Jump to content

Tapping Cold Start Injector hole for IAT

Recommended Posts

Quick question I figured I would ask. I bought a 37/64 drill bit and drilled out my cold start injector hole so I could tap it for the intake air temp sensor for my MegaSquirt setup. Well I got all that done, but I see there's not really a whole lot of actual thread area for the sensor to grab. Anyway I can thread my sensor, and it doesn't seem to get tight until it's pretty much all the way in. I took a little 3/8 npt plug and although I didn't go all the way with it, it seemed like if I wanted to I could just keep on threading it all the way through til it fell out. It never felt like it got tight like you normally get with NPT threads. I don't know if I have a bad tap, or I did something wrong or what. Can I still get a decent seal? I haven't tested it yet, but I got the thread sealer that I used for my fuel rail, made sure the sensor and threads in the intake were clean, then threaded the sensor in and out a couple times to really work the sealant into the threads then hand tightened it and gave it maybe a 1/4-1/2 turn. So we shall see. I'm not sure if this is something anyone else has run into?


I think I realize what I did wrong. I ran the tap til it pretty much bottomed. I didn't realize you're supposed to actually stop a lot sooner to provide the taper. Hopefully the sealant will allow an actual seal?

Edited by DuoWing
Link to post
Share on other sites

NPT threads that size are designed to be sealed at 1/4-3/4 turn past finger tight.

Use some Loctite 567 or similar, go no more than 3/4 turn from finger-tight and let the sensor set for two hours before you pressurize it...I'll wager that will be Helium Bubble Free Sealed to 10Bar.


I put my IAT sensor in my 60mm TB Adapter Plate. Lots of meat there to tap!


I used the Cold Start Injector hole and flanged fitting as a Idle Air Bypass Entrance for setting up the idle speed.

Edited by Tony D
Link to post
Share on other sites

I use a 9/16" drill bit for 3/8" NPT holes.


As you found out, in thinner materials you need to cut the thread a little at at time and check with an NPT part or pipe, for depth of fit.


I used that exact same location for my MAT sensor as well. IIRC I don't think I actually needed to drill it, I think it was close enough to start with, Then again that was 6 years ago, so the details are a bit fuzzy.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...