To all knowledgeable BCP,

Looking for first hand intel on performance mods for the Conti 0-300, such as new cylinders with higher compression pistions, intake porting, exhaust improvments etc. What are the rewards, the risks and the straight skinny on the idea.

Thank you in advance,

Mapleflt

Good luck! I’ve asked this here before. The consensus is there’s lots of guys running high compression pistons up north. There’s no approval for this but parts can be found and I’ve not heard any horror stories as a result. The other legal improvements amount to fine wire plugs, k&n style air filter, and re-pitching your prop. If you’re talking about a 170 application, you can run a seaplane prop. My straigh tail 172 is not approved for the seaplane prop so I just had my 76” re-pitched for max rpm. I have not heard of anyone porting and polishing the cylinders on these engines so I cant offer much in that world. Fly it light, thats the only viable performance gain that I’ve come up with.

Mapleflt. Are you in or heading toward owner maintenance category?

I owned a 170 for years and this was discussed many times.
Cheap and easy trick is to use C-85 pistons in an O-200 or O-300,
don't know how much it bumps the compression but it does something.
Might have to bump the timing or maybe even use electronic ignition to take advantage of it.
You might also lose the utility of running 87 octane car gas though.
I think you do have to slightly modify the pistons though.
Harry Fenton's webpage would be the place to find out about that--
a good site with lots of misc info on the four-banger Continentals which may also be applicable to the O-300.

http://www.bowersflybaby.com/tech/fenton.html

Lightspeed Engineering's main thing is electronic ignition systems,
but they also sell high compression pistons ( 9.4:1 ) meant for the O-200.

http://lightspeed-aero.com/Services/O200Pistons.htm

I'm very seriously considering an OM certificate, what are the pros and cons ? In all honesty while a 180/185 would be amazing to have for what I do the 170 work fine but I'd like to get the motor back to its "rated " power not looking to make it a hot rod !!

Mapleflt wrote:I'm very seriously considering an OM certificate, what are the pros and cons ? In all honesty while a 180/185 would be amazing to have for what I do the 170 work fine but I'd like to get the motor back to its "rated " power not looking to make it a hot rod !!

Biggest downside is resale value will take a hit. You can only sell in Canada. If you want to sell it in the US, everything has to be overhauled first. Also, you aren't legal to fly in the US.
If neither of those is a concern, then I'd say do it for sure.

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So you have a tired O-300? An overhaul will bring it back to rated power. Even if you went to the OM category, I would be inclined to stay with the standard compression ratio. Bradford, ON? Where do you buy most of your fuel? Having the option to burn boat gas is pretty attractive if you're on straight floats.

Had a cliped wing taylorcraft, put c-85 pistons in and 4 equal legnth pipes on it. Made a big difference. The pistons need a 45 degree chamfer to clear the sides of the combustion chamber but the compression ratio is about 8.5 so boat gas should still be ok. And its a simple change back if you want it back in standard category. Also had to drill the main jet up 2 drill sizes as it was lean. Im sure it would really help takeoff and climb

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Lots of great intel, my thanks to the BCP community.

Mapleflt