Randy lifted the engine cowling in the back, and they set to work. Woody could follow most of what the two were doing easily enough. They checked the distributor, coil, points, spark-plug gaps, and timing. All were in tiptop shape. Tappets, tiny as toys, were checked also and proved to be correctly adjusted. Then Worm did something that Woody had never seen before. He went to his own tool kit, which he always kept locked, and brought it over. He opened it up, and inside lay his tools, each contained in a velvet covering and glittering like the operating instruments of a surgeon. He took out the two top trays and laid them carefully on a cloth on the workbench. From the bottom of the toolbox he extracted a stethoscope such as doctors use for chest examinations. Woody nearly laughed. Worm with the stethoscope around his neck, dressed in his soiled coveralls, looked like a caricature of a mad doctor. "Fire her oop," said Worm. "She's no breathing right." Randy turned on the ignition and pressed the starter button, and the Black Tiger purred contentedly to herself. "Rev her oop tae five thousand," said Worm. The Black Tiger snarled in anger and impatience as Randy pressed the accelerator down. Worm put the stethoscope to his ears and the listening apparatus to the carburetor intake pipe. How he could hear anything above the deep roar of the engine Woody could not understand. But Worm was listening as intently as any doctor to the chest of a tuberculous patient. He raised a long finger in the air, and Randy depressed the accelerator further. The Black Tiger's roar was now such that it seemed it must bring down the building. Worm nodded and took off the stethoscope as the roar of the engine died to a quiet purr again. "It's as I thought," he said. "She's no breathing right around five thousand eight hundred. The air's no ramming through as it should. It's a delicate matter, and I hae me doots whether we can fix it." "Have to change the contour of the intake and exhaust ports, huh?" asked Randy. "Aye," said Worm. He saw the mystified look on Woody's face and explained. "It's a matter of using air pulsations tae shoot air through the intake port and suck it oot of the exhaust. I've not got the time tae explain it further. Ye'd find it in Davie if ye ever looked. But it's controlled by the size and contour o' the intake and exhaust ports. It's like using the air as a supercharger for itself." Woody now began to understand what Worm had meant when he talked about the difference between butchery and surgery in servicing automobiles. "I'm thinking," Worm said to Randy, "that if the intake ports were polished a bit it might do the trick." Worm bent over to look. "Somebody installed the wrong gaskets," he said, straightening up. "Yon gaskets are too thick. A sixteenth of an inch will make a difference."