347 Short Block Fast Ford Formula Part 2

Makin' Power With Bolt-Ons, Boost, Or Both.

From the January, 2010 issue of Muscle Mustangs & Fast Fords

By Richard Holdener

Part 2
In Part 1 of our Fast Ford Formula, we demonstrated the effectiveness of replacing the stock 5.0L components with aftermarket bolt-ons on our 347 stroker motor supplied by Demon Engines. Equipped with factory E7TE heads, 5.0L cam and GT-40 intake, the 347 produced 307 hp at 4,700 rpm and 401 lb-ft of torque at 3,300 rpm. Once we installed the XFI stroker cam, RHS 200cc aluminum heads and Edelbrock RPM II intake, peak power jumped to 448 hp at 6,200 rpm and 420 lb-ft of torque at 5,200 rpm.

The simple bolt-ons resulted in gains of 141 hp and 19 lb-ft of torque, though the horsepower gains were as much as 200 hp past the power peak. There was only a slight drop in low-rpm power (up to 4,000 rpm), but the huge gains higher in the rev range more than offset the slight losses down low.

After swapping the blower pulley from the Novi 1220 to the Vortech, we were back in business. Loading the 347 under boost at 3,300 rpm resulted in torque figures exceeding 450 lb-ft. Running 27 degrees of total timing and an air/fuel ratio of 12.2:1, we were rewarded with peak numbers of 421 hp at 5,500 rpm and 462 lb-ft of torque at 4,200 rpm. The boost curve increased from a low of 2.4 psi at 3,300 rpm to 8 psi at 5,700 rpm. Even at 3,300 rpm, the blower improved torque production of the 347 from 401 lb-ft to 461 lb-ft.

The question was whether these bolt-on upgrades would show an even larger gain once we added boost. Our plan was to run a Paxton centrifugal supercharger on both configurations to illustrate the gains offered under boost. Given the significant increase offered in normally aspirated trim, we were anxious to see how well the Demon stroker performed with the blower.

The guys from Paxton came to the rescue with their 5.0L Mustang kit, which includes the Novi 1220 SL supercharger. The Novi featured internal oiling for self-lubrication, which meant installation of the blower kit did not require drilling and tapping (or welding) the drain pan for an oil drain back. This also meant we were not required to provide an oil-feed line. We chose the Novi 1220 for its ease of installation (and testing) and for its ideal sizing for our low-boost and power needs.

Calculations prior to testing told us the 300hp 347 might produce over 400 hp once we added 7 psi of boost from our Novi. Once we added the RHS heads, Xtreme Energy cam, and Holley Systemax II intake, the normally aspirated power output would easily exceed 400 hp, meaning the boosted motor would likely exceed 600 hp! Obviously, we needed a supercharger that was not only capable of supporting this outright power level, but one that would be equally efficient at the lower power level produced with the stock components. The Novi 1220 seemed to fit the bill nicely, as it was capable of supporting well over 750 hp, while still maintaining the efficiency at lower power levels.

To illustrate the gains offered not only by the supercharger, but by the combination of supercharger and bolt-ons, we configured the 347 test motor first with the stock heads, cam and GT-40 intake. In this configuration, the 347 produced 307 hp and 401 lb-ft of torque in normally aspirated trim. The Novi supercharger was installed and run with a 3.80-inch blower pulley and 6.75-inch crank pulley.

This drive ratio combined with the internal step ratio of 3.45:1 to produce a peak impeller speed of 36,769 rpm at a peak engine speed of 6,000 rpm (though this was well past the power peak). This impeller speed eventually produced a peak boost reading of 8 psi at 5,700 rpm (as high as we revved the stock combination). Running race fuel on the supercharged combination allowed us to get a tad more aggressive on the air/fuel ratio and timing curves than we might on the street.

Unfortunately, we were unable to fully utilize the Novi 1220 supercharger as the author made a major mistake while testing. The valve covers used for testing did not feature a baffle to eliminate oil from escaping and we were forced to attach a small shop towel over the breather vent. Though secured to the breather vent with a hose clamp, a portion of the shop towel found its way into the impeller of the Novi 1220-ouch! Luckily, we had a replacement supercharger in the form of a Vortech S-trim. Though the design (and therefore boost and power output) mirrored the Novi 1220, the downside was that it was not self-lubricating and therefore required us to provide a feed line and drill and tap the oil pan for the oil return. Let that be a lesson that hopefully you won't have to learn the hard way.