The 170 needs to use a PCV valve that has a smaller bore than the valve used on 198 and larger engines. It's been N/A for years. Even the larger-bore metal-type PCV valve has been N/A for quite some time. You can buy new ones (eBay, Year One, etc.) for more $$ than they should cost.
The late-style all-plastic valves work perfectly in a '66-up valve cover, acceptably OK in the up-to-'65 valve cover. If you're shopping at NAPA, get an Echlin 2-9325 valve and a Balkamp 6301051 or 6301073 grommet.
The way you make this valve work with your '64 valve cover: Remove the metal valve and its locknut. Save the 2-legged spring from the underside of the PCV valve "cap" that fits on the valve cover. Make a sandwich in this order: PCV valve (push the non-hose end through the cap from outside to inside), spring retainer, grommet (push onto non-hose end of PCV valve from the bottom). Sometimes the spring retainer won't fit over the plastic valve and you have to leave it off. Push this "sandwich" onto the valve cover chimney. It won't look original, but it'll fit and work fine.
The old metal valves can be cleaned and re-used for years, but after awhile they just plain wear out. The spring gets tired, the plunger gets worn, and then they cause poor idling.