Ford 390 FE - Build A Low-Buck Street/Strip FE

Fitting the strip engine onto the dyno was a challenge because the Hedman headers hung down very close to the dyno's frame. Also, the engine had to be mounted in the front so that the headers would clear the mounting brackets. Be prepared for ground clearance issues if you decide to run a set of these headers on the street.

Fitting the strip engine onto the dyno was a challenge because the Hedman headers hung dow

Dyno Testing
After assembly, the engines were dyno tested on a Superflow 901 dynamometer. Prior to beginning the testing, calibration was checked on the dyno's torque link and fuel turbines to ensure accurate results. We started with the street version and had hoped to use a remanufactured Holley 750-cfm vacuum carb to reduce costs. However, despite making good power numbers, the engine was fussy at idle and in transition with the vacuum-secondary carb, so the 750-cfm double-pumper was installed. The four-corner idle circuit of the double-pumper made a world of difference, and the engine idled with a nice lope at 800 rpm and transitioned smoothly into the dyno pull. After making the initial tests on race gas, we filled the tank with 92-octane unleaded premium with 10 percent ethanol from the local BP station. Jetting had to be adjusted up one step and total timing adjusted down 2 degrees to 34 total for best power on the pump fuel. The power levels for this engine were just about in line with expectations at about 500 lb-ft and 500 hp.

The strip version was run on 111-octane Rockett Brand race fuel. With the single-plane intake and the big tube headers, the torque peak moved higher in the rpm band by about 1,500 rpm, and the engine peaked at 518 lb-ft and 551 hp. The addition of a roller cam and valvetrain would get this engine into the 575-600hp range, making it a very potent package.

Flow Numbers
Flow numbers from the three different head variations show the effects of the different modifications. The home port job left the standard 2.09/1.66 Cobra Jet valves in place. On the intake side, opening up the bowl and removing the pinch in the port opening improved flow at the higher lift levels. The same effort on the exhaust side resulted in no improvement, so those ports were left as is. The stock valve job limits potential improvements to the flow. The street/strip porting job gave away some flow in the lower lift ranges on the intake side, because the stock 30-degree valve seats flow better at low lifts than the 45-degree seats. However, by 0.300 lift, the bigger valves and 45-degree seats seriously outflow the stock setup. The porting job resulted in an average flow improvement of 10 percent on the intakes and 20 percent on the exhausts.

By Jay Brown

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