Original Posted By: Oscar Zuniga
>From my upcoming article on the small Continentalsin Contact! Magazine:======================In order to obtain ten additional horsepower byturning the A65 at 2600 RPM rather than at 2300,Continental changed several things related to coolingand lubrication. The cap ends of the rods weredrilled with 1/16 holes to provide additional squirtlubrication for the cylinder walls, the exhaust valveswere changed to stellite-faced (a cobalt-chromium alloywith increased hardness and a high melting point), andthe undersides of the pistons were made with a wafflepattern for additional cooling. The wrist pins werealso changed to a smaller diameter, although it ispossible to create a pseudo-A75 from an A65 by simplychanging the valves and drilling the connecting rodsto allow the engine to operate at the higher RPM withoutchanging pistons, rods, or wrist pins, but engine lifeand cooling may suffer. Once again, minor changes toignition timing and carburetion differentiate thehigher-horsepower engine from its predecessor. Theexternal appearance is unchanged, and other than byexamining the engine data plate, it is not possible todistinguish one engine from the other. While many A65shave been made to operate at the higher engine speed bysimply changing propellers to obtain A75 performance,one must understand that the Continental engineers hadreasons for implementing the various changes to the engineto achieve certification at the higher horsepower, andcountless hours of operation in all sorts of aircraft andconfigurations brought to light the weaknesses that ledto the changes in later engines.====================If you have a certified engine, the conversionmust be done according to the Continental bookprocedure and the logs signed off accordingly, orotherwise you have an experimental engine.Oscar ZunigaAir Camper NX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net ________________________________________________________________________________