Currently we are working on a brand new prototype carburetor with Quick Fuel Carburetor’s. We had these carb’s on display on Tony Raffin’s Top Sportsman engine at the 2008 PRI Trade show this past December in the Land and Sea Dynamometer display. Quick Fuel has tooled up to make its own 4500 series (Dominator) main body. This is not a warmed over version of the existing 4500 main body. There are substantial changes to make this a “New and Improved” carb. The single biggest improvement of the new casting is its longer main venturi. This longer main venturi will create a greater signal to the booster venturi. This longer main venturi will also allow a greater flexibility in placing the booster venturi. The new Quick Fuel main body also has a .300 raised section at the opening of the venturi. This raised area helps straighten the air as it enters the main venturi. If you have ever flowed a cylinder head it is similar to having a radiused entry on an intake port when measuring head flow. In the center of the main body there is a rasied contoured area that should help equally distribute the air equally to all four venturi’s. The new Quick Fuel main body also features a completely adjustable external throttle linkage. Not only does this eliminate the potential of linkage coming loose and ending up IN your engine. The easily accessible linkage can be “tuned” for street driving or a more progressive application of power on a marginal race track. The new main body is also available in a large selection of main venturi and throttle blade sizes. What this means is Quick Fuel will be able to offer an “off the shelf” carb with a 2.25” throttle blade. Depending on Booster and main ventuir combination this means a 1500+cfm carb will be no problem. The new main body is a very high quality casting that is visually very sleek and has a real art deco feel to it.

Traditionally one improves engine performance by making things bigger: Bigger camshaft duration, bigger cylinder heads, bigger intakes, of course bigger carbs. All of these bigger components kill air speed and “signal” to the carb. You can improve “signal” with a number or parts like sheer plates, stepped boosters and intake modifications. Unfortunately all of these “cures” for a weak signal are curing the symptom not the problem. A carb with a longer main venturi will make a greater signal for the booster venturi similar to how a collector extension helps create greater exhaust signal.

We recently tested some of these carbs on a 645” Predator engine with 15.5 compression, .895 lifter roller, sheet metal tunnel ram w/2x4 1150 Quick Fuel Marvinator’s (we’re not sure if that is the name, we just call them that) and a wet sump oil system. Initial testing was very positive, we would make small changes (.002-.003) in either the high speed or intermediate air bleed and see significant power changes. Normally big intakes, cams, carbs will tend to have a weak cylinder or generally not be very responsive to small changes. The new Quick Fuel Marvinator’s responded very well and actually pulled too much fuel at higher engine speeds. The engine would maintain a very flat 12.9-13.2 A/F ratio right up until 6600 RPM’s. At that point the engine would flat line and go to 12.0. It would maintain this 12.0 A/F ratio and not make anymore power. The engine made 1272 HP @ 6700 and 1006 torque @ 6300. We conferred and agreed that the reason the engine went “fat” was not a cam or intake issue but that there was too much fuel coming thru the booster that we could not tune out with air bleeds. A lest efficient booster (shape and size of holes in the actually booster) should cure our “fat” condition.

We had a great time with Marvin and Derrick from Quick Fuel during their time at our shop while testing. Their insight and knowledge was immeasurable and greatly appreciated. They are sending us some different boosters and a set of 1250’s to try ASAP. I’ll let you know how it all turns out once we get it finished.

Mike @ MM