The Predator carburetor can...
The Predator carburetor can be intimidating, but it's really very simple because fewer parts are involved.
Most everyone in racing has at least seen a Predator carburetor-the unique box-shaped variable venturi carburetor that has been around since the '80s. You may be surprised to learn that the Predator has a small but growing legion of users, including a number of IMCA Modified and Limited Sprint competitors.
The interest in the Predator has been stimulated by the conversion kit for use with methanol. The benefits of running alcohol include improved power potential, better cooling, and savings on expensive racing gas. Of course, the fact that the Predator differs significantly from the standard Holley has caused many a racer to steer clear of the unit because of unfamiliarity and lack of tuning experience. In reality, the Predator has a fraction of the parts found in a Holley and is really quite simple to tune and maintain. The Predator does not employ jets but uses a unique "cam" setup that allows for a variable, easily adjustable fuel flow. Combine this with the variable venturi design (it flows from 390 to 930 cfm, depending upon engine demand), and you have a different approach to the science of air/fuel distribution.
One of the Predator's strongest proponents is the team of Danny Gwynn (owner), Ronnie Vernon (driver), and Dave Kawell (engine builder). They've been a major force in IMCA-type Modified competition in western Tennessee for a number of years and have won several track championships. According to Vernon, the Predator's strong suit is its throttle response, which enables him to come out of the corners quicker.
Here's a side-by-side comparison....
Here's a side-by-side comparison. On the left is a used gasoline model, and on the right is a new alcohol model. The used gasoline model can be retrofitted for alcohol with a do-it-yourself kit or by sending it to the New Jersey office.
Another point to consider is the Predator's price. While a brand-new, out-of-the-box Predator typically retails for $799 (in line with other brands), real savings can be had by picking up a used gasoline Predator (PX-6000) at a swap meet or on eBay for $100 to $200 and converting it to alcohol. The conversion kits are available for around $288 (retail), or the old carb can be sent to Predator's New Jersey facility and retrofitted there. The cost is under $400 for parts and labor (which includes bench-flowing the carb and setting it up to the customer's needs), with the only real difference between that and a new alky Predator being the black anodized body, which can also be done at the retrofit time for an upcharge.
What's different about the alcohol Predator? Because the volume of fuel required to support combustion is greater with methanol than gasoline, the carb is retrofitted with an extended fuel bowl (which doubles the capacity) that has an extra inlet. Inside the Predator a special distribution block and nozzle bar are added. There are some minor circuit modifications to handle the extra flow. That said, the conversion is a fairly straightforward affair that requires only a drill and handtools.
All in all, the Predator, store-bought or swap meet special, represents an economical and effective alternative to the norm. Given the cadre of competitors that swear by them, the Predator is clearly something that merits consideration by racers in those classes where they are allowed.