Tee dee .049/.051 crankcase pressure

I personally could never get this to work and that was with a check valve. Once you drill the case your committed. If any air leaks are present, the system will fail. In my opinion the instructions tell you to drill a far too big of a hole. The engine would surge violently up and down. Backplate pressure is far superior. The stock needle valve also makes setting the engine on pressure troublesome. Even with the backplate tap, the hole required for this to work properly isn't greater than the width of a pin. I was using brass pressure nipples tapped into the aluminum. I would then take a extremely fine piece of wire and place the wire into a candle to blacken it. I would solder the hole I drilled in the nipple and insert the wire. Solder won't stick to the blackened carbon on the wire. Once removed it left a very tiny hole in the nipple. The other problem you may experience is case flooding. You can't turn the engine over without it priming the venturi and this can be problematic until you find a sequence to start it. These are findings I experience so good luck. Ken