Do you think I would be fine drilling and tapping threads into the stock manifold to install EGT sensors? I've heard cast iron is brittle and I don't want to crack it.

Thanks

 

It's thick cast iron, you won't be able to crack it. I would start with a small bit and work up to progressively larger bits.

Also I'd read up on rotary EGT probes - many probes can't take the heat.

Dale

 

So I installed the Pineapple racing dual probes in to my stock turbo set up. You have to be precise with where you put them, but it will work just fine. With that said, I ran the probe holders in with copper anti seize and tried to pull them out today (Roughly two years later) and snapped both out. They're pretty much installed forever once you do it. Nickel anti seize has a higher heat rating and you could try that but just be aware. Good luck with the drilling and tapping!

https://www.rx7club.com/build-thread.../#post12118449

The pictures of them are still in my build thread luckily. The probes still work to this day even after a few track days and lots of street driving.

 

I did this for a Series 5 FC Turbo II manifold. Came out great.