I've been running Norvel big mig for several years on different combat planes. Threw a rod on one right through the engine housing. Sig replaced even though I admitted using MCP and flying in combat. I put new OS needles on mine. You have to shorten the barrel about 1/8 inch, but the needle seems more friendly than the stock Norvel needle. Same carb though. There is no air bleed screw--just a small hole. Make sure it's clean. Rick Fraley once told me that I could bore it out with a numbered drill if I needed mored air (leaner), but once drilled, there is no going back. I resisted and I now have one of the Norvels on a delta wing thingy called a Wild Wiz that just screams. Good idle and transistion. I am using a bladder tank. I have had excellent results with regular old Wild Cat fuel (10%) and Tower plugs. The guys above are correct that these engines improve with age. My biggest complaint is the tendency for these engines to flood and lock up. I try and keep fuel line pinched off, but still have to blow out excess fuel when starting. Cost me a number of launch on time points.

(I tried to include a couple of photos. Don't know if they came through.)

Greg