Like the air around us, the spectacle of a GMC 71-series supercharger on a V-8 engine is so familiar that we don't even bother to question its origins. It's just one of those things that always existed, as if on the seventh day, after making water and earth and so on, God used his day off to bolt a Jimmy diesel blower to a bent eight. "And then there was torque!"
But the thing that inspired so many generations to bolt a Roots-type GMC blower on an engine does in fact have-no pun intended-roots. And to be honest, those roots aren't really that long. To the best of our knowledge they go back 63 years, when a slight man with very big ideas bolted one of those massive blowers to a diminutive engine-a Flathead of all things.
In fact, those roots may well end at this very car. Legally it's Scott Perrott's nowadays, but he's the first to admit it is, and will forever be, Barney Navarro's. Navarro, if you don't know, was the hot rod's Renaissance man. When he died in 2007, he left a legacy so purposeful that it even made his death seem calculated (he shut off his internal milling machine on August 20, his 88th birthday).
For starters, when most aftermarket cylinder heads were little more than milled versions of stock ones, he developed his based on shapes that promoted gas flow and flame propagation. He applied that same independent thought to manifold design by optimizing their runners based on firing sequence and flow dynamics-a big deal when the typical hop-up manifold was nothing more than a stock item with a few extra holes poked in it.
But it was his unheralded achievements that really marked Navarro a true thinker. Among other things, he dabbled in oxygen injection and milled a manifold plate that used the engine's inrush of air to condense fuel. Adhering to a methodical system, he affirmed, debunked, and discovered ideas. "He was one of those guys who would say, 'The scientific principle of this is...' and he'd come up with this long dissertation that would lose you three sentences in," Scott noted. So Barney Navarro was a scientist. This was his laboratory.
By all accounts, it ('27 T) shouldn't be here. For that matter, it looked as if it shouldn't have existed in the first place. Though it eventually evolved to the way it appears now, "There's a picture of the car and it looks just terrible," Scott noted. "On the back it says 'Built in four days; refinements came later.'" The photo, which was taken in 1948, shows Navarro leaving the line at Muroc Dry Lake. The car's finish shows an absolute lack of regard and the lettering isn't much better. It appears that he cut the hole for the pitman arm with a can opener. There's another hole in the hood, only this one has four carburetors poking way out of it.
The car's appearance wasn't calculated, but it spoke volumes: Navarro could give a rat's ass how things looked; he cared only about going fast, which he did ... most of the time at least. In fact you could make the case that Navarro really didn't care about going fast on a consistent basis as much as he wanted to go really fast to prove a point.
It all goes back to the idea that Navarro's car was a testbed. And to illustrate that, refer to that photo of the hastily built car leaving the line. Though it looks the part of a lakes racer, Navarro actually built it for more than that. Take the pitman arm: it's on the right. "The reason is if you break a tie rod you can still steer the car," Scott explained, noting that the right-front wheel is the one that actually directs the car when it's pitched sideways and going left. The belly pan shape suggests that the car saw track duty, but those high-mounted carburetors left everybody scratching their heads.
Lakes racers did dabble with superchargers, but they usually stuck to the early centrifugal Frenzel or McCullochs. If they used Roots-type blowers, they stuck to the small-displacement Italian S.Co.T. superchargers with few exceptions, like the prewar Benz blower that Don Blair once used. The thing common to all of those was they weren't big enough to push enough air into the engine, let alone push the carburetors through the hood in such dramatic fashion. And about the only superchargers familiar to roundy-round racers at the time were on Offys and Novis, and both of those were way out of a dirt-slinger's league anyway.
"The car was originally built to run CRA," Scott explained. While the association did in fact permit superchargers, it made them seem too bothersome to run, which explains track racers' indifference to them. "They had a rule that if it was a blown motor it could be only 181 inches," Scott concluded. And that's where this odd duck gets even stranger: Navarro used an 85hp Flathead, an engine that even in its smallest displacement was 40 cubes too large for blown CRA racing.
By the end of the war, the 85hp Flathead was the small-block Chevrolet in just about every form of racing. They were everywhere, and as a result of their abundance racers had no qualms about blowing them up in the quest to go faster. So you could say their faults were pretty well known. Because of Midget racing, so too were the faults of the V-8/60 known-only that engine was nearly 50 cubes shy of spec and leagues behind its 85-horse brethren as far as duty cycle went.
In simple terms, Navarro de-stroked it. Now stroking or de-stroking an engine to alter its displacement is as common as air ... or a Jimmy-blown V-8 for that matter. But the extent to which Navarro went wasn't ... or at least wasn't at the time. To reduce the engine's displacement to that degree, he machined a 3-inch-stroke crankshaft ... from a big block of steel. And here you thought billet was high-tech modern.
Though Navarro campaigned the car in both dry lakes and dirt track venues, and though the car went well and set a few records, consistent success eluded him. For starters, "[Navarro] was a terrible driver," Scott lamented. He did have the humility to hire drivers, including Walt James, who's the only one still alive who drove the car. According to Scott, "[James] said, 'Man, it had more horsepower than you could believe'.
"[James] actually put it in the (trophy) dash, and that's probably the only time it ever made it," he explained. "What [Navarro] bitched about was that these guys that he got as drivers wouldn't push the engine. He said it would turn 8,000 rpm. I didn't believe that-I didn't believe it for years," he admitted, citing the three main bearings that usually limit the engine's potential.
"But see, he de-stroked it and used a 180-degree crank, so it was really stiff and it would turn those rpms, especially with that blower," he continued. "[James] said the thing would absolutely scream and it would just scare you to death. The engine's turning too fast, you've got the blower noise, and you've got the rearend making noise behind you. Most of these guys were used to 5,000 rpm tops and wouldn't stick their foot in it."
The results were equally mixed at the lakes. At the '50 Bonneville Speed Trials, Navarro's car set the fastest time in B/Roadster by running 146.81 mph, however, engine damage the car sustained during that run prevented Navarro from backing it up, which would've let him set the record. "So he's out," Scott said.