Pietenpol-List: squirt holes
Posted: Sat Apr 24, 2004 6:14 pm
Original Posted By: "Les Schubert"
Les,The squirt holes were originally used exclusively on the A-75 and A-80 toprovide cooling oil to the waffle pattern cast into the underside of thepiston dome. The squirt holes eventually became standard and replacementrods from Continental in the later years all had them. It is better to havethem than not. Also, the A-75 pistons, as said earlier, have the waffle onthe underside but are otherwise identical to SOME of the A-65 pistons. Ifyou have these pistons in the A-65, as many engines do, then that is goodtoo.If these to internal mods are present, then it is merely necessary to dofour more things to get 75 hp: rejet the carb, replace the venturi with alarger one, reset the magneto timing, and install a propeller that can dothe following: it is rated at 75 hp (it won't be overstressed), it can bespun at 2650 rpm (it won't be overstressed), and it will turn the minimumstatic rpm for the engine prop combination which should be about 2400 rpm orso. It is imperitive that the prop be sized to allow for 2650 rpm when youare at wide open throttle at sea level on a standard day. If you don't turnup the rpms, you will not develop the power. Many have done all the modsexcept change the prop and are disappointed becuase the 65 hp prop will notallow the rpms to be developed. To turn up the higher rpms, the prop mustbe either less in diameter (discouraged) or less pitch (encouraged). Withthe piet design and its slow speed, always try for the biggest diameterpossible for the best efficiency. 74 to 76 inches is not unreasonable.Chris Bobka----- Original Message -----
Les,The squirt holes were originally used exclusively on the A-75 and A-80 toprovide cooling oil to the waffle pattern cast into the underside of thepiston dome. The squirt holes eventually became standard and replacementrods from Continental in the later years all had them. It is better to havethem than not. Also, the A-75 pistons, as said earlier, have the waffle onthe underside but are otherwise identical to SOME of the A-65 pistons. Ifyou have these pistons in the A-65, as many engines do, then that is goodtoo.If these to internal mods are present, then it is merely necessary to dofour more things to get 75 hp: rejet the carb, replace the venturi with alarger one, reset the magneto timing, and install a propeller that can dothe following: it is rated at 75 hp (it won't be overstressed), it can bespun at 2650 rpm (it won't be overstressed), and it will turn the minimumstatic rpm for the engine prop combination which should be about 2400 rpm orso. It is imperitive that the prop be sized to allow for 2650 rpm when youare at wide open throttle at sea level on a standard day. If you don't turnup the rpms, you will not develop the power. Many have done all the modsexcept change the prop and are disappointed becuase the 65 hp prop will notallow the rpms to be developed. To turn up the higher rpms, the prop mustbe either less in diameter (discouraged) or less pitch (encouraged). Withthe piet design and its slow speed, always try for the biggest diameterpossible for the best efficiency. 74 to 76 inches is not unreasonable.Chris Bobka----- Original Message -----