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Pro Stock Engine Technology

500 cid, 8 rods and pistons, 16-valves and pushrods – That's where the similarity ends...

By Len Emanuelson

Page 1 of 3

For a gearhead it’s always interesting to look at the upper echelons of motorsports to see what’s ticking under the hood. F1, Sprint Cup, and endurance cars are all fairly engaging from an engine perspective, but nothing tops drag racing for its sheer power, variety and ingenuity. In a single event you have vehicles competing from 8,000 hp Top Fuelers to 300 hp Stock Eliminator cars.

But the most intense class for any serious engine builder is NHRA Pro Stock. With these naturally aspirated 500 cid engines spinning 10,500 rpm and producing upwards of 1,450 hp and 800 ft.lbs. of torque, you have to ask yourself – how’s that possible?

Getting that much power out of a two-valve, normally aspirated 500 cid V8, has taken years of development – five horsepower at a time. Who does that? The answer is a very small circle of engine builders and parts suppliers who devote their lives to building the quickest and fastest normally aspirated door-slammer engines. It’s a tight-knit community of 100 people or less dedicated to extracting every last horsepower out of a production OE-based 500 cid engine.

This level of performance and dedication doesn’t come cheap. In fact, you can “rent” one of these engines (and many teams do), for $50,000 per race or $1.2M per season. The way the rental program works is that you show up for a race and the engine builder delivers the engine to your pit. The engine builder handles all required maintenance at the racetrack (valve spring replacement, tuning, etc.). After the race, the engine builder picks up the engine and takes it back to his shop. While $1.2M may sound like an astronomical amount of money (the parts and labor cost to build one cost about $100,000), the technology required to field a competitive motor is priceless.

We spoke to some of the most notable racers, engine builders and parts suppliers to get an idea of what goes into a Pro Stock engine. Kurt Johnson out the famous Warren Johnson Racing stable, Roy Johnson, dad and engine builder for Allen Johnson Racing, Joe Squires from Bryant Racing, Nick Ferri of the newly formed Jeg’s engine shop (JNR Racing), Scooter Brothers from Comp Cams and Dan Jesel of Jesel Valvetrain Innovation. This all-star lineup gave us a good idea of what goes into a current NHRA Pro Stock engine.

The current NHRA Pro Stock record holders are Rodger Brogdon with a 6.495 ET and Erica Enders who holds the MPH end of the record at 213.57mph.

Many of the front-runners produce enough power to win. The Pro Stock winner on any given day is the racer who can apply that power to the ground in the most effective manner. Tuning the clutch and chassis to make a smooth, hooked-up run from start to finish is the challenge. Taking advantage of the 8,500-10,500 rpm powerband is key to a successful run.

So let’s get down to the nuts and bolts. All three marques – GM, Dodge and Ford – start with a factory-sourced Pro Stock engine block. Of the current engines, GM has been around the longest with the DRCE2 and DRCE3 both still in use. The Dodge folks have the Hemi 99 and the Hemi 06, and Ford’s latest engine is called the 2009 Pro Stock. Most of these blocks are made out of compacted graphite iron (CGI) that resist bore distortion and crankshaft deflection. It’s safe to say that all three 4.900˝ bore-spacing blocks are very similar, having been homogenized by the rules, and virtually everyone we spoke with claimed that no single design had a clear advantage over the other. Several people thought that the Hemi was a little stronger at high rpm, but right now nobody is complaining. That was somewhat of a surprise that a race sanctioning body had finally achieved parity between the dueling manufacturers.

The most important thing to mention about these Pro Stock blocks is the cam placement. The higher, the better – in fact one of the significant changes between the DRCE2 and DRCE3 blocks is that the cam has been moved up in the DRCE3 more than a full inch. With a typical stroke of 3.500˝-3.600˝ and the fact that virtually everyone uses steel rods, why is a high cam position so important? It all comes down to valvetrain rigidity.

After spending countless hours on Spintrons and back and forth to the dyno, valvetrain manufacturers and engine builders discovered that the stiffer a camshaft was, the more power the engine made. Not so difficult to understand when you consider the 1,000-pound open valve spring pressures and their effect on camshaft torsional rigidity and cam timing. So not only is the cam positioned higher, the diameters of these steel billet cams have grown to 60-70 mm and even 80 mm in some cases. Another aspect of higher cam placement is that the pushrod is shortened making it stiffer and the valvetrain more rigid.