I need to know what the thread size is for the two oil gallery plugs on the back of the block just behind the heads (one on each side).

The machine shop took them out and I didn't realize it. That's where my big oil leak is coming from when I try to start the damn thing.

They feel like (can't see 'em) 1/8" NPT, but the 1/8" plugs I have aren't wanting to thread in there. I can't imagine that they'd be any other size, but I'd like some confirmation on it before I go running a tap through them.

Thanks.....

 

A futile TTT for this one.........

 

The best I can tell, it says they are .250-18. GM PART # 12338136 if you think you want to try that. Says there are 4 of them.

 

Is that 1/4" by 18 then? That's odd that it'd be something other than just a standard NPT fitting.

4 of them, huh.......wonder where the other 2 are then. I'll try that part number out at the dealer though.....thanks.

 

are you talking about like where the oil pressure sending unit plugs in? That hole is right behind the drivers side head. If so they are 1/8 in. pipe.

 

I know, but that was the way it was written in the parts book. <shrug> There is not any detail for that in the book. I gave you all that info because I don't really know, myself. Hope something works out.