G.M. yanked away Mid-American’s largest line of business, a valve lifter guide, a part used deep inside an engine block, that provided 80 percent of its revenues.

For this purpose, an “exhaust valve lifter” is usually fitted, by means of which the exhaust can be kept permanently open, in order to relieve the resistance to pedalling which the compression stroke would otherwise offer.

Cole starts Stanway's pickup, advises him that a bad valve lifter is his problem and suggests that an oil additive will probably get him over the 1,200 miles to Savanna.

Clickety-click: it's in the valve or valve lifter.