Measuring engine temperature, No taco sender or gauge ... Options

[Chaznaster]

Hello all. With the weather getting warmer, I have started thinking about getting a handle on my engine temperature. I looked at quite a few discussions on here and most were about interpreting/ calibrating the stock(ish) gauges.

I have no sender at the taco plate and no gauge.

I happened on the approach to measure with a dipstick thermometer but it appears those are all NLA.

I have a 123 dizzy that transmits temperature but am pretty sure the base of that is far away from the sump and probably not an accurate reading.

A few questions:
* Is the 123 temperature value good for anything? Maybe there is a conversion? Although I expect it will warm slower and cool faster than the sump in the best case.
* What is the most straightforward way (I am OK with some spend and even running wires to the dash) to get a reliable reading? Gauge (VDO or other), thermal camera pointed at the oil pan? Other?

I appreciate your guidance ...

[930cabman]

Is anyone using the tapped hole the factory used for the CHT sender? Seems like an easy location to grab the head temp

[GregAmy]

Hmm - so the thermocouple ring has a shank where the wire attaches. Does the shank not clear the bottom of the spark plug?

The spark plug hole is spot-faced into the casting, leaving a ledge around its perimeter. That ledge must be notched.

Is anyone using the tapped hole the factory used for the CHT sender? Seems like an easy location to grab the head temp

Nowhere near as responsive and accurate as the spark plug, because much more mass of casting between that spot and the combustion chamber. Plus, the stock CHT location is getting some cooling airflow.

I use the stock CHT location with my Megasquirt setup for "warm up adjustment", but I log actual CHT using the spark plug thermocouple. The spark plug location is very responsive to throttle and mixture adjustments, like almost "right now" where the CHT is sloooooow to react. Further, the actual number I read on the CHT spot is about 75-100 degrees cooler at times than the spark plug.

Finally, all prior history of discussions of Cylinder Heat Temperature (such as the Raby link above) are done in the context of the spark plug thermocouple.

So "CHT" is good for warm-up adjustments, but spark plug temp gives you the best real time status and tuning info.

GA

[barefoot]

[quote name='GregAmy' date='May 26 2022, 10:54 AM' post='3004275']
[quote name='Lockwodo' post='3004265' date='May 26 2022, 10:08 AM']
Hmm - so the thermocouple ring has a shank where the wire attaches. Does the shank not clear the bottom of the spark plug?[/quote]
The spark plug hole is spot-faced into the casting, leaving a ledge around its perimeter. That ledge must be notched.



see this: I made a little clip from some SS sheet metal.