Have your iconic lumpy cam lope and brake vacuum too

Words: Brandon Flannery

The horsepower wars of the 1960s and ’70s were an exciting time. As American life grew increasingly mobile, people’s car-centric love affair with speed blasted off like the space program. Technology of the mechanical age was buzzing towards its zenith, and unbridled exploration was hip. In auto racing, faster cars that won on Sunday meant sales on Monday; automakers responded with enthusiasm.

Under the hood, compression ratios escalated and carburetors multiplied as manufacturers offered cars at their top tiers that were barely streetable. Thinly-disguised racers that required special warning stickers and careful valve adjustments were effortlessly sold to the power-hungry public. At the heart of these legendary, sometimes mythical, engines was a camshaft designed to wring out every last ounce of power. These cams quickly became the hot ticket for guys building potent street cars across the land, and some remain popular several decades later.

With time comes refinement and technological progress. Today’s highest peak will eventually become a stepping stone for tomorrow, and engine power is not immune. Solid lifter valve trains gave way to hydraulic systems that were quieter and maintenance-free. Flat tappet cam followers gave way to rollers that allowed tighter incline changes, which then changed the shape of the cam lobes. Spring technology and an understanding of harmonics alleviated massive spring pressures and increased rpm limits. Today’s computer-designed cam profiles can be asymmetrical and even multiple patterned. They make more power, more vacuum, and idle better while increasing off-throttle or low-end response.

Great strides have been made in refining horsepower, but for some, a little essence was lost in the transition. Most importantly, the iconic sound. No self-respecting gearhead overlooks the distinctive lope of a classic high performance engine. The clackety song of mechanical lifters hitting valve stems, the choppy idle, and the hands-on ceremony of adjusting the valves were part of what made these engines great. To have a really authentic restoration or a period-correct build, these elements need to be in place.
For the guys who care about mechanical authenticity, COMP Cams developed their Factory Muscle line. They whittle new cam cores to old specs using modern grinding and surface finishing techniques. Other than an NOS part, these are as close to original as you can get for the superstar cams of the ’60s and early ’70s. They may be even a little better with today’s surface finishing.

But what about those who would like to have their cake and eat it too? Say, a lope and vacuum? The engineers at COMP asked that very question and answered it with their Nostalgia Plus series. It provides all the things you love about the originals without the things you hated. Vacuum and drivability were greatly improved while staying very close to the original specs. Keep the choppy idle, mechanical solid lifters, and high rpm and gain a little vacuum, power, and torque, yet to even the keenest of ears, it sounds the same.

By far, the camshaft that kicked off the frenzy was the famed Duntov 30/30, named for its designer, Zora Duntov, and .030 “hot lash” setting. It featured 0.480-inch lift with 300 degrees of duration. The long gentle ramps allowed high revs without valve float, even with a stock 85-pound spring on the seat.

“Our Nostalgia Plus series is our modern interpretation of these designs,” says Dean Harvey of COMP. “With these, we looked to the original designs and gave them the ‘tweaks’ that made our High Energy, Magnum, and Extreme Energy designs popular. Just like anything, modern technology has opened up new thoughts with the design of camshaft lobes. And of course, COMP engineers, never ones to stand still, pushed the envelope on these designs and came up with profiles that made more torque and horsepower over their factory-designed cousins. I think it is a fitting tribute to the early cam designers; they laid the path for the current crop of cam designers and have allowed them to make great designs of the period even better today.”

Their lineup of Nostalgia Plus camshafts cover all the greats, from Ford and Chevy to Chrysler. They include versions of the Duntov 30/30, the 300-hp L-79, and the LS6 from Chevrolet, most of the “Purple” camshafts from Direct Connection/Mopar Performance, and Ford’s famed 271 cam. If you know what these are, then you are finished reading. If the above list of letters and numbers has your mind scrolling through the memory files and you’d like some reminder help, please read on.

Let’s start with Chevy. At the green flag of the horsepower race was the OHV V8 from GM. In 1955, the “shot heard ‘round the world” was the new V8 in the Chevrolet. No other engine family would go so far, or achieve so much. As their popularity grew, so did their horsepower ratings.

Duntov 30/30

Starting from the beginning, the Duntov 30/30 is one of the most famous cams ever. It’s name is derived from its designer, Zora Argus Duntov, and the recommended “hot lash” setting for the valves. With very long clearance ramps, setting them at TDC was finicky. Savvy racers have since learned that with a little care, 90-degrees ATDC for the intake and 90-degrees BTDC for the exhaust puts the lifters well on the base circle for a more accurate setting. However, the popular Duntov 30/30 was used in the 365-hp L-76 ver-sion of the Corvette’s 327 in 1964-65, the 375-hp L-84 327 in Fuel Injected Corvettes, and again in the DZ302 Camaro Z/28s in 1967-69.

L-79

The notorious L-79 versions of the 327-powered Corvettes of 1965-68 made 300 hp with 11:1 compression, forged pistons, and an aluminum intake with a Holley carb. They also featured the first high performance hydraulic camshaft ever offered. With a 2,400 to 5,800 rpm powerband, they ran 15-second quarter mile times right off the showroom floor. These cams had great throttle response with a great power curve and made decent vacuum with a nice lumpy 800 rpm idle all the kids went crazy for. In fact, from 1965 to 1980, there were more owner-installed L-79 camshafts in ‘57-’74 Chevy small blocks than any other grind.

Mopar cornered the lion’s share of the aftermarket sales with their factory-authorized Direct Connection special parts company. Their “Purple Cams” were a huge hit and came in varying degrees of power levels.

LS6

The race for power resulted in a lift on big engines in mid-size cars, and Chevy’s answer culminated in the LS6 454c.i. big block in 1970 and ’71, factory rated at 450 and 425 hp, respectively. Showroom Stock Automatic class cars were hot at the drag strips, and the LS6-equipped cars did very well. The 11.25:1 compression ratios breathed through a solid mechanical lifter valvetrain with a .316/.301 and .520 lift cam. Rumors of the factory “lowering” the factory horsepower ratings (or even outright lying) were put to the test with the “Benchmark LS6,” a 19,000-mile survivor. With the engine out for detailing, the rumors were finally put to the test on a dyno in stock trim. Tests resulted in an honest 452 hp at the flywheel. However, with a simple one-inch carb spacer and a set of headers, power jumped up to 512 at the 6,500 redline. The factory manifolds were found to be fairly restrictive.

Mopar Purple Cams

Chrysler’s impact on drag racing is legendary. The “after hours” activities of their engineers took “factory development” to the next level and changed the face of the sport. Chrysler’s Marine and Industrial Engine Division also made racing engines and in 1962 released a small mail-order catalog called “Chrysler Maximum Performance Packages.”

In 1964, many of the engineers who were active in racing on Detroit’s famed Woodward Ave were also staffing Chrysler’s Special Parts Service, allowing customers to purchase their latest innovations. In the early 1970s, those engineers established the Direct Connection Brand that offered factory-developed and factory-approved performance gear and customization products for Mopars. This eventually morphed into Mopar Performance Parts. Direct Connection was very active in racing in the 1970s, and their cam-shafts came with a purple coating between the lobes, thus earning their name. They offered several levels of performance for both big and small blocks.

Ford 271

When Ford introduced the Mustang in the middle of 1964, high-winding small blocks were king. Though the majority of the Mustangs came with inline sixes, some were treated to a V8. The 289 lent itself well to the platform, and quickly found success on and off the track.

A special “HiPo” version that made 271 hp at 6,000 rpm was first offered in 1963. It was introduced in the Fairlane, then the Comet, and finished its run in the Mustang in 1968. It also powered the first Shelby AC cobras and the Shelby GT350 Mustangs through 1967.

The HiPo 289 was given the letter K, and is known as a “K-code” engine. They feature stronger connecting rods, a high nodularity cast iron crankshaft, different harmonic balancer, screw-in rocker studs, a 600cfm Autolite carb, dual-point mechanical advance distributor, and a solid lifter cam with a slow ramp, low lift, and a lot of duration that allowed a higher rpm peak. Ford only offered a four month warranty on the High Performance engine, versus the two-year warranty on all other cars. Obviously, they knew they were going to be heavily raced.

Source: COMP Cams, compcams.com