By David Reher, Reher-Morrison Racing Engines
There is a rule of thumb in the computer industry that speed and memory double every six months – at half the price. Alongside today’s Pentium processors and mega-gigabyte hard drives, the personal computers and that were state-of-the-art a few years ago now seem like steam-powered antiques.
The PC revolution has had a huge impact on drag racing – and not just in data acquisition systems and weather correction programs. The development of powerful mini-computers has dramatically cut the cost of horsepower by making sophisticated CNC (Computer Numeric Control) machining readily available. The result: Racers get more bang for their bucks than ever before.
A CNC machine doesn’t get tired, doesn’t take coffee breaks, and doesn’t ask for vacation time. When it is programmed properly (which is a science in itself), a CNC machining center will work nonstop until the job is finished.
Cylinder heads are the most important components in a racing engine. Consider the heads that are now available to sportsman racers: For approximately $7,000 you can buy a pair of CNC-ported Dart Big Chief heads that offer nearly as much airflow as the hand-ported Pro Stock heads that carried a $40,000 price tag just a few years ago. The cost per cfm has fallen nearly as dramatically as the price of personal computers.
The development of reasonably priced CNC machining centers has made it practical for Reher-Morrison Racing Engines and other engine builders to become “manufacturers” – a status that was once was reserved for a major company with a mountain of capital. Today there is a thriving cottage industry that turns out everything from billet water pumps to specialized tools on these marvelous machines.
Porting a cylinder head by hand is a time-consuming and tedious process. It requires experience, patience, and skill to produce a complex three-dimensional shape like a runner. By dramatically reducing the time and human labor required to port a head, CNC machining has allowed engine shops to produce high quality components at very reasonable prices. Just as SuperFlow put flow benches within the reach of every shop and serious racer, CNC machining centers have given engine builders the capability to produce heads that offer exceptional performance.
CNC machining can accurately duplicate a port design again and again. Instead of spending weeks with a hand grinder trying to produce eight identical runners, a head porter can concentrate on making one perfect port. The contours can then be digitized and “cloned” with amazing accuracy. Naturally the final blending and critical valve seat areas must be finessed by hand, but CNC machining can do most of the tedious, dirty work.
As a result, it’s never been easier or less expensive to go fast. A few years ago, a typical sportsman dragster used a 468-cubic-inch big-block with cast-iron cylinder heads. Now with the growing popularity of fast brackets, Quick 16 shows, and Top Sportsman-type competition, the power requirements have escalated. Today our most popular Super Series engine is a 555-cubic-inch big-block, and I foresee the day when engines with more than 600 cubic inches of displacement and Pro Stock-style spread-port heads will be standard equipment in the fast sportsman divisions.
With the cost of airflow falling almost daily, it is more important than ever to match the cylinder heads to the engine. I shudder when I see a big-inch motor that’s saddled with inadequate cylinder heads. Installing heads with ports that are too small for the short block is like a putting a restrictor plate on an engine. It’s the worst of both worlds: an expensive motor that is neither responsive nor powerful.
It is more expensive to fix or upgrade a poor combination of components than it is to buy the right parts the first time. It’s like buying a new car without the options you really want; it would cost a bundle to add air conditioning or power steering after the car leaves the assembly line. If you are going to invest in a large displacement engine, please spend the money to put good heads on it. Don’t leave 150 or more horsepower on the table; after all, isn’t power the reason you wanted a big-inch engine in the first place?
When Reher-Morrison Racing Engines first started to develop spread-port heads for our Super Series sportsman big-blocks, a typical 18-degree Big Chief intake port flowed 470 cfm. It wasn’t too long before they were up to 500 cfm; now our latest 14-degree Pro-style heads will move 530 cfm. It takes virtually the same amount of time to CNC machine a port that flows 530 cfm as it does to machine a 470 cfm runner, so the cost-per-cfm is actually less with a good head design.
Twenty years ago, a set of titanium valves was a rather expensive proposition. Today the price of titanium is about the same as it was in 1975 – which means that a set of lightweight valves is now a relative bargain. When you remember how much the prices of cars, groceries, and postage stamps have inflated in the last 25 years, then titanium is no longer a luxury. Titanium valves can totally transform the characteristics of a racing engine by extending its operating range and improving reliability.
It’s not just cylinder heads that have benefited from the computer revolution. Thanks to CNC machining, racing pistons are lighter and have more accurately machined ring grooves, pin bores, and skirts. The piston manufacturers have CNC-machined dies that shape the piston forgings to near-net shape, thereby minimizing weight. Not too long ago, it was a big deal to have a piston dome profiled to match a particular combustion chamber; now many sources offer that service.
Just as racers compete for victories and bragging rights, engine builders compete with each other to produce better products. We want to produce as much reliable power as possible at a fair price. Silicon chips and personal computers have become as valuable in this effort as the wrenches and ratchets in our toolboxes.