The Stromberg 97, and its siblings, the larger 48 and more diminutive 81, are arguably one of the most popular lines of carburetors among hot rodders ever produced. While the Carter AFB, Edelbrock, and Holley four-barrels have definitely taken some of the wind out of the Stromberg's sails over the years, the faithful have stuck to the old two-barrel jug for everything from stock Flatheads, their original motor of intent, to fire-breathing, Nitro-drinking, tire-smoking dragsters. Getting more fuel and air into the engine was the name of the game and guys have been using the old carbs for just that since the late-'40s. Since then, they've been used to emulating the setups run in the early days of hot rodding but their rise in popularity has likewise caused the demand, and therefore the price, to rise as well. And with the availability of decent, rebuildable cores steadily on the decline over the past 10 or so years, it's getting harder and harder to build a reliable multiple carburetor setup. Until now.
Speedy Bill Smith and his crew at Speedway Motors in Lincoln, Nebraska, have been catering to the hot rod and racing market for over the past half century, providing parts and service unequaled in the aftermarket world. From suspension parts to rolling roadster kits, to say that they've kept the proverbial hot rod torch burning all these years would be an understatement. They've managed to keep their finger on the pulse of hot rodding , so it should come as no surprise that they saw the writing on the wall when it came to the dwindling Stromberg resource.
That's when they decided to step in and do something about it by introducing a 100 percent completely new carburetor based on the legendary Stromberg 97. Dubbed the 9 Super 7, the old 97 has been reproduced to the closest legal allowances and is everything the original Stromberg 97 is, was, and then some.
Aesthetically, the 9 Super 7 is nearly identical to the stock unit, minus the large 97 logo that graced the side of some of the older jugs and the patent numbers commonly found on the float bowl area. They've also upgraded some of the internal bits, notably the float, needle, and seat. Jetting and power valve settings remain as they were for the original 97 carbs as well as the cfm and vacuum specs.
The other similarity that the 9 Super 7 shares with its antique counterpart is the setup and tuning necessary to yield a well-running machine. While perhaps not as simple as bolting on a single four-barrel, the 9 Super 7 makes setting up a multiple carburetor induction system easier than when Strombergs were available new. All that's required is an intake, a linkage system, a Uni-Syn syncing tool, and a little patience.
We've been working hot and heavy recently on our project '55 Chevy that will soon be gracing these very pages with an assortment of tech stories and decided that it would be the perfect guinea pig for a trio of Speedy Bill's new carbs. Equipped with an Edelbrock Victor Jr. intake manifold topped by a 750-cfm Edelbrock carb, the little 327ci engine lacked both low-end torque as well as curb appeal when it came to the engine compartment. And with fuel prices being what they are, the thought of cruising around on a single two-barrel with a pair of secondary carbs at the ready when warranted, a tri-power setup was just too hard to resist.
We started out with a trio of Speedway's 9 Super 7 carbs, all set up with their idle circuits intact, before contacting Edelbrock for a 3x2 intake and fuel block. A progressive linkage kit was also picked up, provided by Eeelco, that will allow the carbs to be set up to open progressively, with the center carb operating as the primary and the outer two operating later as secondary carbs.
Here's the new carb, fresh...
Here's the new carb, fresh out of the box. Speedway ships them only after a flow test and leak inspection has been done to ensure trouble-free installation. The choke assembly, accelerator pump, and jets have all been faithfully retained and accept standard Stromberg parts.
While entertaining the notion of installing a tri-power setup, we decided to upgrade a few items underhood, for performance and aesthetic purposes. The first was the stock distributor that had been outfitted with an early points-conversion kit over 10 years ago. We saw Retrotek Speed's new Powerfire adjustable timing distributor at the '08 SEMA Show, where it won First Place in the "Best Engineered" category, and just had to give it a try. Adjustable in increments of 1/2 degree, the timing is easily manipulated with a turn of a button. To complement the Edelbrock intake and fuel block are a pair of their finned aluminum valve covers. Accel Ignition just introduced ceramic boot spark plug wire kits available in 180-, 90-, and 115-degree styles and we liked the idea of saving our boots from header heat. The stock ram's horn manifolds just weren't cutting it anymore so we slapped a set of Doug's Headers '55-57 Chevy mid-length headers on with the Metallic Ceramic Thermal Barrier Coating option to ensure they remain prettier than the rest of the car. With such a cool induction system now installed, it'd be a sin to kill the vintage vibe with a modern, one-wire alternator, but generators have never had a reputation for being entirely reliable. Enter Powermaster Motorsports new PowerGEN one-wire alternator. Hid in a generator-style housing, it provides the look of a classic generator with the output and reliability of an alternator. Not pictured but worth mentioning is Powermaster's line of high-torque starters (we used one from their Mastertorque line), good for 180 lb-ft of torque.
Setting up the carbs proved easier than I thought, and just as Speedway advertises. Once we got the primary carb adjusted to provide sufficient idle to keep the engine running, it was a simple dance between the secondary carbs with the Uni-Syn and a screwdriver to adjust their idle settings. Back and forth between the three carbs got them all in sync while keeping the idle at a reasonable rpm (we had it down below 800 rpm and it ran like a clock). About 20 minutes after bolting the carbs down, we had them tuned and were running up and down the local "strip" smiling with glee every time those secondary carbs came on, bringing with them a sudden rush of acceleration, and that "whoosh" of air as six barrels of carbureted fury suck air and fuel into the engine. To be honest, we expected to need to adjust the air/fuel screws a bit to really get it to run right and never thought that getting the three carbs adjusted in unison would be so easy. The thought of a bolt-on carburetor ready-to-run out of the box based on a 70-year-old design just doesn't seem possible, but it did, and I did it. And if I can do it, Speedway must've made a REALLY nice product, because I can't usually tune a radio let alone a carburetor.
We dyno tested the Speedway 9 Super 7 carburetor back to back with an original Stromberg 97 on a 355ci small-block Chevy. Both carburetors performed equally well, with comparable power. The 9 Super 7 delivered a slightly richer fuel mixture than the stock 97-which is a good thing with today's poor-quality pump gas. This is a smooth carburetor-it does everything right. I think it is a very good piece.
-Earl Gaerte, Race Engine Builder, Gaerte Engines
We tested the 9 Super 7 on Bob Everts' '32 Ford sedan delivery, which has a stock '36 Flathead V-8 previously equipped with a Stromberg 97. We removed the Stromberg and installed the 9 Super 7. We hit the starter and it fired up immediately on a cold, unstarted engine. It idled perfect with no adjustments or leaks. After a short drive, we shut the car off for a few minutes; it restarted immediately upon engaging the starter button. Overall driveability was excellent. Bob has kept the 9 Super 7 on his '32 and reports that it is still running great.
-Jackie Howerton, Race Car and Street Rod Builder, Former Indy Car and Sprint Car Driver
Here's a bird's eye view of...
Here's a bird's eye view of the float bowl and venturis. Speedway kept to the original Stromberg specs of a 0.97-inch venturi diameter but upgraded the float to a neoprene unit.
The biggest upgrade, however,...
The biggest upgrade, however, was made to the troublesome needle and seat inlet, replaced by a Grose jet inlet valve. This valve better copes with higher fuel pressures, improves high speed running, and won't stick or dribble like the old viton-tipped needle and seat setups. The Grose jet valve also won't corrode in modern fuel, something the original needle and seat units could be known to do.
The 9 Super 7 carbs are shipped...
The 9 Super 7 carbs are shipped with a No. 65 power valve, identical to the stock 97...