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Looking Back at the Motion Performance Big-Block Vega

The Motion H-bomb kit

Ro McGonegal Feb 12, 2019
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In the beginning, before the Internet or anything like it, hot rodding was an exclusive community that revolved around a simple premise: putting bigger power where not much used to be. Ordinarily, a small, light vessel would be the recipient. There was no nitrous, no popular idea of any kind of “power-adder” beyond the massive GMC supercharger. Then, people didn’t call such device a power-adder or anything of the kind.

Once upon a time, Hot Rod scored an exclusive tech story straight from the Chevy product planner’s teaser book. Those engineers were always busy boys, concocting and producing succulent what-if combos that were guaranteed to make enthusiast press wanks drool and stutter. This time, the item was a Vega fitted with an all-aluminum 302 V-8 and a Turbo 350 transmission. It ran a 13.97 elapsed time, as reported in the July 1972 issue. Nothing more came of it.

002 Motion Performance Big Block Vega 2/6

1973: the odd-even day oil embargo did its best to consternate everyone, but hot rodders are always gonna hot rod and one of the most progressive conversion houses was Motion Performance hard by Sunrise Highway in Baldwin, Long Island. After nearly a decade of amassing an army of big-block soldiers (Corvettes, Chevelles, Camaros, and Novas), there was one source yet to be tapped: the hapless, heinous Vega. Extant for nearly four years, there was a sea of chain-whipped H-bodies with their panting, leaking four-bangers hanging out like an overheated dog’s tongue.

But long before ringmaster Joel Rosen gave it the big-block swap, he’d converted many Vegas with a 350. He admitted that the big-block idea wasn’t completely his. “Ever since we’d started swapping the 350 engines, the Rat motor requests had been outrageous. I had people calling constantly for the availability of just such a piece. So as soon as I was certain of the market, I decided to build the car and offer a complete kit from the first prototype.” Specifically, that was the car I drove in the early fall of 1973. The story appeared in the January 1974 issue of Car Craft under the title “King Kong is Living on Long Island.”

As a preface to this episode, several months earlier for another Car Craft assignment I had lived a week with an LT-1 conversion that Scuncio Chevrolet in Greenville, Rhode Island, was marketing. It suffered from a suspension system that was too tightly bound and brakes that flat didn’t work well, even when there was no hurry. The Vega and I sailed straight through more than one big red stop sign. Beyond that, the ghost Vega was utterly reliable and worked as it should have. You just had to pay attention, keep your wits about you.

003 Motion Performance Big Block Vega 3/6

At this time, the 1970 Clean Air Act—abetted by the EPA and the DOT—the stringent fuel situation, and opposing voices from the public at large combined with gelded engines, awful energy-absorbing bumpers, and the suborning of high-performance options. The implication was a cold, featureless future. This didn’t bend Rosen one bit; he merrily continued, dropping small-block V-8s in his Super Vegas for three years.

In their crusade to snuff the proliferation of “illegal, unsafe, modified” high-performance cars, the Department of Justice revenuers had come across the King Kong opus, and meaning to set a precedent, threw a hammer-lock on Motion, ordering it to cease and desist. In the spirit of the law, they gave him a noogie, levied a nominal $500 fine and stipulated that all modified new vehicles (not just Vegas) would forever be export only; the preponderance of these mutants wound up smoking their big, fat tires in Puerto Rico, Iran, and the United Arab Emirates.

In reality, Motion was working with the integrity of a Dixie cup never meant for the girth or the output of a V-8 engine, never mind an all-iron Mark IV engine. To ensure the conversion, it needed surgery and chassis upgrades that posed giant warranty problems and legal liabilities, so none of Rosen’s usual dealership contacts wanted anything to do with it. Though the small-block conversions were readily accommodated with selective use of a hammer and a 2x4, the big engine needed some surgery in the bellhousing region to situate the 454 in the “stock” location.

004 Motion Performance Big Block Vega 4/6

Logistics were painful. The breadth of the engine and the tube headers (built by Motion) scotched traditional side engine location, so they fashioned a saddle-type front mount reminiscent of the ’62 and earlier Corvettes to position it. The back of the module was supported by the same tubular transmission mount in the standard 350 Super Vega conversion, but it was located an inch farther to the rear.

Motion provided a raft of enablers. The primary kit contained the motor mounts and the headers. The deluxe ensemble included those pieces as well as hoses, belts, pulleys, and front springs with the same free height as stock but with thicker wire diameter. A stock Vega posed a 53.2/46.8 percent weight bias. With the big-block lard hanging over the front wheels, what do you think the spread was with an additional 400 pounds up front (Vega aluminum four-cylinder: 285 pounds; all-iron big-block: 685 pounds)? It had Koni adjustable shock absorbers and an 18-inch diameter Flex-O-Lite fan. Sure, there were options: a heavy-duty cooling core, a narrowed 12-bolt, and a shorter prop shaft. On top of this, you had to have the stock discs drilled for a 4 3/4-inch 5-lug pattern (in this case to accept 14-inch Cragar S/S hoops and F70 tires). The Vega’s brakes worked like the ones on the Scuncio car, only worse.

They located the axlehousing with the original coil springs and substituted boxed channel stock for the upper and lower control arms. The N50x15 Goodyears (28-inches tall, 12.6-inch section width) and stock-width 12-bolt posed another glitch. The tire tread surpassed the fender lips and, to my mind, denigrated the enterprise. They really needed mini-tubs and a narrowed axlehousing to contain them, but the revenant we drove was rigged with Gabriel HiJackers to lift the body above the tires and they were real good at limiting suspension travel.

005 Motion Performance Big Block Vega 5/6

More than 40 years after the fact, all I have to go on is what I wrote, the gleanings of perhaps a two-hour stint on a hot afternoon. I also wrote some crap about the car being hurried to “completion” for our magazine deadline. Thinking about it now, it was more a case of me excusing Motion for a car that should have had a narrowed 12-bolt at the least.

The Motion hood looked cool but wasn’t necessary for carburetor clearance. It would have been better served with vents to mitigate heat. That expression “ten pounds in a five-pound sack” sat on me like a vulture; a better band-aid would have been to vent the inner fenderwells to allow the super-heated air to escape that stifling five-pound sack.

A half-hour into the traffic and stop lights, mostly on Sunrise Highway, the Rat puked coolant, but not enough to curtail the investigation. The stiff control arms nulled wheelhop but, of course, did nothing to curtail the (4.56:1) wheelspin that punctuated every gear when I banged the BorgWarner. Later, Rosen admitted that the best transmission for the car would have been a Turbo 400.

006 July 1972 Hot Rod Magazine 6/6

Considering the dubious weight balance and manual steering, I was hesitant to slam the Vega into a corner for fear of monstrous understeer. But on cruise, the load felt well placed. The big-block Vega felt just as contained as the small-motor version I’d driven, but then I was only peddling it steady-state and in a straight line. The consternation was the exhaust. Since there wasn’t enough real estate underneath the forlorn H-body, Motion routed the blast through side pipes that exited right below the driver’s head—all the 350 conversions had their exhaust systems completely undercar.

At the time of this “test” the King Kong Vega was one of a kind, though Mr. Motion said he was sure that there were three of them … and perhaps a fourth cobalt bomb, as well. What was the price tag? He stopped for a long moment and said it started at $4,000 and went to $6 or $7,000 US dollars. Did he know the whereabouts of any of them? No. About the overheating proclivity? He tried his best but the thicker radiator core created for the swap and the Flex-O-Lite fan—originally for an air-conditioned application—were not really enough. Motion built the initial tubular exhaust headers but if the project rocketed, he said he’d already made arrangements with a major source to handle that chore.

So what about that vulture on the bedpost? With a bit of exasperation in his voice, Rosen said, “I hate to think about that car now.”

About the Author: Ro McGonegal began in this business back in 1968. He’s been editor of Car Craft, Hot Rod, and Chevy High Performance. He’s a wealth of old-school knowledge and his stories from “back in the day” are epic.

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