New Petcock

Does it need some sort of sealer on it before being screwed into the radiator? If so, what? Thank you.

Just put a new one on my 51 Cambridge. No sealant needed.

Pipe thread? Always a teflon pipe tape or paste.

If it doesn't have to be restoration-accurate, I like the ones with a little hose bib extension.
If you add a short length of hose to the bib, the coolant drains past the lower radiator support.

I recently had 3 of those from different sources in which the 'wing" used for tightening and loosening just spun. the last one was front NAPA at $12.00, more than twice the price of the other 2. BTW, They appeared identical,

Ran into the same thing from my NAPA part as well, had to use a punch in the hole to peen the crimp down tighter.

Hello again. Okay, I've have 1 member who said no sealant needed and 2 members who say use some sort of a sealant. Anyone else care to comment? Thanks..

Yes on sealant for pip threads, I prefer the paste.
As for the faulty petcocks, I haven't had that problem, but they're a lot cheaper than $12 at my local hardware store.

Brass on brass pipe thread low pressure; threads would distort enough to seal a low pressure system. Put any type sealant on it & you won't have to tighten that much to prevent even seepage.

The ones I've bought usually already had some sort of sealant on it.

The last time I needed one was a few years ago and every one I tried had the problem with the wing that spun before it was tight. I ended up buying a compressor drain valve that looked the same but made better for about the same price. No problems since.

I'm going to s*it on both sides of the fence; I've done it both ways in many situations. Brass on brass and about any other type including a steel motorcycle tank, the brass (or, in the case of aluminum, the Al threads) will deform just enough to seal if I was too cheap to buy tape or dope. With the addition of sealant, its like very inexpensive assurance.

This is a NOS petcock going into a original factory 69 radiator. Maybe I should ask how did the factory do it back then. I do have both pipe dope and teflon tape in my toolbox, so no big deal. I just like keeping things as original as possible. Many thanks.

Only if you anticipate having to remove it in the future. In that case pipe dope or teflon would be cheap/easy insurance IMO.

on both
Yes sealant. Loctite blue works excellent and you can wipe off the excess.

On the drains, Exactly what I did, bought 10 or them, made by Milton in this country But they don't have the little extension om the end for a hose, BUMMER!
The parts store ones cost me about 3 hours or more of utter frustration

Doubt the factory had the worker applying tape or sealant on every valve they installed. Factory would have ordered valves with a sealant already applied to threads, if they used any at all. Typical of any production/assembly factory workings.