what would be considered typical operating ranges for 1) oil temp 2) head temp gauge assuming normal operating conditions/load

I think oil temp should be 180-210 F; 180 warmed up and 210 after a spirited drive, 220 on a hot day with a spirited drive. These are temps I got with an analog thermometer from Mainely Custom by Design down the dipstick tube. Head temps 350-400 F are on the hot side but I've seen these on my VDO CHT gauge, cylinder #3 track driving; actually, maybe a little higher 425ish. I think Jake will say my heads have melted at that temp.

thanks jim. I might have an issue with the senders or gauges. I'm getting 125-150 max for oil and 250-275 head temp...pushing 300 if very hot outside and running hard

For the oil gauge I would be willing to put money down that you have the old style long sender, and I know you are using the new style 2 1/16 inch gauge. You need to be using the modern sender, but that is an easy fix.

For the head temp gauge it looked like you were using the thermocouple on plug wire three (which is correct). But it might be the wrong thermocouple, or the wire to the gauge may have been cut. The thermocouple is pre-set for a certain wire length and a longer, shorter, or cut and mended wire will give you inaccurate results. I would buy a new thermocouple (one that matches your gauge). The thermocouple wire to the gauge should be one single run, not use any existing wires, and the only breaks in it should come from the factory and be joined by the factory connections.

Zach

nice link to gauge discussion:

http://www.ratwell.com/technical/VDOGauges.html#cht

germansupply.com has sender only for sale at ~$22

Huh, based on that article, Bill's gauges should be running a little hotter, not considerably ~100degrees cooler.

Zach

Any cold joint in a TC set up changes values drastically. Wire color of the thermocouple wire will tel you what one it is.

http://www.omega.com/techref/thermcolorcodes.html

Oil temp gauge info.

with a thermocouple, when it is hot in the cabin where the gage is, you will read lower head temps then when cold at the gage. the thermocouple indicates the difference in temperature between the sensor end (junction) and the gage. some fancy gages have compensation for different ambient temps. the standard VDO ones do not. so you may find you "run cooler" on a hot day that is becuase the gage is hot and the difference is lower between gage and sender.

If I remember my install, the only junction that I saw (so the other junction is inside the gauge?) was at the sender which is under the spark plug and the sensor is connected to the wire harness for the gauge set. So what you're saying is on a hot day, like on the track in the summer, the head temps are actually HIGHER (!) than indicated on the gauge?

The thermocouple wire works from making a very low voltage from dissimilar metals ( ie MV range). The wire length does make a difference, and any time a thermocouple is attached to a standard non TC wire, or non TC terminal like a screw terminal, that is a cold joint. Since we are talking small MV output, any change in resistance makes a big difference on the gauge. I don't use a VDO type, so i'm not sure what exactly they did, but I would guess it is a TC extension lead from the gauge, to a TC on the cylinder. You can buy bulk TC wire but it is a little $$.

Yes!!!! the TC reads the difference in temps between teh junction at sendor and the gage end. Most are calibrated to be right at roughly a 70F ambeint temp if your reads correct at 70F then at 90F it will read 20 degrees lower and at 50F it will read 20F too high. (assuming same head temp)

dang it, then I might be seeing 450 F head temps at the track. Don't tell Jake...

You run track days when it is 45 degrees outside?

Look at the chart on the link you posted. If you are doing things in the summer, then your VDO is reading too high and your engine is cooler then indicated. If you are doing things in the winter then your VDO will be reading too low and the engine is warmer then indicated.

Or, you could just get a temp compensated gauge and not have to worry about it.

Aircraft Spruce, By the way, sells a temp compensated CHT that looks a lot more like the VDO, and you can read the CHT of two cylinders at once with it. I would consider it if I did not already have my digital one.

Zach

Great stuff guys - thanks. I'm still interpreting the link articles but should be an electrical engineer in no time

If I understand correctly - it sounds like I likely have a mismatch between the newer oil temp gauge and an old style sender. And with the head temp, I may have a bad or mismatched thermal coupler or damaged wire? Do I have this right

Regarding the temp ranges, any one else able to provide the typical operating ranges I should expect for each assuming a correct set-up?

I guess it would be smart to read links I posted, DOH! I'd like it if my CHT was reading too high

my Type One motor does about 320-380 head temp using a non-compensated VDO gage spark plug style sendor. about 350f is normal cruising for me at 65 mph on the flats. it will peak out near 400 on freeway dashes up hill, but quikly drop back after letting up on the gas or cresting the hill. these readings are typical for a 70-80F ambeint temp. the head temp will very a good bit with driving condtions, fast responce time.

thanks realred

For a stock 914... Here's all you really need to know: (added to illustration)

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