Question about taping for boost gauge.
 

I have an Autometer boost gauge 4305. And I know I need to install in into the pipe going into the intake.

My question is, what size hole do I need to drill? and what size tap is needed? Is it a NPT tap? I am clueless on this I have never taped anything before. I do have a set of metric and SAE tap and die sets but I don't think they will work.

Thanks in advance for the help.

most are 1/8" npt but check the transducer that came with your gauge to be sure.

Its not electrical, it mechanical.

So do I need an 1/8" drill bit and 1/8 NPT tap?

You need an 1/8 NPT tap but the drill size is difference. The drill size should be listed on the tap. DO NOT GO BIGGER on the drill size or you won't have enough threads to hold the fitting in the elbow, which is only pot metal and fairly soft. Give me a few minutes and I'll go look in my set to find the correct size for you.

Wouldn't you know it??? All my taps list a drill size EXCEPT the 1/8 pipe, which is NOT 1/8"

Thanks! Where can I get the tap? Lowes or an autoparts store?

Either should have it, but Lowe's is the better choice to have everything you need drill bit wise.

1/8 pipe thread drill size 5/16 decimal .3125 hope this helps.:-wink

Thanks. I read its and R type or .339 or 21/64. Is that the same as what you are saying?

Is it going to be 1/8"-27 NPT tap?

I would go with the 5/16 as it will give you a red hair's more meat when you tap. Remember that the NPT thread is TAPERED and you don't have to go all the way in on the tap to get a big enough hole to thread your fitting into. Leave yourself a little safety but also remember that you're going to be using some kind of thread sealer (liquid better here) that will take up a tad of space.

27 would be threads per inch. match the tap to the fitting you are going to be screwing in. the threads from one should exactly match the threads from the other.

Cool thanks

Best remove the tube before drilling and/or taping. Don't want metal shavings in your engine.

If you have an '04 you probably have the dummy butterfly thingy between inlet elbow and the manifold. It is the thingy that has two electrical connectors attached that do nothing. Instead of drilling the elbow you might want to consider drilling the dummy butterfly thingy. If I remember right, it is square, not round like the inlet. Just food for thought.

DSMMH

Is this butterfly needed? Is it a restriction? Can I remove it?

BTW Went at lunch and got what I needed at Lowes.