Muscle Mustangs & Fast FordsHow To Engine
Demon 347 Short-Block Cylinder Assembly - Fast Ford Formula Part 1
Makin' Power With Bolt-ons, Boost, Or Both
The stroker fuelie motor was configured on the engine dyno with an MSD billet distributor, Meziere electric water pump, and 1 3/4-inch Hooker Super Comp headers. Knowing boost was in the cards for Part 2, we installed a set of 36-lb/hr injectors in our factory 5.0L fuel rails. These will eventually limit the power output of our supercharged combinations, but they were all we had at test time.
Prior to making power pulls, the motor was treated to a computer-controlled break-in procedure using conventional Lucas Oil. While the break-in procedure wasn't necessary for the factory hydraulic roller cam, achieving proper ring seal is every bit as important. Rushing things such as the break-in procedure is a surefire route to reduced engine life. The FAST XFI engine management system was hooked up, and after dialing in the air/fuel and timing curves, the normally aspirated 347 produced 307 hp at 4,700 rpm and 401 lb-ft of torque at 3,300 rpm. Though the factory heads, cam, and GT-40 intake limited peak power production, torque production from the Demon stroker exceeded 350 lb-ft out to 4,600. Had we tested the motor lower in the rev range, torque production was over 400 lb-ft at 3,300 rpm and would likely have exceeded 350 as low as 2,500 rpm. Not exceptional power, but the stock components were limiting what was otherwise a stout short-block.
The first of three to go was the stock 5.0L cam. Though a hydraulic roller, it offered little in terms of performance. Sure, the idle quality was good and the fuel economy was decent, but it was holding back our 347 stroker motor. It was replaced with a stroker-specific XFI grind from Comp Cams. The dual-pattern XFI236HR-14 cam combined 0.579 lift with a 236/246 duration split (measured at 0.050) and a 114-degree lobe separation angle.
Naturally, the cam required a decent set of cylinder heads to take advantage of all that lift, so we installed a set of aluminum heads from RHS. A legendary name in the cylinder-head business, RHS offers a number of both cast-iron and aluminum heads for 5.0L Ford applications. It even has new CNC-ported versions we hope to test on a future build, but this 347 received a set of assembled, as-cast 200cc aluminum heads designed as a direct bolt-on for hydraulic roller cam applications.