[APWCU]

I'm getting ready to install some gauges in my truck and was wondering what size drill bit to use to drill in the exhaust manifold. I know you use the 1/8npt to thread just not what size drill bit. Any help would be great. Thanks.

 

[glfredrick]

http://www.engineersedge.com/manufacturing/pipe-tap-drill-chart.htm

Good chart on that site ^^^.

Oh, if you don't have an "R" drill bit, the inch size is .332. Find the closest bit to that size. 21/64 and 11/32 are the bits on either side of an "R".

 

[Bunker Buster]

11/32 works good for a 1/8" pipe tap.

 

[WUTNOIZE]

i just did mine ... i used the r bit but i found it too small so i went to the 11/32 ng so 21/64 worked great ...nice tip on the install plug up youe exhaust 90% and start the engine let idle and start your drilling wear goggles cuz the metal flies up at u dont let the exhaust get hot so shut it down between the drilling and tapping ..but run it when u tap it also ....works great

 

[lastcall190]

I used an R bit and a 1/8-27 NPT tap with great success. When drilling I went slow to make sure I was at a right angle with the manifold. Once you get going, the manifold seems real soft. I used a big magnet then after the hole was drilled I put a screwdriver in the hole and picked up the shavings. It was one of them screwdrivers with a light magnetic force, and it picked up a ton of stuff. When tapping, go a little ways, then back out. Then back in a little more, then back out. I ended up doing about two revolutions of the tap at a time. I got cocky at the end and went more than I should have and busted part of the tap. Luckily the probe adapter threaded nearly all the way in so it was all good. Good luck.

-J

 

[WUTNOIZE]

thats why i went with the bigger bit cuz when i was tapping it it felt too tight for comfort and even with the bigger bit the threads came out perfect...next time u do one try running the motor with the tail pipe blocked 90% ...its a good deal to go

 

[Pri_i_oh]

should make this a sticky...theres some good tips here

 

[WUTNOIZE]

should make this a sticky...theres some good tips here

i think there might be something on this site already..not too sure i know i read it somewhere..and it works sweet:thumbsup:

 

[Pri_i_oh]

this site has so much info that Im still trying to read it all

 

[Luckyr]

Should I drill before the turbo or after?

 

[WUTNOIZE]

pre turbo is most accurate post turbo is a few hundred degress cooler..

 

[DozerDavis]

I just tapped mine I also used the 1/8 th 27 but I went with the 5/16 bit worked great. Please be aware when drilling in the manifold to stay towards the cab side of the middle as in the very center is a webbing hope this helps !

 

[RPegram]

 

[APWCU]

How much of a difference would there be if it was placed in the front half of the manifold?

 

[RPegram]

The rear is the best since the rear can be just a hair higher than front. You want to monitor the absolute worst temps to prevent damage to engine.