RE: McCoy 19 redhead
That's a lot of prop for those old engines. But being as it is running that fast, I would continue to use the same prop.
Hard for me to remember the props now for the 19.
I do remember running a 10 X 6 on the McCoy red head 35
A 9 X 6 on the My McCoy 29 all silver Super Stunt 29,
I don't remember on the 19's but 9 X 4 comes to mind.
On the K&B and Fox 15's I ran a 8 X 4
They would only run up close to 10,000 but the fuel was generally 5% nitro and 20% castor oil.
Need to run a lot of oil in these for they have a bushing crank and a iron piston running in a steel sleeve.
I was going to say castor oil but you guys don't seem to use it in Europe.
I do remember the McCoy's didn't last long unless you ran them just on the 2 cycle edge of the break into 4 cycle. If you peaked them out - they were worn out after just a few runs.