There are 3 ports on the front of the TPiS Bigmouth base. 1 gets a coolant nipple, 1 gets a coolant sensor, and the other gets plugged. Those of you that have the bigmouth base, what did you use to plug it? Size? Pitch?

Its a pipe thread....can't remember..either 3/8" or 1/2" pipe plug

Hmmm. It is a large passage.

I measure it up as a 9/16" hole. Does that sound right to you?

correct it is 9/16", but npt sizes are way different, you need a 3/8" NPT plug for that hole. most parts stores carry these, even hardware store for under a buck.

Correct, 338 NPT. I used an autometer brass plug with a 1/8 NPT thread in the center so I could run an autometer water temp guage.

I got a 3/8 npt plug today. Talk about tight. I can barely get the thing started. I wonder if my casting is bad. I had to grind a big of metal away from around the vacuum port just to get that nipple in.

It should go in just dont try to force it in all at once. Back it off a few times with some teflon and it should go in. It wouldnt hurt to run a tap through first.

I put my fan switch in that third hole, and extended the wires to it. That keeps it away from the headers and keeps the connector from getting brittle and breaking.
Then just plug the hole in the head.

I like that idea, Im going to steal it!!