The wrist pin is, arguably, the most highly-stressed part in a racing engine. The expansion of burning gases in the combustion chambers applies tremendous force on the piston tops. That force is transferred to the connecting rod via the wrist pin, a short-length of thick-walled, tubular steel. Inside an 850 horsepower, NASCAR Sprint Cup engine running at 9000-9500 rpm, a crushing force of six tons hammers each wrist pin about 77 times each second. This punishing, cyclical load lasts up to 600 miles in some races. Wrist pins in a Cup motor are subjected to unbelievably high levels of both bending and radial stress which they must sustain for a considerable period of time.

The BME Wrist Pin, introduced in 2000, grew out of Bill Miller’s three-step business strategy: 1) make the parts racers need, 2) sell them at a fair price and 3) engage in a ruthless pursuit of quality. Bill Miller’s idea: manufacture a wrist pin which could both meet the difficult durability challenge of Sprint Cup racing and be a better value.

A BME Wrist Pin begins with 9310 vacuum-arc-remelt (VAR) steel, a raw material with the purity and strength necessary for wrist pins used in Sprint Cup and other gasoline-burning race engines but, also, a material which is more cost-effective than some of the exotic steels used by other wrist pin manufacturers for those applications. A VAR steel is melted twice. Conventional foundry processing produces an ingot of 9310 steel. This ingot is placed in a water-cooled, copper crucible. The crucible is sealed, a vacuum is applied, then a high-amperage, DC current is connected to an electrode inside the crucible. Arcing between that electrode and the ingot remelts the steel. The vacuum prevents contamination resulting from molten steel reacting with the atmosphere and any gas bubbles released during remelting are drawn off by that vacuum. The result is an ingot with outstanding internal structure and excellent chemical homogeneity. The foundry then processes ingots of 9310 VAR into round, bar stock.

The strength and durability of a BME Wrist Pin comes just as much from the processes used to manufacture it as it does from its raw material. A section of Bill Miller Engineering’s Carson City, Nevada factory is equipped with CNC turning centers devoted solely to Wrist Pin production. The CNC’s cut 9310 VAR bar stock into sections, the inside and outside diameters are precisely machined and the ends are cut and ground. 

After rough and final machining in the CNC’s, BME applies a unique, mirror finish to the inside and outside surfaces of each Pin using special lapping machines. Only half a dozen manufacturers in North America have such equipment and because of that, BME Wrist Pins for Sprint Cup engines have a mirror finish which is an unusual, high-quality feature.

BME, also, manufacturers a line of Wrist Pins for alcohol-burning and nitromethane-burning, supercharged drag race engines. Remember that force on the piston top we talked about earlier? In an 8000-hp, supercharged, nitro-burning engine in a Top Fuel Dragster or a Funny Car, that force is even more extreme, perhaps as much 50 tons.

There are very few raw materials with the incredible strength required by wrist pins in a blown-fuel, drag race motor. BME Pins for nitro-burning, supercharged engines are made of VascoMax C-300, an exotic, very expensive, nickel-cobalt-titanium steel “superalloy” with very high ultimate tensile strength (294,000 psi) and an extreme fatigue endurance limit (one billion cycles at 125,000 psi). Like Bill Miller Engineering’s 9310 VAR Pins, the VascoMax C-300 Wrist Pins receive BME’s special manufacturing processing which gives the O.D.s and I.Ds that distinctive, high-quality, mirror finish.

With the Bill Miller Engineering Wrist Pin, once again, it’s clear that BME’s ruthless pursuit of quality pays off with a product that is reliable, durable and performs beyond the expectations of the many stock car and drag racers who win with them..