I've got a 2-bbl manifold, and in the side of the base that the carb goes on, there was a threaded hole that was capped off. Our machinist had no idea what it was for, so my dad put a nipple and then we hooked it up to the PCV (seemed to make sense from diagrams etc). My 4-bbl manifold does not have this, and I am not certain if it is in another spot or if it's even 100% required. Thanks for any help.

Typically the PCV goes to the base of the carb itself.

Most manifolds have a port near the back in the number 8 (or 7) cylinder runner. Used for power breaks and usually automatic tranny.

What don't you think is 100% required? The hole in the manifold or the use of a PCV valve? A port in the manifold is only required when you need one. Carbs have ports, too, so depending on your vacuum accesory needs, you might not need a a port in the maifold. If you mean the PCV valve, it's not required but it does a good job at keeping your oil clean. I'd recomend you use it.

Tim.

I meant I wasn't sure if that hole in the manifold was needed. There is a little T fitting at the back of the manifold that I use, but also this one had one in the side too so I was curious. Maybe it was drilled/tapped from previous owner, who knows.