By David Reher, Reher-Morrison Racing Engines
“Building better engines was literally a matter of national survival.”
As a professional engine builder and a self-confessed motorhead, the development of internal combustion engines is both my livelihood and my passion. While unlocking a few more horsepower in a racing engine is always rewarding, I recognize that ultimately it’s not a matter of life and death. There was a time, however, when the fate of the world literally depended on engine development.
In the early days of World War II, only a few hundred Hurricane and Spitfire fighter planes stood between Hitler’s Messerschmitts and the conquest of Great Britain. The Rolls-Royce Merlin V-12 engines that won the Battle of Britain in 1940 prevented England’s fall and secured a toehold for the eventual liberation of Europe. In the later stages of the war, the armadas of heavy bombers powered by mammoth Pratt & Whitney radial engines turned the tide of war in Europe and the Pacific in favor of the allies. These were some of most powerful and most reliable piston engines ever built.
Ancient history? Hardly. Sixty-five years ago, engine designers grappled with the same problems that confront racers today as we strive to improve performance. The chief difference is that the resources of entire nations were focused on the war effort; building better engines was literally a matter of national survival.
Today a top-tier racing team might have a dozen people working on engine development, but during the war years, the industrial might of the U.S., Great Britain, Germany, Japan and Russia was focused on accelerating piston engine technology. Hundreds of thousands of engines were designed, manufactured, tested and flown under impossible deadlines and relentless pressure. Ford built motors, Oldsmobile made cannons, and GM turned out tanks by the thousands. If you think that getting ready for the U.S. Nationals is a big deal, just imagine the logistics of preparing for the Normandy Invasion on D-Day.
I’m a frequent visitor at a shop in Breckenridge, Texas, that restores and preserves historic warbirds. Every time I see these remarkable machines, the skill of the people who created them awes me. They weren’t geniuses and master machinists – they were simply ordinary people doing extraordinary work in an exceptional time.
Among them we can thank Pratt & Whitney engineers for the development of tri-metal crankshaft bearings. Babbit bearings could not withstand the loads produced by 2,500-horsepower engines, so Pratt & Whitney developed the bearing alloys that we now take for granted. Connecting rods were a weak link in these engines; desperate to keep the planes flying, an investigation into metal alloys produced connecting rods made from 4340 alloy steel. Sound familiar? Today forged 4340 steel connecting rods and crankshafts are standard equipment in many of our Super Series engines.
Valvetrain dynamics was also a concern back in the day of the big radial engines. Although engine speeds were relatively slow by today’s racing standards, the immense forces caused the cylinders to flex and the valvetrain to become unstable. The engineers quickly had to understand the fundamentals of camshaft profiles. They lightened the exhaust valves by making their stems hollow and filling them with sodium. That seemed like a good idea until the improved heat transfer produced coking in the valve guides. When the exhaust valves began to tulip under the intense heat of combustion, they devised dome-shaped valve heads. Cast cylinder heads soon gave way to stronger forged aluminum components as power levels escalated. Many drag racing engines have followed this same path.
The accepted engine development program was to test until failure. I’ve seen photographs of rows of dynamometers that stretched as far as a football field. Engines were run at full power until something broke. The carnage was then inspected and a cure quickly devised. Then the motors were run again until the next failure. Not surprisingly, problems shifted from one area to another as the next weak link in the chain was revealed. People worked as though lives depended on their success – because they did.
One of the Allies’ strategic advantages was high-octane fuel. While the Nazi fighters were flying on 87-octane gasoline, the Allies enjoyed the performance advantage of American-supplied 100-octane fuel, which allowed faster climbing rates. By the end of the war, aircraft fuel had reached a performance number of 150 as the pilots had to intercept German V-1 rockets that were raining down on English cities.
Superchargers, turbochargers, water/methanol injection to forestall detonation, and nitrous oxide injection to boost horsepower were developed to increase the performance of piston aircraft engines. Double and triple stage superchargers were introduced, with planetary gears that shifted to increase rotor speed at high altitudes – think of a Lenco transmission mounted to a blower. The Luftwaffe discovered that injecting nitrous oxide into the intake charge could dramatically increase horsepower in high-speed dogfights, but at the cost of decreased engine life. Decades later, racers still strive to find the best balance between power, reliability and cost.
It was a time of ingenious solutions. When General Electric engineers wanted to test turbochargers at high altitude, they mounted an experimental engine in the back of a truck and ran it at the summit of Pikes Peak. When manufacturing intricate turbine blades seemed an insoluble task, an engineer realized that using the same lost wax process used to make dentures would also work for turbocharger components. It wasn’t just man’s work to build high-performance aircraft: Miss Beatrice Shilling invented a device that allowed carburetors to function properly under negative g loads. Thousands of similar small steps determined the final outcome of the war.
Today we enjoy the advantages of time- and labor-saving technology. A Merlin V-12 crankshaft, for example, began as a 500-pound chrome moly steel forging; when it was finished, it weighed 120 pounds. Every ounce had to be machined away by hand on manually operated lathes and mills – CNC machining centers simply didn’t exist. Metallurgy also has made great strides, and today we have valve springs and piston rings that were unimaginable in 1940.
The arrival of jet engines at the conclusion of the war meant that piston engine development for military aircraft stopped virtually overnight. Ironically, racers are now the prime movers in making piston engines more powerful, more efficient, and more reliable.