Hi, fellow rotary enthusiasts....I am in need of a little 
help regarding the fitting just underneath the oil filter on my 1989
13b turbo engine.  When I originally received the engine 
from another builder, it was going to be mounted plugs up, 
and he had
inserted the tube and 
radiator cap shown in picture number one.  
Picture number two shows the hole it came out of.  It was not
even a press fit, it pulled out easily, with very 
little effort. I plan on using this hole for sending 
water to my heater core.
I was hoping others have found a successful solution 
for this fitting/hole.  It measures .670".  
A 1/2-14 NPT pipe requires a
23/32 hole, which would open the hole to approximately 0.718.  
I'm afraid that there would not be very much material left after
drilling this and attempting to tap it with the pipe tap.  
I might be able to turn a sleeve on my lathe that would terminate
with a 3/8 female NPT, which I could tap into the hole.  
Any other suggestions or remedies?  Thanks in advance for your
replies.   Paul Conner....engine turns over now....hook up
 radiator and oil cooler, and we'll see if she runs.

The hole size is almost perfect for a 11/16 24 straight thread.
A bolt will then seal the hole. If necessary you can then drill
and tap the bolt for 1/4 NPT.

Or... how about a steel plug high temp epoxied in with a small set 
screw installed  from the front side to mechanically lock in the 
plug/ 1/4 NPT adapter?

Paul Lamar
 
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