What should I put in this hole???
 

I thought that would get your attention. :)

I don't recall having anything in this hole before the rebuild but I feel like there is supposed to be something here. At least a plug right??

This is just above the rear trailing plug.

http://i721.photobucket.com/albums/w...7/5adbbad2.jpg

Knock sensor.

Although it is usually on the front housing, not an issue on the rear.

Some people actually recommend it.

It's useful as long as you know the baseline for your engine. Before my rebuild mine was around 30ish max, then went to hang out in the 60's and 70's before the engine lost compression due to a chipped seal (found out during rebuild).

New engine sits in single to low teens, but like I said every engine is different and other things rattling around in the engine bay can of course give high readings.

It helps if you have a power fc to easily monitor it via the commander.

Since I have my knock sensor in the one above the front trailing plug, I just need to plug this one correct? Is it a 1/8th NPT thread?

You don't need to plug it.

Thanks Mahjik