Mind you, Gurney wanted his engine to run just fine on pump gas, and he wanted it to last a long time, so killer compression ratios and otherworldly rpm from the race track were out. At a moderate 4,200 feet-per-minute piston speed, this twin (with a bore and stroke of 5.00 in. x 2.8 in.) will peak at 280 hp at 9,000 rpm. To make power despite these limits, the engine has to breathe at state-of-the-art level, and to that end Gurney’s long-time associate, ex-dirt-tracker Chuck Palmgren and others have developed highly optimized and rational porting. Each cylinder’s four valves are set at very low included angle to give a flat, open, and fast-burning combustion chamber.