? about EGT TC install

[TFlory]

I need to know if this is right- I bought a 1/8 NPT-27 tap and 21/64 bit. (. 32). Is that right, or do I have to buy the 'Q' bit.

Also, any pics of TC install locations?

TIM

 

[LotusGT69]

According to my "recommended tap drill sizes for approximately 75% depth of thread" chart you should be using an "R" size drill. the 21/64 is . 3281 in size. the "Q" is . 332 and the "R" is . 339. ideally you would want a special taper drill but they aren't cheap and are hard to find. at our shop we use the taper drill and then we mill the thread instead of rigid tapping it.



this is all assuing that the drill will make the hole you want. unless you are taking it off and putting it on a drill press, be carefull your drill doens't start walking on you cause then you might get an oversized hole.



i also think you should post this question in the 3rd gen engine and transmission forum.



luke

 

[DCreed]

best answers from 3rd gen or comp forum.

 

[TFlory]

OK- I'll ask in the other forum.

 

[dpuckett]

As soft as the stock Cummins manifolds are, I use a 5/16 for 1/8NPT; 7/16 bit for 1/4NPT taps. I use ViceGrips on the tap and have had no isues with threads or exhaust leaks (at least from the t-couple hole). I wouldnt waste good time and effort trying to find just the right size bit.



It should say on the tap (or packaging) what size bit to use.



Daniel