Your nearest auto parts store carries many adapters, T's, Y's, etc. It should be easy to locate a 3/16-to-3/8 brass or plastic adapter.
Don't drill/tap your manifold; besides being irreversible, it's a lot of work and it's also likely to get metal filings into your motor.
Last edited by miraclepieco; 08/05/2016 3:47 AM.
