Multiple inline carburetor setups date back decades, but gained mythical status in the heyday of the musclecar. In the Mopar world it was a "Six Pack" and Pontiac guys had "Tri-Power," but there was never really a catchy (or affectionate) name for Chevy's 348 W-motors or the '67-69 big-block engines equipped with three two-barrel carburetors. An air cleaner decal with a "3x2" designation was pretty much it. If it wasn't running properly, people cursed them as "Triple Trouble."
Truth was the trips generally looked better than they performed. Tuning was tricky and the vacuum-operated linkages used on the 427s Vettes often made for sloppy performance. Indeed, most engine builders discourage the use of these systems for those who want maximum performance, as a well-tuned four-barrel will out-perform them on the dyno and at the track.
Still, there's an undeniable "wow" factor that comes with a trio of inline carburetors. It looks exotic. It looks "musclecar." For some, that's all the reason they need. Carb wizard Barry Grant, however, has revisited the 3x2 idea with an eye toward serious performance, not just cruise-night credibility. To that end, his company designed the Six Shooter line of manifold and carburetor systems. And while versions for Pontiac engines and Chevy small-blocks have been out for a little while now, the big-block versions have just recently hit the market.
Actually, there are two versions for the big-block Six Shooter: one for rectangular-port heads and one for oval-port heads. Thinking such a setup would enhance the underhood appeal and, with luck, the rear-wheel output of his ZL-1-powered Chevelle, Michigan-based engine builder Chris Price elected to give the big-block Six Shooter a whirl. The car is a subtle, look-at-it-twice resto-mod that's powered by the same long-block GM Performance Parts used for the limited-run Ramjet ZL-1. To say the Chevelle is a slick piece would do a huge injustice to the word slick.
We tagged along and met Price and a few of his buddies from Retrotek Kustoms, of Howell, Michigan, at Flint's Hardcore Racing, where the intake swap and before/after chassis dyno tests would take place. Frankly, we were skeptical that the Six Shooter would make a substantial gain when compared with the engine's four-barrel induction system. "Three horsepower," we guessed-an educated guess based on years of experience testing bolt-on performance items.
The car was baselined on Hardcore's chassis dyno, where it made 343 hp and 348 lb-ft of torque at the rear wheels. It was a respectable baseline number, but to be honest we expected a little more from the 427 engine. After the baseline numbers were recorded, the manifold swap commenced.
We were generally pleased with the Six Shooter kit, which included the intake manifold, trio of polished Demon carbs, carb linkage, and an air cleaner. However, there were some details that puzzled us. The water neck on the manifold pointed straight ahead, whereas Chevy manifolds typically have angled necks. This design feature necessitated some creative hose cutting to make a workable upper radiator hose. Also, a boss and tapped hole had to be cut in to the front of the manifold to accommodate an electric fan temperature sending unit. This is a common feature on other aftermarket intakes and we'd wished Barry Grant had added it to its own when it tooled-up for the Six Shooter.
We also ran into some manifold-to-cylinder-head fitment issues. Slightly askew bolt-hole alignment meant some trial-and-error grinding to elongate the manifold's bolt holes in order to produce a smooth, snag-free run-down of the fasteners into the cylinder heads. The manifold used for our story was an early production piece, so there might still have been a few bugs to work out on the production line. In fact, we brought this to the attention of Barry Grant and we feel confident the issue has been addressed.
Finally, we were left wanting more from the instruction guide included with the kit. It's up to the installer to deal with the throttle cable/rod-to-carb linkage connection. It took more than a little time to modify the car's existing cable so that the connection allowed for wide-open throttle when needed.
Once the intake was installed, the linkage adjusted, and the timing set, it was back to the dyno where we were greeted by a foul smell and a 40hp loss. Yikes!
Of course, you'll have that when you, ahem, run the test car out of fuel on the dyno's rollers. Luckily, we were able to siphon some fuel out of Hardcore's racing supply and we were back to making full pulls.
Initial tests with the intake and no further tuning netted-surprise, surprise-a 3hp gain. But the air/fuel graph showed there was room for adjustment. Timing was adjusted to 38 and the engine responded with a noticeable gain. Final tuning adjustments delivered a total rear-wheel output of 358 hp and 376 lb-ft of torque. That's 15 more horses and 28 more lb-ft torque, or approximately 5 percent more horsepower and 8 percent more torque-not to shabby for a simple intake swap, we think.
The Six Shooter performed better than our initial expectations and definitely gives this big-block A-body a unique underhood appearance. This "shooter" hits the mark.