Mike, I picked up a beautiful 45vac, I have several including a twin, and this one came with a turbo button. Of all the dozens of motors I have in boats right now from .12s to .90s I have no other engine with a turbo head. I stock lots of plugs but no turbos. Instead of contacting Chris to try tighter clearance in a .21 with a brass button, this would serve two purposes and also let me see what I can wring out of the motor in a rigger. I need some hands on experience to feel the difference in squeezing the clearance with adjusted timing and props. I can always just find a standard button but this interests me. I have several 45 riggers ready to run including a Stingr from Armen Boldy in Great Britain with a new style OPS 45 I feel is the one for the November race here. Keep an eye out if you don't mind. Thanks