I'm about to install my pyro & boost gauges. The autometer guys tell me to use 11/32" drill for both when tapping. I see no prob. with the pyro. but the boost fitting is quite a bit larger (like needing to use 1/2" drill). I'm not sure if they understand that my 89 is non-intercooled and will be tapping into the cross over tube from the compressor. Can anyone help me out please. ???

 

That 11/32 (.343&quot tap drill sounds like it's for 1/8" NPT. 7/16 (.4375&quot tap drill is for 1/4" NPT. If in doubt, check local hardware store for a thread gauge. I know when I installed my pyrometer probe, it was 1/8" NPT. On my ISB for the boost, I just removed the plug on the side of the engine and didn't have to run any threads. Hope this helps. Happy New Year!

 

There is no sense tapping the pressure side of the air system. Just go to the top of the intake manifold and pull one of the plugs already installed for that purpose.

 

Well that makes sense. Some directions I got told me to tap the boost tube. Glad I asked.

 

Where is this plug, I looked on my 99 and I see 3 larger plugs and 1 smaller one on the top of the engine by the manifold. Is one of these what your talking about?

 

Check here and see if this helps.<br>Boost install near bottom of page.<br>http://www.showmestate.org/stltdr/ho...T_how_to.shtml

 

Unfortunately my 89 is alot different, and the only thing I see for a plug looks like a tranny drian plug underneath the manifold (38&quot; insert and a PIA to get to). I pulled out all the bolts on my manifold looking for something and got nothing. Directions I found said to drill and tap boost tube for the 89 and that sounds pretty good about now.