<div id="post_message_987782">Hi, I'm running a Zenoah G62 in my dragster.I can't get it to run smooth.Since this is a airplane engine I thought you knowledgeable guys here will have the answers.I'm running 87 octane for fuel and a 40:1 ratio.That's what I run in my gas cars.The high speed needle is about 1 1/4 turns out.She idles fine.When i pull the triggerthe rpms goup but itseems rough not asmooth transition.Is it the octane? How high a octane and what fuel /oil ratio should I run. If that's the problem.I have since switched to 91 octane and 32:1 ratio.I did rebuild the carb and replaced the spacer between the carb and head.Any info will be appreciated. Thank you. (Oh just a foot note ,I ran the car in May on my street and being useto the smaller Zenoahs with a fan and shroud .I ran the dragster up and down the street forgetting this engine does not have the fan or shroud on it.I'm thinking it overheated. It never ran the same after that.)I removed the head today and everything looks fine inside.No scoring ,no signs of overheating on the parts.The onlything I found was the gasket between the head and the carb spacer was breaking down.It was new when I put the new spacer on.There was a little fuel on top of the spacer.Also when I removed the head the head gasket it was wet on the case side.Maybe the surfaces are uneven.I also run a straight header pipe.Could the lack of back pressure be a problem.Thanks.</div>