Hello Dick,

First off, thanks for the reply. Very informative. I ran tuned exhaust on pattern ships in the early 80's, but these gas engines have me baffled when it comes to this subject.

Yes, I was incomplete in the info provided, my fault there. It is hard to get a solid answer with out the proper info.

As for prop choice, I was using both an AirModels 28x12 and a Mejzlic 28x12. Both are 3 blade props. I see that plently of guys are using 28.5x12 Mejzlic 3 blade props. I really would like to run a 2 blade to help in the 3D envelope but would consider the well suited 3 blade. I like how quite these types of setup are and so do the neighbors. I did not have a way of checking the rpm's but the engine prop combo pulls the 40%Carden 330 weighing in at 41 lbs with no effort. I had gone with the suggestions of Brian Huffmier at DA on header lengths and several others thought it was about right for me. I knew that adjusting them may be necessary, but just don't want to botch a set of headers until I can understand more.

The engines throttle responce all starts out well on the lower end, it is that when I get up to say mid range, I am moving the stick quite a bit with no noticable rpm change and them BAM, it is on the top end. Like I said, I have played some with the curve, but no help. IThis weekend, I switched back to stock mufflers and the throttle responce is exactly and perfectly like I like it. Every throttle click advance, I can notice a rpm change and quick throttle advances are taken with no hesitations. This is why I am having a time understanding these can setups. I do run my engines just a bit on the rich sideon the low end, meaning that after a start the engine and taxi out to take off position, it takes just a bit to clean the engine out and I don't have any problems after the first 10 - 20 feet of take off roll. The high end is set close to where it needs to be cause I am not hurting on vertical power. It will pull vertical for as long as I want with no loss of power noticed on cans or stock mufflers. Upon landings, I find my engine temps to be between 160-170 degrees. I have never had any issues with my engine setups on stock mufflers with this way of thinking on engine tuning for me.

I will have to look into your advive on this problem. I did not expect this to be easy as the pattern planes weren't, but I am just trying to make sure that my understanding is there before I botch anything up.

Thanks for the advice and info.