Here's a bit over 375 hp from my HP289. Compression is near 10:1, s I can use pump gas. Major porting work was done on the stock HP heads with 1.94/1.60 valves. Don't have cam specs other than lift which is 0.505 in. Stayed with std. flat tappets and rockers. Considerable work done to bottom end. Pertronix ign. and 3X2 carburetion work well. The 3.73:1 gear makes it easier to leave stoplights than the original 3.50:1 gear. Engine fitted to a Cobra would work even better, considering the ligher weight. A five or six speed with a 3.73:1 or lower gear would definately allow a peakier, higher hp engine than a four speed. Just don't over-cam it.
