Tech Talk #88 – All That Glitters at the Trade Show


By David Reher, Reher-Morrison Racing Engines

“CNC is a manufacturing process, not a thought process.”

When the racing season ends, the show season begins. This winter I made the journey to Indianapolis to attend the Performance Racing Industry trade show. After several years in Orlando, the PRI Show returned to its former home in Indy, and it was amazing.

The aisles were jammed with exhibitors and buyers. Every type of motorsports was represented, from drag racing and oval tracks to road racing, tractor pulls, drifting, karts, land speed racing – in short, virtually everything with an engine and wheels.

Walking through the show inspired me to think how racing engines have changed – for better and for worse – since Buddy Morrison and I built our first small-block Chevy four decades ago in the back room at Mansfield Auto Supply.

The term “eye candy” is certainly appropriate at a trade show. I’m not talking about the attractive models on display, but about the glitter and glare of machined aluminum in nearly every booth. There was a time when we waited anxiously for the latest cylinder heads to be released by the factory – a new small-block head with angled spark plugs or a cast-iron Turbo casting with enlarged ports was a game changer. Now I can’t even count how many different competition cylinder heads are available from aftermarket manufacturers. The variations in bore centerlines, valve angles, port configurations, chamber shapes, and other features seem almost infinite.

Computer Numerical Control (CNC) has transformed the machining process, and that in turn has revolutionized racing. From contouring piston domes to carving engine blocks from solid chunks of aluminum, CNC equipment has given aftermarket manufacturers and engine builders the ability to create components on demand.

We rely on CNC machining centers at Reher-Morrison Racing Engines to make everything from header flanges and carburetor spacers to fabricated intake manifolds and fully ported cylinder heads. I wouldn’t want to go back to fitting piston domes by hand with a die grinder or machining a block manually on a Bridgeport mill. The CNC machines do these jobs faster and more accurately than I ever could. However, the advent of CNC machining is both a blessing and a curse.

CNC is a manufacturing process, not a thought process. The tools dutifully follow their programmed paths, but that doesn’t necessarily mean that the finished parts will produce optimum performance. When parts are designed by people who really understand racing engines, the results can be spectacular. However, judging by some of the pieces I saw at the PRI Show, people who lack real-world experience are just producing pretty parts – eye candy without substance.

It’s easy to be seduced by a CNC-machined part with a perfect and shiny finish, but that only means that the feed rate and the tool speed were correct when it was machined. It doesn’t mean that the piece was developed on a dyno or a flowbench, tested on a race track, and proven in competition. The familiar adage that looks can be deceiving definitely applies to engine components. Knowledgeable engine builders and successful racers understand that performance is what matters, not appearance.

Anyone remember what “GIGO” stands for in computer programming? “Garbage In, Garbage Out.” In racing terms, if a CNC head-porting program doesn’t produce the correct runner shape, the proper throat size, the optimum short-side radius, and dozens of other crucial characteristics, then it’s just making aluminum chips.

Some racers are beguiled into believing that if a part is produced with CNC, it has to be good. The important question is not how a CNC part looks, but what is the experience and technology behind its development. When we started out, we looked up to successful racers like Bill Jenkins. We tried to emulate our role models and understand how they developed winning combinations. Throughout my career, I’ve been fortunate to learn from many people and to gain knowledge from my own experiences in racing, just as engine builders in every form of motorsports build on the foundations laid down by their predecessors. So when I see a new CNC-machined part, I ask: How did this get here?

When selecting parts for a racing engine, the engineering, development, and experience that went into the components is far more important than their price. Development is expensive, and generally there is not much development involved if a part is half the price of a proven, race-winning component.

Before a racer dives into an engine project, it’s essential to have a plan. What are you trying to accomplish, what is your goal? The answers will depend on where and how you intend to race. An engine for Saturday night bracket racing has radically different requirements than a 5-second Pro Mod motor. It’s disheartening for me to see people buy stuff that they can’t really use. Too many times I’ve talked to customers who purchased a set of pistons or a pair of cylinder heads and then decided to build an engine around them. That’s the worst possible approach. Start by determining what your objective is, and then get the parts that will take you there.

Buying parts should be a process, not an impulse. It’s easy to be impulsive when you can “Buy It Now!” on the Internet, put parts in your shopping cart, and check out with a credit card number. There are many amazing pieces out there that have been developed by top-tier engine builders, refined by winning racers, and produced by savvy manufacturers. Don’t let glitter and glitz blind you to the realities of racing.