I am using a VDO oil pressure sender and need to tap the hole for 1/8 NPT threads.  I believe the Mazda unit is also 1/8 NPT.  For some reason a 1/8 NPT nipple will not thread into the hole.  I ran the tap in to clean out the hole but no luck.  My theory is the the oil passage at the area i too small to let the tap go in far enough for a standard 1/8 NPT nipple to seat properly.  May have to trim the tap.  There seems to be a hole close by that could line up with the water jacket.  Could I use it for water pressure monitoring?  Appreciate any input.
 
Joe Berki
Limo EZ