There are 2 bolt holes in the rear or the passenger side cylinder head. I'm wondering if any of you know the thread size of the one closest to the exhaust manifold? Its the coolant passage hole. I'm trying to find a special fitting.

 

M6x1x30

 

I found where it is a M12 x 1.5 ??

 

Are you talking about these holes? (first pic)
If yes, the steam tubing fittings go like this (pic 2)
And the bolt size is M6x1x30.

 

He is referring to the hole that is used for a stock sending unit location. That is in the front on the driver's head but unused and plugged towards the rear of the passenger head. I thought those holes were like 1/4 NPT for the sending units but I could be wrong.

 

If he's talking about the temperature sending unit ports, the thread is M12x1.5. Seen here with an adapter in it:

 

Thanks, Steve.

Paul: yep, that's the one. Thanks guys.