As stock car racers, we often fall into the trap of believing that as long as the engine idles and runs at full throttle, the carburetor is giving us all it's capable of. The reason cannot be a fear of complexity-not compared to the problems of determining roll centers or measuring dynamic caster gain, which most racers handle with no problem. For some of us, it's because we concentrate solely on tuning the suspension and leave everything between the air cleaner and the oil pan to the engine builder. For others, it may be because we've given a custom carburetor builder $3,000 to tweak a stock carburetor within an inch of its life, and now we are afraid to touch it.
Regardless of the reason, if you fall into this category, you may be missing out on the track. When tuned properly, a carburetor can be used to help control how fast the engine puts the power to the rear wheels and, in essence, becomes a legal traction device. This is true regardless of what brand you are using.
According to Barry Grant's Doug Schriefer, tunability is the key: "If you race the same track every week, and your setup is pretty good at getting you through the corners, but you are getting too much wheelspin, it doesn't make sense to start automatically swapping shocks and springs. If your setup is good, then leave it. Let me help you control the wheelspin coming off the corners with the carburetor."
Since it began manufacturing its own line of performance carburetors in the early '90s, Barry Grant has concentrated on giving the racer lots of tuning options in its line of Demon carburetors that can be performed easily and quickly. Granted, many circle track stock car divisions require a specific Holley part number, but if your track or division has no restriction on the brand of carb you can run, a Demon carburetor should at least be considered.
Because it shares most of its basic architecture with a Holley carb, a Demon isn't an alien piece of technology for most racers. We're still talking about boosters, venturis, float bowls, and throttle plates in all the positions you would expect. The differences are finer, but they may turn out to be quite important to you on the track and in the pits.
One of the newest advancements Barry Grant has added to its Demon line is a unique set of quick-release throttle cams that allow you to tune how quickly the secondary butterflies open up. Known as the Traction Master baseplate assembly, this can be quite useful on slick tracks or in divisions where the engines are more than a match for the tires. On a high-bite track, where you have all the traction you need, use the 1:1 cam that opens the secondaries normally. But on a slick track, where hooking up the rear tires on turn exit is a problem, you can switch to a throttle cam that delays the opening point for the secondary throttle blades. The effect is to give the driver the feel of a longer throttle pedal. Many drivers believe they can be gentle enough with the throttle pedal to keep wheelspin to a minimum regardless of the track conditions, but few are actually that good. Schriefer says almost every driver he has worked with is able to improve their lap times using the Traction Master baseplate assembly, because less wheelspin means more forward bite, and more forward bite means better acceleration on turn exit.
According to Schriefer, the Traction Master is becoming popular among dirt track drivers, many of whom change the cams between qualifying, heat races, and the main event. During qualifying, when the track is normally fresh and tacky,a 1:1 cam may do the best job. As the track sees more laps and dries out, the racer can change to a 30 percent and then a 60 percent cam that delays the opening of the secondaries to help him control wheelspin when he first picks up the throttle coming out of the turns. Schriefer says it won't turn a club-footed driver into a series cham-pion, but it will help an intelligent driver become more consistent and faster, lap after lap.
Other Demon innovations include a billet baseplate that eliminates the porosity commonly found in cast pieces and reduces the chance of breaking an ear off the baseplate from overtightening. The metering blocks on all Demon race carbs are also billet pieces. Schriefer says the porosity caused by casting the metering blocks can mean a bubble or imperfection in the metering circuits, which will cause a tuning problem. It won't be immediately obvious, and a bad metering block can leave a racer scratching his head for weeks over an engine that won't behave quite right. Machining the blocks from billet eliminates this possibility. The feature list continues with pedal stops built into both the primary and secondary linkages instead of the much more fragile throttle shafts, external butterfly adjustments, and even an air bypass system that allows you to tune the idle rpm without drilling holes in the butterflies.
The result, says Schriefer, is a carburetor that may cost slightly more off the shelf than the com-petition, but already has tons of tunability built in. In many cases, a Demon won't need to be extensively reworked by a carb tuner, which can save the racer tons of money in the long run. Saving a little bit of money while possibly going a little bit faster is what we are all about.
The Check-Legal Advantage
While Barry Grant's Demon carburetors have taken off in drag racing and most other forms of performance motorsports, they really haven't gained much of a foothold in stock car racing. That's not because they won't work in oval track racing. Rather, it's because many tracks and sanctioning bodies specify in their rules the exact carburetor brand and part number that must be run. It was a rudimentary attempt to keep costs down, but the effect of these carb rules is to subsidize an industry of specialized carb builders that take the stock piece and completely rework it for sometimes outlandish prices.
In an effort to give racers another option, Barry Grant includes a Check Legal line of carburetors in two- and four-barrel forms specifically for circle track racing. "We're looking to be an option for both the racers and the tracks," explains Demon's Doug Schriefer. "We aren't trying to force anyone to run our carburetors or anyone else's. Our 650 four-barrel flows the same amount as the competition's 650. We aren't trying to sneak in extra performance on the sanctioning bodies. We are just trying to give the racer more tuning options and the tech man a few options instead of declaring a carburetor illegal and throwing the guy out."
What Schriefer means is that features such as easily removable venturis and boosters will allow a racer who was found to be not quite legal to still race instead of going home angry and leaving a smaller field for the fans. For example, if a tech official sees a booster or venturis modified in a way he doesn't like, he can require the racer to replace the booster or venturis with a set the track owns. The racer has the option to still race, the track gets back its boosters or venturis at the end of the night, and the tech official can send the questionable pieces to Barry Grant to be checked out.
We also were interested to see how the Demon carbs checked on a standard set of carburetor tech gauges. Most tracks use a set of Go/no go gauges such as these. As we saw, the same gauges work on Demon carbs the same as they would on a Holley unit.
