Frank H. Cicerale
January 1, 2008
Here is our stroker ace completed. We cruised to JDM Engineering to get the 4-1-1 from the crew on the new Three-Valve stroker engines, and they allowed us to help assemble one. Talk about crazy!

When it comes to making power, the old saying that there's no replacement for displacement has been replaced, in a sense, with the sick, power-producing properties of a turbocharger, centrifugal, or positive-displacement supercharger. Even a small hit of the sauce can bring about an on-demand supply of extra ponies. So are extra cubes really necessary?

While the dollar-per-horsepower number of a blower, turbo, or laughing gas may outweigh the cost of building a thundering naturally aspirated combination, there's still the allure of a modular engine sporting a larger-than-normal cubic-inch figure. In a sense, while power adders are good, utilizing them in conjunction with a supersized stroker motor is even better.

Building a stroker motor is nothing new in terms of the venerable 5.0 pushrod motors, but for the modular crowd, especially those with the newer Three-Valve 4.6 engine, strokers are becoming an accepted and easy way to make more power. With the bore spacing for the 4.6 block being extraordinarily close when compared to the spacing in the 5.0 pushrod engines, the easiest way to add inches without compromising the block's cylinder sleeve structure is to drop in a longer-stroke crank.

The goods themselves can be seen here. The rotating assembly is all forged components for the utmost in strength and reliability.

One of the leading performance shops pumping out stroker Three-Valve mod mills is JDM Engineering in Freehold, New Jersey. JDM and company spearhead Jim D'Amore have long been associated with muscular Mustangs and fast Fords, and they were kind enough to allow us to tag along as they built a brand-new Three-Valve stroker engine.

The main focus of the stroker engine is, obviously, the components to the rotating assembly, specifically the crank. JDM uses a forged-steel stroker crank, forged Manley H-beam 4340 connecting rods, and a set of forged Manley pistons, all of which were manufactured to JDM specifications. The 3.750-inch stroke of the crank, when combined with the standard 3.555 bore of the 4.6's cylinders, brings the cubic-inch displacement to 298-17 ci more than the factory offering of 281. D'Amore points out, though, that while the cubic-inch increase may be small in number, it's more profound when looking at it in terms of engine percentage increase.

The interesting thing is why JDM went with a crank that creates 298 cubes as opposed to the more common 302 offering. "I wanted to be able to turn higher rpm in this motor, so I went with the 3.750-inch crank to gain the right rod angle," D'Amore says. "With this crank, there should be no problems with the engine both on the track and on the street for an extended period of time. With the longer crank, there would be an increase of side load on the piston skirts, which would lead to a shorter lifespan for the engine."

In addition, JDM currently offers two versions of its Three-Valve stroker package. One is made specifically for naturally aspirated combinations, while the other is geared exclusively for super-charged applications. "The major differences between the naturally aspirated and supercharged stroker engines lies in the pistons, the compres-sion ratio, and the ring gaps," D'Amore says. "In the naturally aspirated motors, we use a flat-top piston and run a 10.8:1 compression ratio. The supercharged motors are obviously different because you don't want to run into any detona-tion. For those motors, we put in a set of dished pistons, lower the compression ratio to 9.8:1, and run a tighter end gap on the piston rings."