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1969 Chevrolet Corvette LT-2 Review

Motor Trend logo Motor Trend 2/9/2015 Frank Markus, Andrew Trahan

The year 1970 marked the end of an era in which Zora Arkus-Duntov enjoyed sweeping authority to develop and offer myriad performance engines in the Corvette. Chevrolet was bleeding some red ink. John Z. DeLorean was sent in to fix things, and one of his fixes was to "de-proliferate" the engine catalog, pruning a bunch of ultra-low-volume big-block motors that were covertly intended to supply independent racing teams. The car you see lovingly recreated here tells a pretty interesting story of what might have been had DeLorean's timing lagged a just a bit.

Then, as now, automakers tried to spice up their new model-year press preview events with some sizzle, and for the '69 and '70 model year show-and-tells Chevy rolled out a provocative Monaco Orange Corvette coupe stuffed full of the hottest engine in the pipeline. For 1969, that meant the mighty ZL-1 427. Optimized for racing applications -- despite GM's corporate edict against direct motorsport involvement -- it featured all-aluminum construction (the block was painted orange so folks thought it was an L-88), a hot cam, solid lifters, and high compression (12.5:1) to produce somewhere north of 550 hp and 530 lb-ft. Mated to a Turbo Hydra-Matic 400 automatic spinning through a 4.88:1 axle, it was ideally suited to Woodward Avenue street racing, so internally it was dubbed "the Saturday Night Special" (SNS).

1969 Chevrolet Corvette LT 2© Provided by MotorTrend 1969 Chevrolet Corvette LT 2 When this same high-caliber dragstrip weapon turned up the following summer, many assumed it packed the same hot hardware, and it kind of did—except the engine was updated to LT-2 specifications. The LT-2 was envisioned as the ZL-1's 1970 replacement atop a line of big-blocks, all stroked to 454 cubic inches: a 12.25:1 LS-7 aluminum-head/iron block L-88 replacement, an LJ-2 all-iron 11.25:1 replacement for the L-71 tri-carb 427, and a cooking-grade 10.25:1 LS-5. Sad to say, because of the deproliferation efforts, reduced emphasis on ultra-high performance, and increasing pressure from the insurance industry, the LS-5 ended up as the Corvette's only production big-block for 1970, though the LS-7 made it into the brochures and even into an Eric Dahlquist Motor Trend driving impression.

The LT-2 in the SNS featured a Tufftrided 4.00-inch-stroke crankshaft (this proprietary salt-bath process hardened the crank with nitrogen), an aluminum water pump, revised intake and exhaust ports, 12.5:1 compression, and dramatically different intake and exhaust systems. The former involved a NASCAR-developed Holley Dominator 4500 double-pump four-barrel carb flowing up to 1200 cubic feet per minute. (The engine would have to spin 9000 rpm to fully utilize that flow rate.) According to the development engineer on the program, Tom Langdon, "It didn't make any more than 2 or 3 more horsepower, but it was different, and they wanted it on there because it was different." That was doubly true of the wild-looking "180-degree" exhaust headers, which only added maybe 12 hp (and reduced fuel consumption slightly), but gave the car a distinctive ripping sound, devoid of the familiar fourth-order V-8 rumble.

1969 Chevrolet Corvette LT 2© Provided by MotorTrend 1969 Chevrolet Corvette LT 2 1969 Chevrolet Corvette LT 2© Provided by MotorTrend 1969 Chevrolet Corvette LT 2 In order to safely thrill journalists of all driving skill levels, the gear shift selector had a plate bolted on to limit travel, preventing manual shifting (and possible over-revving), and a little 11-inch torque converter from a Chevy II was installed for its high (4000 rpm) stall speed. All they had to do was stand on both pedals, release the brake, and enjoy the sensation of a trebuchet launch. This drivetrain was stout. During the course of that press week, 71 acceleration runs were made, with an average ET of 12.14 seconds and a best of 10.89 at 130 mph. That's modern Nissan GT-R/Porsche 911 Turbo S performance in a lightened and modestly modified 1960s production car!

The car managed a 10.60-second 132-mph pass by dropping the gear lever from neutral to drive at 7000 rpm!

Some bonehead ran over the timing-light equipment before Motor Trend 's Dahlquist had a go, but the team invited him to come back a week later, at which time he learned a bit more about this special car. Drag-racing optimization measures included replacing the bumpers with chromed fiberglass, installing a thinner windshield and Plexiglas side windows sans motors, and removing the windshield wiper and hidden headlamp mechanisms along with the heater for a total weight near 2800 pounds (versus 3285 for a base, stock 'Vette). Chassis release engineer Dan Crawford explains that the F41 sport suspension was altered with "9010 uplift" shocks in front and big rubber snubbers limiting rear jounce and wheelhop. At Dahlquist's session, the car managed a 10.60-second 132-mph pass by dropping the gear lever from neutral to drive at 7000 rpm (!). That would have had it running neck and neck at the lights with an AWD, V-12-powered 2014 Lamborghini Aventador, had time travel been invented. Official dyno sheets show an output of 588 hp at 6400 rpm and 542 lb-ft at 4800 rpm.

1969 Chevrolet Corvette LT 2© Provided by MotorTrend 1969 Chevrolet Corvette LT 2 Just as generally happens with engineering test mules, that orange beast was dismantled shortly thereafter, never to be seen again, the fate of its engine a mystery. Enter Dave Miller, a devotee and restorer of vintage gasser drag-racing cars who had come into possession of a ZL-1 engine. He expected to install in some vintage gasser, but he wasn't aware of any renowned ZL-1 drag racers to replicate. Then he heard the legend of the Saturday Night Special long-lead press event car. He didn't believe it until his friend Kevin Lambert introduced him to powertrain engineers Gib Hufstader, Tom Langdon, Dan Crawford, and other retired engineers who confirmed the details. He dug for documentation -- at the GM Heritage Center and in Motor Trend 's photo archive, where Thomas Voehringer unearthed a folder cryptically labeled simply "1969 Long Lead."

With a trove of photographic and documentary evidence in hand, the Long Lead Corvette (LLC) project got rolling, with GM retiree Werner Meier's MasterWorks shop in suburban Detroit leading construction. The team found a '68 coupe donor car that had begun its life assigned to the public relations staff at Chevrolet, having been delivered a week before the date on the first GM work-order sheet, a line item of which was to update its trim to 1969 specifications. The block markings suggest the engine might have been the third one cast, and its date stamp suggests it was built near the same time, so both are period correct and either could conceivably (but unverifiably) have been used in the original SNS. Its frame was a rusty mess, so a second donor vehicle provided support for the PR car's body.

Thanks to the abundant photographic evidence unearthed largely from the Motor Trend archive, every sticker, decal, shock-absorber, and oil-filter label is as it appeared in the summer of '69 -- right down to the cobbled and riveted metal blanking plates over the disused rear exhaust outlets. The only details that are utterly incorrect are the panel fit and paint finish, which far exceed the scruffy mule's. And while the side windows are Plexiglas, their regulators and motors are installed, the headlamps work, and the bumpers are steel, which helps explain why this Long Lead Corvette re-creation weighs 175 pounds more than the SNS did. That's OK, because the stroked ZL-1 fitted to it reportedly dynos at 625 hp and 545 lb-ft, so the weight-to-dyno power ratio for each is 4.8 lb/hp.

Immense engine torque was causing the wheels to spin inside the tires, so inner tubes were fitted and the rim was screwed to the tire bead. Then, when the tires kept losing pressure, it was determined that centrifugal force was compressing the valve stem core and allowing air to escape if the valve stem cap wasn’t tightly fitted. The original wheels were magnesium; these are aluminum.© Provided by MotorTrend Immense engine torque was causing the wheels to spin inside the tires, so inner tubes were fitted and the rim was screwed to the tire bead. Then, when the tires kept losing pressure, it was determined that centrifugal force was compressing the valve stem core and allowing air to escape if the valve stem cap wasn’t tightly fitted. The original wheels were magnesium; these are aluminum. Fast-forward to a glorious, sunny, 62-degree Michigan May afternoon. Our orange Long Lead Corvette rolls off the trailer at Milan Dragway, and we're ready to find out at long last whether this recreated supercar is still capable of laying down modern-era supercar times. On hand to witness the event are retirees Gib, Tom, Dan, engine builders Denny Hummel and Vince Impastato, Meier, and many more. I take the wheel first, to drive the car over to the electronic scales (2975 pounds, with a 51/49-percent front/rear bias). It fires on the first half-revolution and settles into a frenetic and loud idle that sounds less lumpy than I expected. The sound jackhammering out of those side trumpets is like that of a flat-plane-crank Ferrari V-8 with much deeper lungs. (The firing cadence is identical, but a 7.4-liter flat-crank V-8 would shake itself to smithereens.) I press gingerly on the loud pedal, and nothing much happens for the first bit of travel -- then plenty happens. I lift with ample time to brake for the return road, given the minimal vacuum assist afforded by the high-overlap cam. The manual steering also feels surprisingly light and lively even at low speeds.

1969 Chevrolet Corvette LT 2© Provided by MotorTrend 1969 Chevrolet Corvette LT 2 Tom Langdon, drag racer and engine development engineer at GM from 1963 to 1999; right: Gib Hufstader, road racer and drivetrain engineer at GM 1950-1996 (back at GM Racing ’99-’04); at the wheel, Dan Crawford, pilot and chassis release engineer at GM 1957-2001.© Provided by MotorTrend Tom Langdon, drag racer and engine development engineer at GM from 1963 to 1999; right: Gib Hufstader, road racer and drivetrain engineer at GM 1950-1996 (back at GM Racing ’99-’04); at the wheel, Dan Crawford, pilot and chassis release engineer at GM 1957-2001. I'm informed that my gentle mile at the helm is the farthest the car has been driven to date. Nevertheless, next to shinny under the low steering wheel is local drag-racer Nick Serra. He makes two 80-percent-throttle shakedown runs and reports smelling oil. He thinks the timing might be too advanced, causing a mid-range misfire. Plugs are examined and replaced (idling on and off trailers will foul plugs in high-strung engines), their gap reduced from 0.045 to 0.030 inch per Langdon's recommendation. The timing proved to be accurate.

All they had to do was stand on both pedals, release the brake, and enjoy the sensation of a trebuchet launch.

Nick makes his first run in anger: 12.23 seconds at 112.28 mph (roughly the average of the 71 journalists' runs 45 years earlier) and compliments the brakes for stopping great with the throttle closed, but not holding too well for a brake-torque launch. There's still a misfire—maybe the original transistorized ignition just can't keep up? A second run at 10.86 at 124.64 mph, nearly replicates the SNS' best run at the press launch. A potential air-cleaner restriction is removed and the valve lash is checked, but that time will stand as the day's best, and everyone agrees that improving it will probably require installation of a high-energy ignition box. Then again, those are still modern-day supercar numbers.

Yes, the Milan launch surface is stickier than was the Milford Proving Ground asphalt, but then our LLC was running a taller axle than the SNS (4.56:1 versus 4.88:1), and we're only running 112-octane race fuel versus the 123 av-gas they ran back in the day, so let's call the playing field even. And let's tip our hats to the engineers, archivists, and craftsmen who, in recreating a Saturday Night Special, wrought a Tuesday afternoon miracle.

1969 Chevrolet Corvette LT 2© Provided by MotorTrend 1969 Chevrolet Corvette LT 2

1969* Chevrolet Corvette LT-2 "Long Lead Corvette" Specifications

Engine: 454.0-cu-in/7439cc OHV V-8, 1x4-bbl Holley Dominator 4500 carburetor
Power and torque (SAE net, per 2014 engine dyno test): 625 hp @ 6500 rpm, 545 lb-ft @ 5300 rpm
Drivetrain: 3-speed automatic, RWD
Brakes front: vented disc, rear: vented disc
Suspension front: control arms, coil springs, anti-roll bar; rear: multi-link, transverse leaf spring
Dimensions L: 182.5 in, W: 69.0 in, H: 47.8 in
Weight: 2975 lb
Performance then: quarter mile: 10.60 sec @ 132 mph ( Motor Trend, October 1969) Now: 0-60 mph: 2.8 sec, quarter mile: 10.86 sec @ 124.64 mph, 60-0 mph: 151 ft (Milan Dragway official timeslip)
Price when new: 1969 press-car development and modern-day recreation budgets undisclosed

*Then and now, a 1968 Corvette was modified to look like a '69, and fitted with a prototype '70 engine.


1969 Chevrolet Corvette LT 2© Provided by MotorTrend 1969 Chevrolet Corvette LT 2

ASK THE MAN WHO OWNS ONE

DAVE MILLER: is an economist and educator by training, and a lifelong car guy who once interviewed for a job with Petersen Publishing Company. His automotive passion and hobby is restoring and building vintage gassers. Having owned a Budget rental franchise and a used musclecar business, his automotive passion settled on historic gasser drag racers.

WHY I LIKE IT: "I love that the SNS was not a pricey original ZL-1, but rather a low-budget project, using off-the-shelf Chevrolet performance parts. Many of the engineers working on it were drag racers and street racers, so they saw this as their baby. They related to this one, and it's rumored it have been "tested" on Woodward Avenue a time or two; hence, the nickname they gave it."

WHY IT'S COLLECTIBLE: The car has no real value, except to illuminate a historical moment right at the end of the 1960s horsepower and performance wars. By the summer after it came out, performance cars were all but dead.

RESTORING/MAINTAINING: When recreating a car like this, the research phase is critical, and this car couldn't have been duplicated to this degree of accuracy without resources such as the GM Heritage Center and the Petersen Archives and the memories and documentation provided by the dedicated team of retired Corvette engineers.

BEWARE: When drag racing a Corvette, be concerned about the rear axle durability. If overwhelming torque meets stupendous modern-day tire grip, the result is likely to be universal-joint shrapnel in the axle shafts.

EXPECT TO PAY: (1970 454 LS-5/1969 ZL-1) Concours-ready, $70,400/$1.85M; solid driver, $54,200/$1.50M; tired runner, $20,000/$955,000. (Source: Hagerty Price Guide)

JOIN THE CLUB:National Council of Corvette Clubs, Corvette Club of America, National Corvette Restorers Society

OUR TAKE

THEN: "Against a national class record of 10.75 @ 128.75, [this result] is impressive. The fact that almost anybody who knows how to drive could jump in and duplicate this run after run may be the most shattering aspect of all."— Eric Dahlquist, Motor Trend, October 1969

NOW: Against a brand-new Lambo Aventador, this result from a vintage front-engine/rear-drive Corvette freshly reborn with absolutely no shakedown seems borderline supernatural.


Back in the day, engine expert Tom Langdon wasn’t a proponent of the hi-po 454s. The larger displacement exacerbated issues the L88 and other high-output 427s were having with connecting-rod bolds, piston pin retention clips, and crankshaft durability. He worked on both the production (budget constrained) Chevy big-blocks and the (cost no object) GM R&D big-block Chaparral program and reports that output levels of the best variants were not too different. Long (36-38-inch) tubes connect two cylinders from each bank into each collector, creating all the plumbing crossing under the oil pan and requiring the front suspension to be hiked up slightly. These neck down to a 2.5-inch pipe before exiting into an open 36-inch megaphone exhaust pipe. Each pipe thereby gets a firing pulse every 180 degrees of crank rotation (hence the nomenclature), and the venturi effect creates slight negative (4 psi vacuum) backpressure that increases output.© Provided by MotorTrend Long (36-38-inch) tubes connect two cylinders from each bank into each collector, creating all the plumbing crossing under the oil pan and requiring the front suspension to be hiked up slightly. These neck down to a 2.5-inch pipe before exiting into an open 36-inch megaphone exhaust pipe. Each pipe thereby gets a firing pulse every 180 degrees of crank rotation (hence the nomenclature), and the venturi effect creates slight negative (4 psi vacuum) backpressure that increases output.

1969 Chevrolet Corvette LT 2© Provided by MotorTrend 1969 Chevrolet Corvette LT 2
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