popierre and I have had several ideas regarding Precision Eagle 4.2 engines from Bryon. I was able to make significant improvement by:

- using higher octane fuel
- using synthetic oil at 100:1 mix ratio
- switching to ProZinger series props
- finding a build error in the carb

However, the last, big change was provided by popierre - he suggested dumping the PurrPower muffler and replacing it with a Pitts style from JA Engineering.

What a difference - gained 300-400 RPM, and the engine operating temp has dropped dramatically. After running with the PurrPower, I could fry an egg on the crankcase. Now, I can touch the JA Pitts muffler immediately after running, without pain, and the crankcase and head temps can be described as 'warm to the touch.'

I'm now running 6.2K -6.3K with the ProZinger 24x10. This is spec in the Bryon materials for a Zinger 24x10 - I don't know how they could have gotten there running natural oil, low octane and a PurrPower muffler.

This plane will fly, this year, finally.

Thank you, to all those that contributed, especially, popierre.

The PurrPower muffler does create a nice sound, but its better used as just an engine mount - cut the header off to make room for a JA Engineering Pitts muffler, you'll be glad you did.

DaleCS