Muscle Mustangs & Fast Fords
Ford Stock-Block Stroker Engine Swap Part 2
Dyno Testing Our Home-Built EFI 331 Stroker Is Only The First Stage For This Affordable Small-Block.
In taking advantage of everything the engine dynamometer has to offer, one can extract horsepower and torque numbers, as well as exhaust gas temperatures, air and fuel consumption figures, water and oil flow, in and out water temperatures, and more. Plus, the engine dyno make it much easier to swap out major engine parts for testing, such as cams, heads, and headers.
The more high-strung your powerplant, the more you need an engine dyno to dial in the tuneup. Formula 1 teams even use engine dynos that can simulate the engine loads from a specific racetrack on a turn-by-turn or lap-by-lap basis. With this level of information, F1 teams can tailor engine specifications to each track, and also (attempt to) ensure reliability over a race season.
In this engine test, we're not going to such an extreme, but we wanted to break in the engine on the Horsepower by Hedrick dynamometer, and then tune it for optimal power and torque. We'll follow this test next month with more dyno testing on a different induction system, and finally the aforementioned chassis dyno test so we can determine the exact loss through the drivetrain.
As you are able to extract more data from an engine dyno, it is a bit more laborious when it comes to bolting the powerplant up to the dyno. We spent several hours sorting out throttle actuation, header clearance, and other assorted issues.
We intended to use a stock A9L Ford EEC-IV computer to run the EFI system, and so we could do that on the engine dyno, we ordered one of Ford Racing Performance Parts' new M-12071-A50 electronic fuel-injection harnesses. It's designed with the crate motor guy in mind, who wants to run the factory electronics in his hotrod but doesn't want to modify an old, crusty harness. It has provisions for an electric fan, tachometer lead, fuel pump power, air conditioning switch, and more. The harness comes with great instructions on how to get your engine up and running in no time flat, and if you have a Fox-body or SN-95 Mustang, it will easily replace your factory harness as most of the harness extensions are designed with those chassis in mind.
Tuning the EEC-IV box was handled by Tony Gonyon of HP Performance in Orange Park, Florida. Gonyon uses SCT software to write the program and burn it to one of SCT's computer chips. In addition to the tuning software, Gonyon also employs a SnEEC EEC-IV datalogger from Race Systems. It's a piece of hardware that is no longer produced, but it allows for optimal tuning of EEC-IV-controlled engines.
After entering the engine specifications into the dyno software, we cranked up the stroked small-block Ford and Mark Hedrick performed a break-in regiment, which loads and unloads the engine and alters the engine rpm. Having the dynamometer do this rather than having a human manually operate the dyno makes the process much more accurate and less tedious for the dyno operator. With the break-in complete, Hedrick made a few low-rpm, full-throttle pulls to creep up on the max rpm he had set at 5,500.
With the air/fuel ratio looking good, the oil temperature reading a steady 150 degrees, and the water temp at 140, our first 5,500-rpm pull netted 390.4 hp and 378.1 lb-ft of torque. This came with 29 degrees of total timing. For the next pull, we raised engine rpm to 6,000; peak power went to 398.3 and peak torque arrived at 378.3. Average power and torque was up thanks to a better air/fuel ratio. For the third pull, fuel was trimmed between 4,000 and 4,700 rpm, and ignition timing was increased to 31 degrees total. Peak power came in at 396.7 and the torque logged at a peak of 377.3 lb-ft.
We were thinking the tuneup was dialed in, so we made another pull to back the third run up. But this time at 5,600 rpm, power and torque dropped off by some 70 hp and 70 lb-ft! After a quick inspection, we tried again but the engine coughed at 3,800 rpm and we aborted the pull.