more rpm's from reed valve engine

I have several reed valve engines .049 cox. I am running 10% nitro fuel and the engines are getting about 11,500 RPM's with a 6-3, 2 bladed prop. I get about 12,600 from some McCoy Wen Mac engines set up the same way. Is there any easy way to get 13,500 to 14,500 out of these engines? I need more power for a quick lift off.
THANKS BILL

sport and stunt flyer

Use a 5x3 prop.

Want more power, Add NITRO!

Them Cox suckers like 25% or more. They will burp around on 10%, but they are a lot happier with more.

Do you have the double port engines? You can use the piston/cylinder from a TD, a high compression head, and, as mentioned, more nitro or a smaller prop. You can also open the venturi area a bit for better breathing and some play with the reed valves.

However, after all is said and done, just remember the old addage: "You can't make a silk purse out of a..." you get the idea. A reed valve Cox engine is always going to be a reed valve Cox engine and a go-kart engine won't push an Indy racer very fast around the track.

Someone with a more retentive memory should find the posting on how to fit / tune these. Wish I had saved it !

Here it is!

http://www.clstunt.com/cgi-bin/dcforum/dcboard.cgi?az=read_count&om=2789&forum=DCForumID1