Muscle Mustangs & Fast Fords
Cylinder Head Install - Project Redheaded Step Child Part 6
Project RSC gets good heads.
No main stud girdle or Cobra crank was required for this application, and we have no reservations about adding nitrous or a Kenne Bell blower in the near future (tuning, as always, is the key). The FPS heads were installed onto the awaiting CHP short-block with a set of ARP head studs and Fel-Pro head gaskets. A huge thanks goes out to John Mihovetz of Accufab for coming to the rescue with a set of ARP head studs (ours did not arrive in time for the dyno testing), head dowels, and chain tensioner studs.
Before beginning the wild week of weirdness, we ran Project RSC's motor-which was equipped with a C&L elbow and Accufab 75mm throttle body, a set of BBK underdrive pulleys, and Comp XE262H cams-on the Super Flow chassis dyno. Also on board were a set of Hooker long-tube headers and off-road (no cats) X-pipe feeding what was left of our stainless steel after-cat exhaust. We had to hack and slash the system after installing the Maximum Motorsports suspension since the over-the-axle portion of the exhaust would not fit the new suspension. We retained the mufflers and fabricated a pair of turn downs to direct the exhaust flow under the rear axle. The motor also featured a BBK air intake and custom chip tuned by Power Train Dynamics. Equipped as described, the 4.6 put down 236 hp and over 300 lb-ft of torque at the wheels as measured on the Super Flow chassis dyno. Back-up runs showed the same numbers, so these became our new baseline before removing the motor.
With the help of Eugene Walde, Steve Abbruzzese, and Tom Habryzk from Westech, we had the 4.6 out in no time and installed on the engine dyno. The mill was configured for engine dyno use by removing the accessories (we ran only an electric water pump), installing the headers and collector extensions, and hooking up the FAST management system to our MSD coil packs. We took the liberty of running five fresh quarts of Lucas synthetic oil and a new oil filter, though the tired motor hardly deserved the high-quality synthetic lubrication for just a few dyno runs. Equipped with the stock non-PI intake and Accufab/C&L throttle body combo, the pathetic project powerplant pumped out an uninspiring 264 hp and 326 lb-ft of torque.
The difference between the chassis dyno numbers and those generated on the engine dyno was just under 12 percent, well under the 20 percent numbers often quoted by some engine builders, chassis dyno operators, and others. Skewing the power differences by removing the accessories, mufflers, and air intake only served to reinforce this point. There is no straight percentage difference between chassis and engine dyno numbers that can be applied to all circumstances.
Having illustrated the reality between engine and chassis dyno numbers, we removed the tired motor and proceeded to swap over the necessary components required to bring the new CHP/FPS powerplant to life. Given the 235 hp generated at the wheels on the chassis dyno, we were roughly 65 hp away from our goal of 300 hp. We were hoping the new short-block and ported heads would take us at least most of the way there.
Our expectations of the new configuration were further increased by the fact that a compression test of the original 4.6 revealed one extremely weak cylinder. Off the original motor came the oil pump, pan, and pickup, along with the cam sprockets, chains, and tensionsers. Also part of the swap were the XE262 cams, stock lifters, and valve covers. Additional carryover items included the intake and throttle body, the front cover, and, naturally, the headers and dyno exhaust.
After a 20-minute break-in period, the new CHP/FPS 4.6 was run in anger and tuned to produce 308 hp and 347 lb-ft of torque. This new combination represented a jump in power of 44 hp and 21 lb-ft of torque over the original long-block, through the power difference was as great as 68 hp at 6,000 rpm. Given the minor gains achieved thus far with the project, we were excited to finally see some big numbers appear on the screen. Though we still had not improved the power output enough to reach our goal of 300 hp, we had taken a serious bite out of the required power gain.