What size NPT thread is the heater hose fitting?

[MoparMike1974]

I have an RPM airgap intake and I need a second hole the size of the heater hose fitting. Im installing an MSD Atomic efi and need to install the temp sender. My intake has two extra plugs but they are too small. Fortunately one has a boss large enough to drill and tap to the larger size.
Edelbrock Performer RPM Air-Gap Intake Manifolds 7576
Interesting that the picture summit shows has two of the larger holes.
Can anyone confirm what size tap I need for this?

 

[MoparMike1974]

Looks like its 3/8 - 18 NPT.

 

[67Dart273]

OD of US pipe sizes

Pipe Sizes Information

A straight "regular" water pipe nipple in 3/8 is about right for 5/8 heater hose. 1/2 pipe is more like 7/8, 3/4 pipe is over an inch OD

 

[67Dart273]

OD of US pipe sizes

Pipe Sizes Information

A straight "regular" water pipe nipple in 3/8 is about right for 5/8 heater hose. 1/2 pipe is more like 7/8, 3/4 pipe is over an inch OD

 

[MoparMike1974]

Got it. I was able to remove the thermostat and stick a vacuum cleaner hose in there to suck out the chips while I drilled and tapped the hole. Worked like a champ. Now I have my temp sensor installed for my Atomic EFI.