Check valve info needed

[_Twisted_]

I want to put a check valve inline for the fresh air to the motor, the chevy originally had them on the air tubes for emissions but the threaded side is metric.

The ones that come come in the kit for evac setups, can any one give me the specs on the NPT sizes? I want to put a nipple on it.

[1meandemon]

the tread is 1/2 npt.

[_Twisted_]

thanks