Im about to install my boost sensor. It calls for 1/8 NPT threading. I have a 1/8 NPT tap but im not sure i have the appropriate drill bit size. for 1/8 is calls for size "R" but i dont have this. However and 11/32 bit has a diameter of like .3428 and the R has .3390. couls this less than one-hundreth of a difference make it not work. or any other ideas would be appreciated. Thanks Ryan

Should be fine, I used a 5/16", the tap will make it right.

Go for it. Just be carefull with the tap. Ease it in and out. Be carefull not to break the tap.

2-4 turns in back out till it turns free again and repeat

That size will work and is probably better than the R. The casting is only 1/8" thick.

5/16 is the size to use and make sure it is magnetic.

5/16 is the size to use and make sure it is magnetic.Magnetic Aluminum? I have heard of Clear Aluminum but not magnetic:)
I know what you were refering to, the exhaust manifold, but I think he is tapping his boost gage fitting into the intake housing.

Use a 11/32 drill, DO NOT USE A 5/16 DRILL, THAT IS WAY TO SMALL.
Pack the drill flutes with grease and drill away. Don't run the tap in all the way, if you bottom out the threads on your fitting, the thread will not seal. also pack flutes with grease.

Run the tap in about half way, clean out hole, run your fitting in hand tight, back out, counting the #of turns, then count how many threads are on your fitting.
you want to stay 2-2.5 threads short of bottoming the fitting. If you need to go an additional 3 threads, rerun the tap in 3 full turns from where the tap stopped.

The .004 oversize you will be drilling your hole isn't even an issue.
The chance that you break the tap by drilling a 5/16 hole is greatly increased.

I've been a machinst for 9 years and broke my share of taps. Trust me, not fun drilling out a tap especially with a hand drill.

Magnetic Aluminum? I have heard of Clear Aluminum but not magnetic:)
I know what you were refering to, the exhaust manifold, but I think he is tapping his boost gage fitting into the intake housing.


Who said anything about magnetic aluminum, he was talking about the drill.

Use a 11/32 drill, DO NOT USE A 5/16 DRILL, THAT IS WAY TO SMALL.
Pack the drill flutes with grease and drill away. Don't run the tap in all the way, if you bottom out the threads on your fitting, the thread will not seal. also pack flutes with grease.

Run the tap in about half way, clean out hole, run your fitting in hand tight, back out, counting the #of turns, then count how many threads are on your fitting.
you want to stay 2-2.5 threads short of bottoming the fitting. If you need to go an additional 3 threads, rerun the tap in 3 full turns from where the tap stopped.

The .004 oversize you will be drilling your hole isn't even an issue.
The chance that you break the tap by drilling a 5/16 hole is greatly increased.

I've been a machinst for 9 years and broke my share of taps. Trust me, not fun drilling out a tap especially with a hand drill.What he said.
Plus we use a ram type EDM to burn taps out. Also our hole burner work well to. I've been a toolmaker for 25+ years!

Who said anything about magnetic aluminum, he was talking about the drill.The base material that he was drilling is aluminum. How would making sure the drill/tap is magnetic have any bearing on this? The grease I can see. Plus I was just being funny;)

Who said anything about magnetic aluminum, he was talking about the drill.
Sorry, I reread the question, and your right he tapping the intake, not the exhaust:confused:

I have a lb7 and there was no tapping needed in the intake. so i assumed he was drilling and tapping the exhaust manifold.

making an a$$ out of you and me:D

Sorry, I reread the question, and your right he tapping the intake, not the exhaust:confused:

I have a lb7 and there was no tapping needed in the intake. so i assumed he was drilling and tapping the exhaust manifold.

making an a$$ out of you and me:D:Moon: :Handshake :beerchug:

Do a search for the "hoot method" and go for it.

I did this afternoon and it worked like a champ.

I used a 21/64 drill per instructions and had no problems.

Yes, sorry for not being clear, I tapped the manifold and put the EGT sensor there. (I misread that he was installing Boost sensor...oops) I installed the EGT probe that came witht he Attitude monitor and used a 5/16" drill (magnetic) :D and then the 1/8" npt tap. Worked perfect.