Displacement Games
Finding Cubic Inches Between the Lines
By the fall of 1983, Maurice Petty had become convinced that some of the engines outrunning Petty Enterprises were carrying more cubic inches than NASCAR’s rulebook allowed.
There were respectable ways to respond. Complain to NASCAR. Build a better legal engine. Stand around the garage grumbling about what everybody else was getting away with.
Maurice chose the traditional racer’s solution.
He built a bigger engine.
358 Meant 358
NASCAR’s displacement limit was 358 cubic inches. Not 360 because the machinist got enthusiastic. Not 365 because nobody was looking. Three hundred fifty-eight.
Maurice built Richard Petty an engine that measured nearly 382.
Twenty-four extra cubic inches does not wander into an engine because somebody leaned a little too hard on the cylinder hone. This one had crossed the line, driven another block and found a parking space.
Building the horsepower was the easy part. Maurice Petty knew how to build an engine.
The interesting problem was getting nearly 382 cubic inches past an inspection intended to find anything larger than 358.
NASCAR Had a Way to Measure It
NASCAR did not have to tear an engine apart every time it wanted to check displacement. Officials could use an air-volume test through the cylinders, pumping a known amount of air into the engine and measuring how much volume was available.
That works nicely when the engine seals the way the measuring equipment expects.
Maurice arranged for this one not to.
He used wax in the cylinder-head area to hold the valves slightly open during the test. With air leaking past the valves, NASCAR’s equipment was not getting an honest measurement of the cylinders underneath.
The engine could stand in the inspection line carrying almost 382 cubic inches while the test saw something considerably more respectable.
Then somebody started it.
Wax Has One Unfortunate Characteristic
Engines make heat, and wax has a predictable response to heat.
Once the race got underway, the wax melted away. The valves returned to doing what valves are supposed to do, and Richard Petty suddenly had access to all the cubic inches Maurice had actually installed.
Before the race, the engine behaved one way for NASCAR’s measuring equipment. Once it got hot, it behaved another way for Richard.
That is not working at the favorable end of a machining tolerance.
That is sending an engine through inspection wearing a false moustache.
The Plan Worked Beautifully
At Charlotte on October 9, 1983, Richard started twentieth in the Miller High Life 500. Then he drove through the field and won.
It was career victory number 198.
That created the one problem Maurice’s wax could not solve.
Winners get inspected.
This Time NASCAR Wanted the Engine Apart
The No. 43 went to post-race inspection, where officials were no longer interested in repeating the convenient little air-volume test from before the race.
This time they were going inside.
By then the wax had already done its job and disappeared. Unfortunately for Petty Enterprises, that also meant there was nothing left to help nearly 382 cubic inches continue pretending to be 358.
NASCAR measured the engine at 381.983 cubic inches.
There are inspection arguments where everybody spends twenty minutes staring at a micrometer and debating a few thousandths.
This was not one of them.
NASCAR wanted 358.
Maurice had brought almost 382.
Maurice Didn’t Blame the Tape Measure
Petty Enterprises was fined $35,000 and lost 104 championship points, although Richard was allowed to keep the victory.
Maurice did not waste much time suggesting that twenty-four additional cubic inches had somehow assembled themselves while nobody was watching. He admitted the oversized engine was his doing and maintained that Richard had not known what was inside it.
His later explanation made a certain amount of racing sense. If Richard had known the engine was illegal, Maurice said, he probably would have finished a strong second rather than win the race and hand NASCAR the car everybody would want to tear apart.
That is an unusual defense.
It is also probably the only one where finishing second is offered as evidence of innocence.
The Inspection Trick Was Temporary
The clever part of Maurice Petty’s engine was not simply making it oversized. Any competent engine builder with the right parts could make an engine larger.
Maurice figured out how NASCAR intended to measure displacement and then arranged for the engine to give the inspectors one answer before the race and Richard Petty another after the green flag.
The deception lasted exactly as long as the wax did.
Then Richard won, NASCAR opened the engine, and 381.983 cubic inches had nowhere left to hide.
Maurice got his bigger engine.
Richard got win number 198.
NASCAR got the last measurement.