There is no such thing as a Polution control valve or PCV tap on any model aircraft four stroke engine.

The majority of model four stroke engines do have a crankcase vent and most have a nipple to plumb the vent outside a cowling venting to atmosphere. This vent is not plumbed to the fuel tank or muffler! Agine do not plumb this crankcase vent to the fuel tank or muffler.

YS engines are an exception here as they never have vented crankcases and case pressure is used for different purposes with that engine.

If your engine used a pressure tap on the stock muffler then do plumb a pressure tap line to the tank breather from the new muffler. If your stock muffler did not employ a muffer tap the it may not be needed at all.

No matter who or how they got there if your new muffler has two taps or holes you can bet they were intended for !. fuel tank pressure tap 2. smoke oil injection port.

If you don't have smoke then plug the extra hole. If you want to use a muffler pressure to tank pressure then pick one and use it. Usually the best pressure is obtained where the tank first opens up in area. However on those box mufflers thats always a crap shoot but not a big deal.


John