interestingly, the same factory cam was used in the later L72 427/425. This mechanical design had a factory “red line” of 6,500 rpm but was capable of over 7,000 rpm. The stock duration was 242 degrees at 0.050-inch lobe lift; 0.520-inch lift, intake and exhaust; 114-degree lobe separation; and lash sets at 0.024-inch intake and 0.028-inch exhaust. The stock Chevy cam was good, but specialized race cams were better.
The stock intake manifold was required, but the factory cast-aluminum, high-rise, dual-plane intake was well-engineered and carried a Holley 780-cfm, four barrel carburetor, List Number R-4346.
One of the “tricks” of the Gen-1 big-block Camaro racers was substituting big-block motor mounts with a pair of small-block mounts. This moved the engine rearward between 1/2 and 3/4 of an inch, producing a slightly more favorable front/rear weight bias in the nose-heavy car.
The ’67 Camaro came with monoleaf springs that produced extreme wheelhop. Jenkins fabricated a bolt-on rear traction bar system with a hard-rubber snubber that contacted the leaf spring itself. These proved to be very versatile and Jenkins allowed Lakewood Industries to market them as “Traction-Action” bars. Most racers simply called them “Bump Bars,” and they remain popular today.
Jenkins’ new ’67 Camaro fell into NHRA’s Super Stock/C. His plain-white Grumpy’s Toy frequently won, and at the biggest race of the year, the 1967 NHRA Nationals, Jenkins swept Super Stock Eliminator; a career-defining win.
Jenkins’ 396 Camaro served him for many years after the 1967 season. Match racing became hugely popular in 1968-’69, and the ’67 was quickly converted to a heads-up match racer. This entailed relieving the car of all unnecessary weight, fitting a Grump Lump fiberglass hood and scoop and dropping in a maximum-output 440ci big-block with aluminum heads, a deep-plenum, tunnel-ram manifold, and a pair of Holley 660-cfm “center-squirter” carbs. For 1970, Grumpy used the ’67 for his first legal Pro Stocker. It carried Jenkins to hugely popular Pro Stock wins in its first two events of the 1970 season: Pomona and Gainesville, where he defeated Mopar’s ace, Ronnie Sox.
Jenkins parked the ’67 for a while, running his 1969 ZL1 Camaro, and later, a new second-gen Camaro. In 1971, the reliable old ’67 Camaro returned again, this time as an underground test mule. Fitted with a 331ci small-block, the Camaro made quiet test runs at a heavier weight break, proving to Jenkins that a small-block powered sub-compact Vega could compete with weight factored Pro Stocks. Jenkins’ took six out of eight Pro Stock victories in NHRA and an unprecedented $250,000 in 1972 winnings, all directly traceable to his venerable 1967 Camaro.
Chevy offered the L78 396/375 through its 1971 model year. Although still badged “396,” the 1970-’71 396 was overbored 0.030 becoming a 402-inch engine. The ’67 L78 big-block evolved further, and in 1969 Chevrolet created the most powerful Camaro engine combinations ever: the L72, 425/427 “COPO” option and the outrageous ZL1, an aluminum alloy 427 ridiculously under-rated at just 430 hp.
Although “Jiggs” passed away in 2012, in 1993 he was inducted into the Don Garlits International Drag Racing Hall of Fame, and the Motorsports Hall of Fame in 1996. These greatly deserved honors are at least partially attributable to his ’67 big-block Camaro.
Of the 5,181 big-block cars produced in 1967, only 1,178 were L78s. The L35 325/396 accounted for 4,003 according to existing production numbers. Those vehicles, and especially Bill “Grumpy” Jenkins’ plain-white Camaro set a lofty standard by which Chevy race cars continue to be measured.