O2 sensor thread tap

[b4black]

I have an old cast iron manifold that I want to add a oxygen sensor to. It already has a boss.

What is the drill and tap size I need for a stock oxygen sensor?

Any issue with drill and tapping cast iron?


Thanks!

 

[KendallF]

18x1.5mm..just go slow and use some tap fluid or oil.

 

[ChrisCairns]

I measured an 18mm tap I have. Then used my handy dandy drill/tap chart and it looks like the 21/32 drill bit should do nicely for the hole.

(First drill a test hole into some junk stock and tap it just to make sure )

 

[b4black]

Thanks! Just what I needed. I'll be off the hardware store tomorrow.

No more cracked headers for me.