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Tapping Cold Start Injector hole for IAT


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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
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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
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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.

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