Ross -we did not have the colder plugs in when the trouble started. I had colder plugs in during the all my ground testing though. They are going back in.
Stephen and Pierre -normal flying logic is why I am putting new pistons in. There was more of a worry about overspeeding it than anything. This was the wrong thinking. YThe engine an handle well over 6,000 rpmsThis is a car engine in an airplane. Why can't you run at 29"? 29" is 6000 rpms on this engine. With a 1.72 gear box that means that prop is at almost 3500 rpms. 23 inches is 2700 rpms and is 305hp. To go to 29" and get full power you would have to change the gear box. But I think 305hp is more than enough power. So you don't take off at full throttle, you take off at 23" and 2700 on the prop. As you climb you can continue to push the throttle in but you do not want to go above 23". You can in theory maintain 305 hp all the way up 6000 or 7000 ft DA. Generally accepted airplane engine management goes out the window here unless you want to put new pistons in all the time. Overspeeding this engine is much better than overboosting it.
I'm just a wee bit confused here (and truly not trying to be sarcastic) but RPM and MP aren't a direct link (ie mutually exclusive) in any installation of any engine with any gearing when a CS prop is being used....MP can/should vary depending on the load applied at the prop, so I too am scratching my head here just a little bit. Perhaps Ross can put this in easy terms for me. With a CS prop, RPM should be controlled by the load on the prop, not MP - no matter whether it's an auto engine or subiewankendiesel or lyco or what. With a FP prop, then yes, MP will affect RPM.
Is your prop not twisting up enough? Regardless of gearing and regardless of what you need to take off, you should be able to push at least standard atmospheric pressure through it like any other auto installation or any installation for that matter....the gearbox isn't necessarily the controlling factor if indeed the prop is CS. If the prop is FP, then I can understand a bit more of what you're saying. If the prop is either FP or acting that way, then it's not the gearbox you change, it's the prop pitch.
Anyway, I'm not trying to open a debate, nor trying to be negative. Just trying to understand what you're saying here because it just doesn't make sense to me at this point. Perhaps it will with some further explanation.
Keep plugging away. I'm truly interested in your progress and just trying to understand things in your installation as I know several other people going the V8 route would like to know as well.
Ross, you've been through a lot of this and know an awful lot about this, can you educate me here a bit?
Cheers,
Stein