Stroker Kit Schooling

Increasing displacement is an easy way to extract additional power from an engine. While enlarging the cylinder bore diameter certainly increases overall size, its effects are usually limited to about 10 to 12 cubic inches during a typical rebuild. This is because excessive cylinder boring can lead to a number of concerns, ranging from compromised integrity to cooling issues, if the walls get too thin.

Adding length to the crankshaft's stroke is another popular form of increasing displacement. In a Pontiac, that typically involves resizing an original crankshaft's rod journals from the stock diameter of 2.249 inches to 2.2. Offset machining of the journal can add about 0.040-inch of stroke length, thereby providing another 6 to 8 cubic inches of displacement and taking an otherwise typical 0.060-over 455 from 468 to 474ci. The machining process does, however, require precise accuracy to ensure each rod journal's new axis is correctly positioned

Though most components within Pontiac's 326 to 455 freely interchange, the crankshaft is not one of them. Engines originally displacing up to 400ci utilized a crankshaft with 3-inch diameter main journals, while 421 to 455 engines received crankshafts with 3.25-inch journals. Because of these differences, a long-stroke 455 crankshaft will not fit a 400 block without significant modification. But the quest for additional performance associated with long-stroke engines has spawned an entire industry.

A number of crankshaft manufacturing companies and Pontiac engine builders have developed complete rotating assemblies. These affordable kits commonly inc-lude a new nodular cast iron or forged-steel crankshaft boasting longer stroke and are designed to increase overall displacement, subsequently improving performance. We've contacted several companies presently manufacturing or marketing such components, seeking professional opinions about today's "stroker" kits, and here's what they had to say.

Pontiac
Pontiac's 455 is arguably the most popular engine the division ever produced. Introduced in 1970 and available in various forms through the 1976 model year, a usable core like this is highly sought after by hobbyists for use in performance applications, and today commands a premium. Because the deck-height of any 326 to 455 Pontiac engine is the same, parts freely interchange, and several aftermarket companies offer affordable solutions to increase the displacement of any traditional Pontiac block.

Eagle specialty products
Eagle Specialty Products (ESP), in Southaven, Mississippi, has been producing Pontiac engine components for several years. According to General Manager Robert Loftis, the company's first foray into the Pontiac market was forged-steel connecting rods, which were introduced in the mid '90s. "There weren't any affordable rod options for Pontiac engines at the time, so we developed a stock-replacement H-beam, forged from 4340-steel, and it proved popular.

Recognizing the dwindling supply of affordable 455 crankshafts, Loftis states, "We crossed over into the Pontiac crankshaft market around 2000 when we teamed with Butler Performance to develop a cast replacement. At the time, original 400ci crankshafts were plentiful, so there wasn't much need for a 3.75-inch stroke unit. We found that hobbyists wanted maximum displacement, so we introduced a 4.25-inch stroke unit for the 400 block, and other products followed."

Loftis says that his company's crankshafts are cast from material with some properties of steel, making them capable of handling up to 700 horsepower. "Our stroker units are available with 3- and 3.25-inch diameter main journals, and include a 4.25-inch stroke and 2.2-inch rod journals. Our stock-replacement 455ci crankshaft contains standard dimensions-4.21-inch stroke, 3.25-inch main and 2.249-inch rod journals. They all retail for around $280."

ESP's popular forged-steel connecting rods are a two-piece design that are precision-machined on all surfaces, then shot-peened, X-rayed, stress-relieved, and heat-treated for superior strength. "Like our crankshaft, the raw pieces are produced overseas, but some of the finishing is done domestically, using state-of-the-art CNC equipment to ensure proper sizing," Loftis says. All rod sets include ARP bolts, and are weight-matched on both ends for easiest balancing. Stock-replacement Pontiac connecting rods retail for $532 per set.

ESP also offers complete rotating assembly kits for 400 and 455 engines. "Our kits include a cast-steel crank and 6.8-inch long forged connecting rods with 2.2-inch diameter journals, which otherwise retail for $466," adds Loftis. Other pieces include high-quality forged-pistons, Clevite bearings, and a host of other components such as piston pins and rings. "A basic kit starts out around $1,718, but we offer a few options, such as complete balancing using our Hines computer balancing equipment, that can add to the price."