Nov. - Dec. 1999 Lane Racing And Rodding Article By Jim Kaekel, Jr.
Have you ever been "hanging it all out" heading for the finish line when you've suddenly felt like King Kong had grabbed on to your back bumper. King Kong showing up at your local drag strip is not likely to happen (we hear he's into skateboarding), but that sudden bogging down could have been caused by inefficient fuel supply. It's time you took a serious look at the fuel system, which consists of the fuel tank or cell, fuel pump, filters, pressure regulator, fuel lines, and fittings.
Unless prohibited by class rules, an all-out race car should be equipped with a fuel cell designed specifically for drag racing. Drag cells are filled with foam to prevent sloshing and have a sump at the lower rear with large AN-style outlet fittings to take advantage of the natural rearward flow of gasoline under hard acceleration. Cells are most often made of high impact plastic for superior safety in the event of a crash or rollover, and are offered in capacities up to 22 gallons. Cell manufacturers also offer mounting kits and most necessary plumbing fittings. Racers who run alcohol can also purchase alcohol resistant foam to replace the standard foam in the cells.
If class rules prohibit fuel cell usage, the stock tank can be suitably modified for a significant improvement. The tank should first be removed, cleaned and the original "sock" removed from the end of the pick-up. The sock was intended to keep larger debris from entering the fuel system but it is an unwanted restriction in performance applications.
A new pick-up tube can be fabricated from 3/8" or 1/2" tubing and extended to reach toward the rear of the tank so that it remains submerged, even under sudden acceleration. Several manufacturers offer a drag sump kit which may be welded into the stock tank to form a sump at the rear of the tank. The kits have 3/8" NPT outlet bungs to provide an ample fuel supply. CAUTION: Extreme care should be exercised when a stock steel tank is being welded. The build up of fumes in the tank WILL create a bomb when the welding begins. Leave this step to the professionals.
Before the fuel enters the fuel pump, it should pass through at least one non-restrictive filter to prevent pump damage. Fram manufactures a very high flowing filter with a replaceable element (#FRAHPG1) that is capable of flowing 90 gallons per hour at 5 PSI.
Fuel pumps, electric or mechanical, should be chosen carefully. Don't expect a high volume mechanical fuel pump to provide enough fuel for a 12 second drag car. Conversely, don't hang a 400 gph pump on that same car, because there is also such a thing as too much fuel. There are a number of excellent electric fuel pumps, usually complete with effective, easy to adjust pressure regulators, designed specifically for competition machines up to and beyond 600 horsepower. Shoot for a regulator pressure setting of 6-8 psi. Regardless of selection, any electric fuel pump should be mounted as close to the fuel cell/tank as possible.
While we're on the subject of electric fuel pumps, make sure the pump is wired properly. Too small of gauge wire, over the length of the car, is subject to a condition known as "voltage drop". This can prevent the pump from receiving the 12 volts needed for proper operation. Check the lead wire directly at the pump with a voltmeter while the pump is running. If there is a problem, a properly installed relay can correct it, and assure that the fuel pump receives adequate voltage.
Fuel lines should be properly routed to provide the shortest, safest route to the carburetor. Avoid exhaust components or any other source of heat. Frame rails and/or chassis tubing represent a reasonably straight safe path, where the lines can be secured with mounting clamps. Proper line size selection depends upon the horsepower, and the fuel pump manufacturer's recommendations. Original fuel line should be replaced with at least 3/8" aluminum tubing or -8AN stainless steel aircraft type hose for dual duty street/strip cars. Drag race vehicles that have in excess of 500 horsepower need -10AN stainless line. Fittings should be sized accordingly. Don't use hardware store fittings. They may be cheap, but they're restrictive...and downright ugly.