By now most people are aware that modern fuel -injected engines benefit greatly from the use of electronics, whether through the use of an on-board computer which constantly alters the tune depending on driving style, altitude or a number of other variables, or through the ability to plug in a laptop computer to make tuning changes. But in our little world the majority is still running carburetors and have in the past done our tuning with the combination of a screwdriver, seat-of-the-pants instinct and real-world testing on the street. Wouldn't it be nice to be able to know exactly what results you are getting from any tuning changes you make? It probably won't come as any great surprise when we tell you that you now can, thanks to the Fuel Air Spark Technology's (FAST) dual sensor air/fuel meter.
While there are a number of such meters available that allow you to see results from your tune-up while driving, the FAST meter has a couple of features that appeal to us. Its on-screen data logging means it doesn't require downloading the information to a laptop and its "Dual Sensor" capability means it can read data from both sides of a V-8, or any V-formation engine. This allows for more accurate carburetor tuning. An added bonus is that the kit is easy to use and simple to read--definitely a plus for the electronically challenged among us! The FAST meter can be used with computer-controlled engines and EFI, but it's carbureted motors we're interested in for the purposes of this article.
The FAST dual sensor O2 air/fuel...
The FAST dual sensor O2 air/fuel meter kit comes with a pair of O2 sensors, a lighted graphic display screen with built-in data logging facility, outputs for external data loggers, digital gauges, and a narrow-band simulator function that allows you to feed your engine's computer a factory signal while using the wide-band sensor for air/fuel measurement (not that we needed this on our carbureted engine). The meter takes its power from the vehicle's cigarette lighter to make it truly mobile.
So just how does the FAST meter work? It measures the air/fuel ratio, vital information not just for performance or economy tuning, but for anti-pollution reasons too. An optimum air/fuel ratio ensures a cleaner running engine as it offers the opportunity to achieve that perfect balance between being too rich or too lean. Modern factory vehicles with oxygen sensors automatically compensate for changes in the air/fuel ratio by analyzing exhaust gasses and adjusting accordingly, and the FAST meter works on this principle, letting the operator make changes to achieve the desired ratio, such as by changing jet sizes in the carburetor. This does mean installing a couple of threaded bungs in the headers or exhausts on cars not so equipped, in order to connect the O2 sensors. Hardly a major job, and they can be blanked off when not in use, but it does involve a little workshop time before the meter can be used.
Keen to put the FAST meter to the test, we hooked up with Westech Performance in Mira Loma, California to spend a morning at their facility doing just that. Our test mule for the session would be this author's '46 Ford roadster pickup. Hardly a performance combination, its 305ci Chevy small-block was rebuilt internally stock some 2,500 miles ago, but with headers, Pertronix ignition, and an Edelbrock Performer manifold. Running 87-octane gas, it's never going to win any drag races, but is perfect for what it was intended to be--a fun and useable pickup.
We were also keen to test Holley's new Street Avenger carburetor, as the truck had always seemed a little "flat" in performance, even given its mild motor. The aluminum Street Avenger is lighter than Holley's previous offerings, and lighter than the zinc Street Avengers too (it also stays brighter longer and is easier to polish!), has clear sight windows in the float chambers for easy float level adjustment, and comes already calibrated, as Holley's press blurb says, "Street ready out of the box."
So it was that we showed up at Westech one morning in March with the truck, a new Holley 670 Street Avenger and the FAST air/fuel meter kit. While the meter is designed to enable you to tune the engine at a cruise speed on the street, we strapped the pickup to Westech's dyno to simulate driving and make life easier on ourselves. Here's how the morning panned out.
In order to fit the O2 sensors...
In order to fit the O2 sensors we had to weld threaded bungs into the headers. Ernie drilled holes in each header and then MIG welded the bungs into the header collectors. We then installed the dual wide-band O2 sensors from the kit which measure the air/fuel ratio in both engine banks simultaneously or can average them together for precise tuning of carburetor jetting (or EFI profiles)
Holley's Street Avenger vacuum...
Holley's Street Avenger vacuum secondary series of carburetors are available with manual or electric choke, and in 570, 670, 770 and 870cfm applications. However, the aluminum versions, which weigh less than 8 pounds, are only available in 670 and 770cfm. All feature quick change adjustable vacuum secondaries and the Street Avenger fuel metering system, which is calibrated for "monster low-end torque, awesome acceleration, and unmatched top-end horsepower" according to Holley. Included with the carburetor are an installation and tuning DVD as well as a printed manual, gaskets, fuel line kit and two vacuum secondary springs, giving three different rates when you include the spring that comes in the carburetor.