<VV> Thermister

[Sethracer at aol.com]

In a message dated 9/27/2005 8:28:43 PM Pacific Daylight Time, pp2 at 6007.us  
writes:

I bought  a dual Cylinder Head Temperature gauge from Westach that came with 
two  thermocouples and which I plan to put one on the plug for cyl 2 and the  
other for cyl 5 (which are supposed to run hotter than the others) . Was  
thinking about using the factory mounts on each head untill Smitty  
mentioned the effect of the temp under the head on insulation (  
thermocouple cables are 4 feet long and appear to be armored - would  expect 
them to be good for the range of the instrument though - 700  degrees F. 
Would like to hear from people who have mounted in either  place.


I mounted the Thermocouples on the heads in the location originally used  for 
the Thermistor (on the left) and the snap switch (on the right). I  found it 
very easy to wire up, using a 3/8 ID ring terminal and trimmed-off  
socket-head screws, instead of the 14mm plug sized ends. That location is much  more 
responsive in terms of a fast indicator of temp problems, than the location  
under the plug. It is right next to the exhaust valve seat. On 110 heads, it is  
an easy install, since the threads are coarse into the head, and much more  
likely to give-up their occupant. On the 140 heads, (and 150-180s for that  
matter), the threads are 3/8 fine. Removal of the stock thermistor and switch is  
"problematic" at best, and you may, indeed find yourself with broken-off parts  
or "threadless" holes left over. The thermocouple wires are designed to "take 
 the heat" in that application, I wouldn't worry about them. Using them under 
the  plugs - I suppose in lieu of the original plug gasket - might have some 
effect  on the actual heat range of those plugs. Something to consider. The  
best installation I ever saw, and the most work, was done by Doug Hargrove of  
Modesto, CA. Doug drilled out the centers of some small-hex bolts, commonly 
used  as "header bolts", pushed the thermocouple wires through the bolt, 
installed a  spring and a retainer on the wire tip and screwed it into the head. The 
actual  thermocouple junction was pushed up against the end of the hole in the 
 head, contacting the cylinder head metal a fraction of an inch from the 
exhaust  seat portion of the head. When anything happened, Doug knew immediately. 
- Seth  Emerson