I installed a CHT gauge on my project car and ran wiring, but didn't bother to install the sender ring under the #3 spark plug before installing the engine .. basically because I didn't want to remove the induction system and tin, etc. on an engine that I'd not planned to keep for very long. But lately, I've been thinking it'll be longer on this engine than I'd originally planned - and having the CHT hooked up would be nice.

I've run the wiring into the engine compartment (not sure but I think most run it under the tin, no?). So anyway - can I just bend the 14mm sender ring so that the wire come up vertically thru the tin (under the spark plug boot), and slip the ring on before installing the #3 plug? Or is that not gonna work?

You are over thinking it.
Jut pull the washer off the spark plug and put the ring on the new plug and put it in the hole.

You can put a finger in through the hole in the tins for the stock CHT and put a finger on the new CHT wire to hold it in place. Once it takes a set it will stay in place in the future.

The tough part is that you need to ground a groove in the boss of the spark hole to make room for the CHT sender wire.

Zach

Yep. Just make sure it's on flush and your plug is fully seated. If it's not fully seated it will read cool, by quite a bit.

This is part of why I asked.. because I'd seen people cut a groove in the head so that the 14mm ring set flat where the electrical wire connects.

Now, your comment is throwing me a little tbh - you say just replace the spark plug washer [ok, great!] - but then you're talking about cutting this groove too ???? I don't suspect that can't be done with the tins on, right? Sorry, but you confused me more.

I took off the washer, bent the CHT sender so the wire had a natural 90 degree exit back out the plug hole and it works just fine - even after another recent plug change. No issues.

Thanks for confirmation on this, I'm gonna try and keep it simple..

Cutting the head just makes plug removal easy. With out the cut you must be careful when playing with that plug, but it does work fine.