TR2/3/3A TR3 Brass Heater Valve to Head - How to treat threads, if at all?

Today was big day - the TR3 started today for the first time! So now the sorting begins...but it looks like, assuming all works out from here on in, I may be driving the car this summer, instead of just thinking about it.

Step #1 is stop the leak. It's the the brass heater valve to the block. When I put it in (eons ago) I am pretty sure I used a very light amount of teflon thread. When the car got up to temperature today, it started leaking around the base of the valve where it attaches to the head. So, I took it apart, I think I see a few remnants of teflon in one or two threads, but I sure didn't use much. Should I have threaded it in dry? It was certainly tight so that wasn't the issue. Any other magic goop to use? Couldn't find any other posts on the topic, thanks in advance,

Just ordinary pipe thread. Nothing special in my mind. Teflon tape should do it. Nice and tight though and make sure the threads in the head are clean. Tom

I also used Teflon tape - quite a few wraps of it.

The thing is, you need to stop tightening when it is pointed in the correct direction, so you can't just tighten the bejeezus out of it. The Teflon may help keep it from leaking.

I agree, a single turn of teflon tape should do (although my preference is to use paste instead of tape and of course two or three turns instead of one wouldn't hurt anything). Also check the threads on the valve, it may have gotten dropped or something and damaged a thread.

Thanks guys, my sense is too little tape and too much tightening. Threads look good, Ill give it another shot. I guess it just didn't look like a coarse "pipe thread" in the traditional sense to me.

The brass valve is the main part, but the horizontal outlet tube is screwed into the side of the brass valve and these threads can also leak. Check if yours is leaking only down at the block - or from the upper threaded part.

I have experience the head being full of rusted hardened scale and the brass valve only felt tight. Take a look down into the head with a flashlight.