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O.S. 61 sx-h cylinder head replacement

Old 07-29-2010, 06:06 PM
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Default O.S. 61 sx-h cylinder head replacement

I have an old 61 sx-h wc that I ran in a helicopter years ago and was wondering if there was a way to replace the cylinder head for airplane applications. Will the 61fx head fit on the crankcase? Will there be issues with performance. I have read where the 32 sx and 32 sxh were the same engine, so you could just replace the head.
Old 07-30-2010, 09:13 AM
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Default RE: O.S. 61 sx-h cylinder head replacement

Well, the timing of the O.S. Max .61 SX-H was different from the .61 FX, which was the contemporary. We don't know if the .61 FX cylinder head will fit the .61 SZ-H case. They are discontinued, so we don't have any parts to do a trial fitting. A heli engine will work in an airplane if you are careful to restrict airflow over the heatsink head to keep it from running over cool. Many times, just cutting it down can help.

One main consideration is that heli engines are designed to run much higher RPM than airplane engines. A .61 heli engine will run in excess of 15,000 RPM at full throttle, while an airplane engine will turn about 12,000-13,000 at full throttle when propped correctly to suit an airplane.

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