<VV> Thermister, two thoughts.

[Tony Underwood]

At 04:16 hours 01/02/2006, you wrote:
>Prelude-  I have a good working original Thermister
>that I just took out of one of the turbo heads I have.
>  the threads are still nice, and the thermister seems
>to work fine as far as I tested it.  the porcelain or
>whatever is in perfect shape and still says AC very
>clearly.
>
>So my questions are this...
>
>One- is there any easy way to adapt a thermister to
>work on my 110?




The easy way:

Since the snap switch screws into a relatively shallow 3/8X16 hole, 
and the thermistor is longer than the snap switch stud, you'll need 
to drill the hole a bit deeper to accommodate the brass cylinder 
extending past the threaded section of the thermistor.

Select a drill that's just *slightly* larger in diameter than the 
brass cylinder portion of the thermistor.   Measure 
*Carefully*.   Drill the current threaded hole in the cylinder head 
to appx 1/8" deeper than the carefully measured length of the brass 
portion of the thermistor as measured from the face of the flange to 
the end of the cylinder.    Do NOT drill any deeper than that or you 
could possibly drill into the combustion chamber.    It's not 
necessary for this extra length of hole to be threaded.   Only the 
existing threaded length of the hole is at issue.

When the hole is deepened accordingly, acquire a 3/8X24 tap and 
simply "cross-thread" the tap through the existing 3/8X16 
threads.  Again, you need not thread the hole any deeper than the 
existing 3/8X16 threads.   In spite of how flaky this sounds, it will 
work.   The thermistor will screw into the new threads and snug up 
without any difficulties.   I've done this twice on 95hp heads for 
turbo engines, no problems.    Don't twist down hard when you screw 
the thermistor into the head.   It only needs to be snugged... and if 
you crank down on it too hard, you can snap the threaded section and 
break it off in the head.   Likewise the business end of the 
thermistor where the wire attaches.   It's very easy to break.


The entire procedure, once you have the lower shroud off and have 
tools in hand, will only take about 5 minutes.


tony..