Thank you for your response. The cylinders are just back from Millinium Ent for nicasil. Brand new shiny and I have bead blasted the RC valves (4) to clean the carbon off. I am suspicious that some of the nicasil plating has changed the clearence within the RC valve recessed area in the top of the exhaust port... I can't feel any bumps or irregularities (as you sometimes do after re-plating) in the recess area but, it clearly has some sort of problem. I agree that putting it together would jepordise the servo and pgmIII. I suppose I am going to have to come across a right-angle grinder with a sanding roll and create some clearece in the RC valve recessed area...