Ken: My Alon has an engine mounted spin-on filter. When I tried to look up the brand of adaptor, my logs only gave a part number. I suspect that it may be a Continental part. When I installed a filter on my former Skylane I found the Continental adaptor to be the lowest priced and, of course, it fit just right and gave no trouble.
The manifold pressure gauge and tach jointly determine power output. With a variable pitch prop, a given reading on these gauges will indicate the same power as a lower RPM and higher pressure, or conversely a higher RPM and lower pressure. With the fixed-pitch prop on our Alons, the tach alone serves to read power output because the manufold pressure is determined by the density altitude, RPM, and the pitch twisted into the aluminum blank of the prop. Another way of explaining this is: ** If you installed a super climb prop on your Alon and could get the 2475 RPM red-line on take-off with full throttle, you would also read the local barometric pressure reading on the manifold pressure gauge (if you had one). After you levelled off from your spectacular climb, you would have to throttle way back to keep the prop from exceeding red-line and the manifold pressure would be very low. The prop would be taking such a small bite for each revolution that you couldn't get much power out of it and the plane would be real slow, like running a car in first gear on the freeway. ** Install a cruise prop and the RPM will read very low on takeoff (maybe 2150RPM) and once again the manifold pressure gauge would read local pressure. Your takeoff acceleration and climb would suffer (like starting your car from a stop in third gear), but with just the right prop pitch, you could level off at cruise, and with full throttle, just get red-line RPM and all the manifold pressure available at the altitude you levelled off (and a lot of speed too). So, given the prop you have on your plane and the tables from your Continental Engine manual, you can find percentage power for a given RPM. And, don't throw out the tach; you need to stay below red-line. Any competent auto speedometer shop can re-calibate a mechanical tach, and it's inexpensive. Alternatively, you can just get your I/A to use his calibrator during your next annual and you will know exactly what the error is. Regards, David N6359V Alon A-35
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