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Ask Anything - September 2014

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Just Fuelin' Around

Joe Rogerson; Ferndale, WA: I would like some advice on a fuel system for a '66 Mustang Fastback. I am installing a 363ci Ford Racing crate motor. Is the stock fuel line sufficient to supply a 500hp engine? Any advice or help would be fantastic. The drivetrain will be completed with a 9-inch rearend with 3.90:1 gears, a C4 transmission, and a 2,500-stall convertor. Have a great day.

Jeff Smith: This is a relatively new 363ci crate engine from Ford Racing that is based on the Boss 302 block using a great bore-and-stroke combination of 4.125-inch bore and 3.40-inch stroke using a Scat forged steel crank, rods, and Mahle pistons. This combines to create a 10:1-compression motor that's rated at 500 hp at 6,500 rpm and 450 lb-ft of torque at 5,300. It's got a hydraulic roller cam and raised-port aluminum Ford Racing heads. This sounds like a great small-block for a lightweight early Mustang. Assuming that the Mustang originally came with a six-cylinder or the standard 289 V8, these cars were equipped with a 5⁄16-inch fuel line. This is slightly undersized for a 500hp engine and there are people who believe that even a 3⁄8-inch line is too small, but we have years of experience with several cars running a 3⁄8-inch fuel line feeding both big- and small-block engines that make over 600 hp all day long, and we've never had a problem. Mustang companies, such as CJ Pony Parts, offer a pre-bent 3⁄8-inch steel tubing fuel line (PN MUF10030, $66.99) that would probably be the most economical. This steel line will be a little more difficult to install than flexible braided steel line, but the hard line will probably last the lifetime of the car. Our experience with rubber-lined braided hose is that it has a limited life expectancy. Apparently, current fuel blends using ethanol (predominantly E10—or 10 percent alcohol) is causing problems for these rubber hoses, and they tend to degrade rather quickly. We've experienced rubber-lined stainless braided line failure in as little as nine months. So taking the time to install a hard steel line would be advantageous for the long term. Another solution would be to use PTFE (polytetrafluorethylene, most often called Teflon, a DuPont brand name) fuel hose lining that is impervious to all kinds of fuel (including straight methanol) and would basically last as long as necessary. The problem with PTFE fuel line is that it is expensive. Companies like Aeroquip, Earl's UltraFlex 650, TechAFX, and several others offer this hose. It also requires specific hose ends that are not interchangeable with typical rubber-lined braided hose. While expensive, unless the hose is damaged, it should last the life of the car. I've used the TechAFX hose on my '65 El Camino when we converted over to EFI and also on my Orange Peel Chevelle.

While we're on the subject of fuel flow, this leads us to the question of the design of the fuel system. The simplest system for a carburetor is a single fuel line using a mechanical pump. We looked into a Holley mechanical pump and found that (according to Holley's published fuel rating) the Street Avenger pump PN 12-289-13 is rated at around 530 pounds of fuel per hour (lbs/hr) at 4.5 psi. Assuming the industry standard 0.50 brake-specific fuel-consumption number—which is pounds of fuel per horsepower per hour (lbs/hp/hr)—by dividing the horsepower by 0.5 (which is the same thing as multiplying horsepower by 2), you can determine how much horsepower this pump can supply in terms of pounds of fuel. To feed 500 hp, you would need the equivalent of 250 lbs/hp/hr. The Holley pump is rated to deliver roughly 530 lbs/hr of fuel at 4.5 psi, so it should be able to deliver all the fuel you need.

If you are considering eventually moving up to something more exotic like EFI or even a blow-through supercharger, then a more sophisticated fuel-delivery system is probably warranted. At that point, I would seriously consider a return-style, fuel-delivery system. You could probably use the original 5⁄16 fuel line (if it's in good shape) as the return line with the steel 3⁄8 as the delivery line. This would allow you to use an in-tank electric fuel pump. Today, nearly all new cars use turbine-style, in-tank electric pumps and can deliver a huge amount of fuel considering their small size. My current favorite system is the Aeromotive Phantom system (PN 18688, $537.97, Summit Racing). We did a complete installation in my '65 El Camino ("The Phantom Knows," Oct. '13) using a new fuel tank from OPGI modified to accommodate the fuel pump, and it works very well. With a return-style system, the pump does not have to work nearly as hard because any fuel not used by the engine is returned to the tank. The Phantom uses the Aeromotive Stealth 340 pump that can push more than 100 gallons per hour at 15 psi, which equates to 620 pounds per hour of fuel, which is more than enough to cover 1,200 hp should you need that much fuel. At higher EFI fuel pressures, this capacity is reduced somewhat, but it's still capable of feeding 700+ normally aspirated horsepower. There's not a smaller pump version using the 200-lph pump that will easily feed 600+ hp. The 200-lph Phantom pump kit is PN 14689 ($439.95, Summit Racing).

Just for fun, we plugged your Mustang with this engine into the Quarter Pro simulation. We had to estimate the torque curve and vehicle weight at 3,100 pounds. With a 26-inch-tall rear tire, the simulation says your Mustang could run 11.30s at 122 mph. This is just an estimation and includes a conservative 1.80 60-foot time. With a looser converter and good traction, your Mustang could run very low 11s. This sounds like a great way to spend a Saturday night.

More Info

Aeromotive; 913/647-7300; AeromotiveInc.com
Aeroquip; 800/386-1911; Eaton.com
Holley Performance Products (Earl's); 270/781-9741; Holley.com
CJ Pony Parts; 800/888-6473; CJPonyParts.com
TechAFX; 877/355 0137; TechAFX.com

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