JDM Engineering Stroker Kit Install - Stroker Ace - Tech

The rotating assembly is dropped into an aluminum Three-Valve 4.6 block that is common to the new S197 cars. According to D'Amore, there is no special machining of the block to accommodate the increased stroke of the crank. Also, JDM has the bottom end of each stroker put together exclusively by Anthony DiSomma of M2 Race Systems. While the clearance specs for the engine are proprietary, D'Amore made sure to mention how extra attention is paid to that part of the build throughout the assembly, with the Three-Valve modular engines being especially reliant on proper oil control. "The reason why oil pressure and control are so important on these motors is because the cam phasers in the Three-Valves rely heavily on oil pressure, especially at idle," he says. "Having too much clearance is bad for the cam phasers."

While the stroker crank is the main bit of attraction for this engine, with the extra cubic inches, a good set of cylinder heads need to be bolted on to get more air to flow into the cylinders. The heads are stock Three-Valve heads, though they've been massaged by DiSomma for maximum flow. "The heads get a full CNC port job, as well as a valve job," D'Amore says. "The heads are then equipped with 1mm oversized valves, heavy-duty valvesprings, and titanium retainers."

Another note of interest was D'Amore's usage of the stock camshafts. While a set of aftermarket cams will unquestionably make more power over the stock cams at certain points on the dyno graph, D'Amore likes using the stock cams because they allow him to tune the torque curve of the engine easier. "The reason we use the stock camshafts is because they allow me to tune how I want in terms of the retard to the cams themselves," D'Amore says. "I do this with the cams to broaden the torque band, and the stock cams make doing it so much easier. So far, we've been able to get a new Mustang GT into the 11s with the stock cams and a stock torque converter in an automatic [naturally aspirated-Ed.]. This is great for everyday driveability. You can make as much power as you want, but if the car isn't driveable, then it's useless to customers. As we progress, we'll be testing cams and looking to produce 400 hp at the wheels on motor and much more with a blower or turbo."

So how much power is the JDM naturally aspirated stroker engine worth? Let's look at one of the in-house cars at JDM. This particular '07 S197 started out as a stock GT with bolt-on parts such as an exhaust, cold-air kit, underdrive pulleys, and a custom tune making 306 rwhp (see dyno graph). After putting in a 298-inch naturally aspirated stroker motor with the identical aforementioned bolt-on modifications, the same car pounded out 352 rwhp. In addition, the torque numbers at the rear wheel increased from 323 to 362.