I have always had a hard time getting ring type cylinder head temp senders installed correctly. I was looking around online and found a post on samba regarding this issue. Below is a picture from that post. What do you think?

another

thats exactly how i did mine.

It is done according to the german supply how-to article. They did it slightly wrong there as you are supposed to cut the washer off the spark plug, using the ring terminal as the washer - which keeps all the spark plugs seated in the head the same depth.

It is surprising how much needs to be taken out to fit it as I have done this. But it does work pretty good - you will destroy the $30 thermocoupler wire every time you take out that plug otherwise.

The use of a platinum plug in the illustration destroys the credibility of the author ..................

The Cap'n

LOL- For the record, that was not me. I just hijacked the picture off of samba.

That is what I have done with my heads for the CHT leads.
And, yeah. Gotta get rid if the washer on the spark plug.
Zach

Can the notch be made if the motor is in the car ? I installed a CHT several months ago but haven't done a spark plug change yet..

Can it? Sure. If you have a grinder that will get down there, there is not much stopping you.

Should it? No.

You don't want metal shavings in your combustion chamber do you? Or grinding against your fuel lines?

Zach

You forgot "you don't wanna slip and cut into the spark plug sealing surface, do you"?

The Cap'n

One of my favorite tools is a small die grinder with a tungsten carbide burr. It cuts sort of like a very small Jedi light saber. A very, very small one . One *could* do the cut with a scrap spark plug or bolt in the hole and then thoroughly blow out the shavings with air. Or as an alternative add grease to the plug or bolt to catch the shavings. With care it might end up pretty comparable to pulling a plug after driving on dirty road surfaces - except for the aluminum may be softer than grit.

I installed and grooved mine while the engine was in the car. A friend had made a plug out of a modified a spark plug. He modified the spark plug by cutting it in half and making a screw driver slot out of expoy. Worked great to keep the shavings out of the cylinder. Shop vac and compressor to clean up.

I did this modification last night. My engine is outside of the car however I can see how this could be safely done with the engine in the car (however would be a pain). The tin needs to be removed. I used a wooden dowel to block the plug hole- I actually just screwed it into the hole. I also put vaseline on the dowel to help catch any shavings. I carefully ground down the material making sure to not hit the sealing surface. After finished, I backed out the dowel, most of the shavings stuck to the vaseline. The rest I just cleaned with a rag. No shavings in the plug hole.

Thanks for posting those photos. I need to do this and never was completely sure how it was done. Thanks.

I'd like to do this too. But first I need to find a thermocouple that fits our spark plugs. The one I got with my VDO gauge had to be reamed out to fit over the spark plug. But its gotten so mangled now I doubt its even close to accurate (I know they aren't all that accurate in the first place). Can anyone suggest a place to get the correct size for the plugs in a 1.7?

good luck finding a 14mm ring terminal. if you find em let us know. i have been reaming 12mm ones with a spud bar to spread them open to 14mm. its better than drilling in my opinion.

But still may have an impact on accuracy, correct?

nope, it all depends on the type of gauge you use. the "themalcouples" are just crimped ring terminals....

All the 12mm ring t/cs from aircraft insrument mfrs are just 1/2" ring terminals,
and the 14mm ones are just reamed out 1/2" ring terminals.

Got it. I thought that the gauges were calibrated to the terminal though, or vice versa? As in, you could replace just the terminal with one that was drilled or spread out to 14 mm, but it would impact the readings of the gauge or the electrical signal sent to it, resulting from the temperature seen at the ring.

Nope.
The ring terminal is only a thermally conductive end for the thermocouple wires, which are typically welded together in a carbon arc. The weld bead is crimped in the terminal.

i just stick my wires in the end of the terminal and smash them in my press...