installing CHT, alternate locations? Options

[914 RZ-1]

I'd like to put a CHT (Aircraft Spruce, most likely) on my engine, but it seems the spark plug location requires either some grinding of metal, which requires removing a bunch of stuff, that requires removing the engine, etc...
Is there another place to install a CHT? There is a CHT sensor on the engine, but doesn't that have to stay? Or, can I attach a gauge to that one?

The only alternative I was able to find was this thread (thanks 76-914) about bending the wire 90 degrees on the spark plug install option:

"Like Mark said it's just a piece of metal so open it up a bit so that the plug rotates freely in the ring. Then with the ring on the plug bend it 90 degress. Now turn the plug again to be sure that it rotates freely after the bend. Insert plug into #3 with the wire at the 9 o'clock position (or towards the rear) and tighten. There seems to be a bit more room for the lead when installed in this position. at least my head had a bit more room to the left side of the plug. BTW, I left the plug washer on so I would not twist the sender."

[Rand]

cylinder 3.
No reason to question it.

[Mark Henry]

Under the plug or it's a useless reading.

[914 RZ-1]

So bending the piece that goes around the sparkplug 90 degrees is the best way? I DO NOT want to grind any metal around the hole!

[michael7810]

So bending the piece that goes around the sparkplug 90 degrees is the best way? I DO NOT want to grind any metal around the hole!

It can work but be very careful, I destroyed 1 sensor doing it this way. The trick may be to use a thin plug socket because when you bend the wire up 90 degrees it can clear the plug OK but in my case the socket pushed the wire tab out and it ground into the plug recess. It worked OK but when I removed the plug the ring was damage beyond use. It did not damage the head. Eventually I removed the engine and hogged out the plug recess on 1 side and now plug installation and removal is no different than without a CHT.

[914 RZ-1]

Thnx for the tip. I was hoping to avoid hogging out metal.

Would it be a good idea to find a smaller ring to fit around the plug? Could I modify it to fit?

I guess I could buy a cheap socket and machine out a hole/slot that accommodates the bent part of the ring? Then I run the risk of dropping the plug when I pull it out.

So bending the piece that goes around the sparkplug 90 degrees is the best way? I DO NOT want to grind any metal around the hole!

It can work but be very careful, I destroyed 1 sensor doing it this way. The trick may be to use a thin plug socket because when you bend the wire up 90 degrees it can clear the plug OK but in my case the socket pushed the wire tab out and it ground into the plug recess. It worked OK but when I removed the plug the ring was damage beyond use. It did not damage the head. Eventually I removed the engine and hogged out the plug recess on 1 side and now plug installation and removal is no different than without a CHT.

[Porschef]

There's an alternative, I also didnt want to bend it and have it coming up thru the spark plug hole/grommet so I drilled a hole perpendicular to the plug and installed it with a grommet.




Like everyone has said, put it under #3 plug.

[michael7810]

Thnx for the tip. I was hoping to avoid hogging out metal.


I guess I could buy a cheap socket and machine out a hole/slot that accommodates the bent part of the ring? Then I run the risk of dropping the plug when I pull it out.

That might work. Just be careful...I imagine a bunch of guys have installed CHTs without hogging out the head so it can be done. I have the rings on #s 1 & 3 plugs and only destroyed one (IMG:style_emoticons/default/blink.gif)

[barefoot]

The proper relief for an under the plug TC:

[maf914]

Barefoot,

Thank you for the helpful photos. This is something I need to do.

The photos show a metal clip locating the sensor wire to a cooling fin. Could you say where you obtained this clip or how you made it? Thanks.

[Mark Henry]

You don't have to make the grove that big, I cut a notch and bend the ring at a little better than a 45*.

[barefoot]

Barefoot,

Thank you for the helpful photos. This is something I need to do.

The photos show a metal clip locating the sensor wire to a cooling fin. Could you say where you obtained this clip or how you made it? Thanks.

Sorry, not my photos, I will make some clips from stainless sheet metal when I'm at the assembly stage. I'm thinking where to bring the TC leads out thru the top tins, will need some small grommets which you can now get at Lowes or Home depot.