f16man

I HAVE BEEN READING THAT ALMOST EVERYONE IS LOOKING FOR MORE SPEED OUT OF THEIR BOATS BUT I HAVENT SEEN MUCH ON THE ENGINES THEMSELVES. I HAVE BEEN AN AUTOMOTIVE MACHINEIST FOR 33 YEARS AND HAVE DONE A LOT OF HIGH PERF WORK ON STOCK ENGINES INCLUDING DUCTED FAN ENGINES IN THE 70S AND 80S. MOST WERE OS 77, ROSSI 81 AND CONVERTED A OS 90 MARINE TO DUCTED FAN USE, BUT ALL ENGINES HAVE ONE THING IN COMMON...... GETTING THE AIR-FUEL MIXTURE IN AND GETTING THE BURNED CHARGE OUT. MANY OF YOU MAY BE TIMID ABOUT THE INTERNALS OF AN ENGINE BUT IT IS NOT ROCKET SCIENCE. EVERY RC ENGINE I HAVE TAKEN APART HAS HAD ISSUES IN PORTWORK AND CRANKCASE AREAS. ALL THE MACHINED PORTS HAVE SHARP STEPS LEFT FROM THE MACHINE PROCESS, THESE NEED TO BE SMOOTHED AND CONTURED TO FLOW WITH EASE. THE BASIC PORT DESINES ARE GREAT BUT IT IS TO EXPENSIVE FOR THE FACTORY TO FINISH OFF THE PORT WORK BY HAND.ALSO COMPRESSION AND PIPE LENGTH PLAY A HUGE ROLL IN PRODUCING A SCREEMING ENGINE THAT WE ALL MUST HAVE!!! AFTER RUN IN OF THE ENGINE THE COMPRESSION CAN BE RAISED TO RUN MORE NITRO IN FUEL AND THEREFORE MORE POWER. SOME ENGINES HAVE HEAD SHIMS THAT CAN BE REMOVED TO UP THE COMPRESSION . ANOTHER WAY IS TO SHAVE CYLINDER HEAD OR TOP OF SLEEVE, DONT GO CRAZY REMOVING TO MUCH MATERIAL HERE , THE SEALING FACES OF THE SLEEVE AND CYLINDER HEAD NEED TO BE IN CONTACT WITH EACH OTHER AND HAVE A SMOOTH FINISH TO SEAL. AFTER DOING THIS STUFF TO YOUR ENGINE YOU WILL GET MORE RPM'S AND MORE POWER, NORMALY YOUR PIPE LENGTH NEEDS TO BE ADJUSTED, NORMALY 1/4" TO 1/2" LONGER THIS YOU HAVE TO PLAY WITH. SO AFTER YOU HAVE MODDED YOUR HULL AND GOT THE BOAT TRIMED OUT AND STILL WANT MORE SPEED ,WE NEED MORE POWER , MORE PROP AND MORE RPM. I AM SURE THAT THERE ARE SOME PORT WORK GURUS OUT THERE THAT CAN ADD MUCH TO THIS AND WOULD LOVE TO SEE LOTS OF INPUT.

jetpack

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There's a good motor section here at RCU that many people have contributed to concerning hop ups. Lots of the car guys are really into hop ups also, and have started a few good topics...i've swiped ideas from them also.

I like to dismantle and work on motors also for my boats. Usually its because I've bought them used, some with very little run time, and just never put away properly.

I'll do the same as you and do careful stock removal to help airflow, but been finding the patternmaking of all the newer motors is quite good, and theres usually only small steps that need taking care of but its satisfying to know at least its been looked at.

Your right about the sleeve fit, some of mine by the time I've removed the sleeve and cleaned the case and sleeve for assembly, it will have lost some of its fit. If that is the case, when the block is warmed up to put new bearings in, i'll slip in the sleeve at the same time and use a rolling paper cut to size and layed onto the exhaust side surface. It forms just enough of a gasket to seal it well, but not enough to distort anything.

I always upgrade to stainless steel bearings, and some I will be trying ceramic bearings in the front where vibration occurs due to flywheel balance - hopefully to time and match the wear that the rear bearing sees.