Airworx 180HP O-300 STC

[ghostflyer]

I have written in the past about modifying the continental engine O-300 and have now come to the conclusion is that it’s safer and more reliable to leave it factory standard. However we did find some of the castings very crude. The intake plenum chamber was polished out including the cylinders intake and exhaust ports. I think it was No.5 piston /cylinder always seem to run rich in comparison to the other cylinders , this issue went away after polishing. I now wish in the beginning we had just put a bigger and more powerful engine in and not wasted our money.
In my humble opinion and a little what i know Continental tried to develop this engine but decided in 1964 to develop a clean sheet IO-360 engine . which produces between 180-220 hp .

[akahrs757]

Was this in relation to the airworx work? Or was it a normal overhaul?

[ghostflyer]

This is where I had the bright idea of extracting more power out of a O-300. This was done nearly 20 years ago. I was friendly with a tech rep from Continental and having many discussions with him and some of his colleagues . I thought a change was a good idea. My engine needed a top overhaul at that time and it seemed a good opportunity to “improve” it. The castings were shocking and very rough. No 5 cylinder was very rich all the time and the casting condition in the plenum chamber was shocking . We acquired new pistons /rings , and cam shalf and cam followers. The intake and exhaust ports were polished and slightly modified in shape. The first hours on the dyno ,the oil temp was very cold but when fitted to the aircraft it was very hard to control ,it over temperature all the time . To cut a long story short ,I would never try to modify a O-300 engine . The amount of money and time spent ,not worth it. Plus I had to put my aircraft in a temporary cat of experimental. In its present design ,the O-300 is a bullet proof and reliable engine . It’s my belief that continental , RR and Rutan tried to modify the O-300 design concept and failed. There was a LuLO-300 engine
[water cooled] and that had cooling issues. If you want more power and grunt get another type engine . eg Bird dog — similar to the 170 but totally different engine .

[abushey123]

To the previous question on reliability of increased horse power o300. I have run a o300d with cylinder port and polish, sump port and polish, an adapter to run a ma4spa carb to allow a bit more airflow, 10:1, and advanced timing for almost 1000 hours. The only things to note is harder starting due to higher compression and using a carbon propeller, higher CHT (425f) on long hard pulls and a slight increase in oil burn. The largest gain I noticed was from using the original o300d cam and NOT the superior or new Continental cam as the profile does not allow rpm to pass 2700. The current setup allows for 2825 on takeoff using a 86” sterna. With a stock wing, 31” bushwheels on a standard day 29.92 and 15 deg at sea level to about 2000 feet I could constantly climb around 1500-1600fpm at 70 mph. This was shown on both an VSI and GPS. Empty weight of 1270 and takeoff weight of 1700ish lbs. The compressions were great all the way to removal of the engine and I never had any abnormal metal in the screen during changes. Engine had 1700 hours at the time of removal.