Question about crankcase ventilation

[eight-0-eight]

Hi All,

I have a spare nice, barely used, catch can setup off of a different car/engine that has all the fittings for and uses 3/8" PCV hose.
I'm going to likely run this catch can with a filter on the outlet to vent to atmosphere on my M20 when I eventually get to installing my ITB setup, however obviously the valve cover breather outlet is bigger and would need a 3/4" hose.

Before I buy a new 3/4" hose and all the fittings to get it to fit (10AN orb male to 12an flare, 120 degree 12an female to 3/4 barb, etc.), I was wondering, would there be any concerns in keeping the 3/8" hose setup and just reduce the hose from the valve cover down with an adapter to fit the 3/8". I figured since it's venting to atmosphere on the catch can side...maybe it wouldn't have adverse effects, but wanted thoughts.

Not a big deal if so, but if I could save $50+ on a couple AN fittings, that would be great 😅

Thank you!

[82eye]

have seen some set-ups that just vent to air with a small filter, so it's probably good for a try. you can always mod something fancier in after if you don't like it.

[digger]

the hoses is that big for a reason, you do not want a restriction

[eight-0-eight]

Thanks for the replies!

Yeah I figured since there shouldn't be much restriction with it being vented on the catch can side, I'd be fine with the smaller diameter hose I have but just to be safe and not add unnecesary pressure on gaskets, etc. in case there is some restriction from the catch can side, I've decided to just get the proper size hose and associated AN fittings.