Aftermarket Cylinder Head Temp Gauges

SyntheticBlnkerFluid · Thu Nov 24, 2016 10:09 am

So I have been looking at Speedhut's Cylinder head temp gauge as what I want for my Monza build. However, they only go up to 500 degrees. My dad elaborated that you need a 600 degree gauge because the Corvair heads can get up into the 500 degree range easily. So, I plan to contact Speedhut, because they will make custom gauges and see if they can make a 600 degree gauge.

I'm actually surprised that there aren't more options for VW owners, but I can only find VDO (and rebadged VDO) and I have seen several things that say those gauges aren't accurate.

The only other options are aircraft gauges and I'm not a fan of the look of them and the ones I do like have a fixed bezel for aircraft applications.

I'd like a set of vintage Stewart Warners, but those are hard to come by and usually people don't want to give them up.

Oh Corvair owner problems :-P

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lostboy · Post by **lostboy** » Thu Nov 24, 2016 10:12 am

Yeah that's lame. Looks like auto meters only go up to 340.

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lostboy · Post by **lostboy** » Thu Nov 24, 2016 10:13 am

I wonder if you could use a temperature gauge suited for something else... for instance an oven or kiln. You could always reface it to your liking.

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cooterr · Post by **cooterr** » Thu Nov 24, 2016 10:26 am

The Speedhut CHT is a much more accurate gauge with an industrial grade thermocouple. The vdo thermocouple is very rudimentary with a cold junction point that is to close to the thermocouple. I have a VDO installed and it is being replaced by a Speedhut gauge this winter. I think 500 degrees is a satisfactory range for the Corvair. I have not had my car get to that tempurature but mine is not turbo.

Post by **66vairguy** » Thu Nov 24, 2016 10:52 am

It's been written the GM overtemp switches turned on the warning lamp at about 500 F degrees, but 140 HP and turbo cars had a switch (different threads so they can't be mixed up) that activated the lamp at 575 F degrees.

If you read old posts folks tend to report a Corvair engine will climb to 450 - 475 F going up hill on a warm day. So a 500 F maximum gauge is fine, assuming the themocouple is located at the same position as the Corvair snap switch/thermistor location on the head. Some gauges locate the thermocouple ring under a spark plug, not sure what would be considered a maximum temperature at that location.

Yes the old VDO gauges are reported to be inaccurate and I've been told they are no longer sold new. VDO has been in the process of designing a new gauge for the VW, not sure if or when it will be available. The inaccuracies with ALL the cheap thermocouple gauges is a partly a problem called cold junction sensing. Without going into paragraphs to explain, the bottom line is in the last few years new solid state chips now deal with this issue and the newer gauges are better. Just look at the gauge specifications to see if "Cold Junction Compensation" is part of the design.

SyntheticBlnkerFluid · Thu Nov 24, 2016 2:09 pm

Well the other problem is that the Corsa 140 and Turbo thermistor is virtually unobtainium, so with any new gauges you're stuck with a spark plug thermocouple ring.

But you're right that unless we know what the maximum temp is at the spark plug. A 500 degree gauge may be suitable.

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Post by **66vairguy** » Thu Nov 24, 2016 4:22 pm

SyntheticBlnkerFluid wrote:Well the other problem is that the Corsa 140 and Turbo thermistor is virtually unobtainium, so with any new gauges you're stuck with a spark plug thermocouple ring.

But you're right that unless we know what the maximum temp is at the spark plug. A 500 degree gauge may be suitable.

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If you have a Corsa (or Spyder) DO NOT throw out the temperature gauge. My experience is they are well built. The issue is the thermistor (sender) and used ones are still available. The other option is that a few folks are working on an alternative to drive the old Corsa/Spyder gauge. The demand for a reliable accurate driver is growing and someone creative will meet that demand.

Meanwhile if you have a Monza and want to add a gauge then the aftermarket unit you are looking at will be fine for normal driving as sustained head temperatures over 450F are not a good thing - in my opinion.

The Corvair engine rarely overheats during normal driving conditions unless the fan belt breaks and then the rise in temperature is FAST and the GEN/FAN warning lamp is needed to get the drivers attention NOW.

SyntheticBlnkerFluid · Fri Nov 25, 2016 10:14 am

@66vairguy

I have a Corsa dash in my Monza. It does have the CHT gauge. I however want 2 CHT gauges.

The reason I like the Speedhut gauges are because they are programmable and have built in warning lights.

I am aware that the thermistor is still available used, the problem is availability, because there are people hoarding them and then those who want to sell are asking way too much for them (in my opinion) and I would be more than happy to go to spark plug ring style thermistor just for the ease of cost and availability.

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Post by **66vairguy** » Fri Nov 25, 2016 10:50 am

SyntheticBlnkerFluid wrote:@66vairguy

I have a Corsa dash in my Monza. It does have the CHT gauge. I however want 2 CHT gauges.

The reason I like the Speedhut gauges are because they are programmable and have built in warning lights.

I am aware that the thermistor is still available used, the problem is availability, because there are people hoarding them and then those who want to sell are asking way too much for them (in my opinion) and I would be more than happy to go to spark plug ring style thermistor just for the ease of cost and availability.

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I also have the Corsa cluster in my Monzas (four door and convertible) and I did add a second temp gauge in the clock position.

The Speedhut gauges sound like a good solution for you. I like the stock look and didn't want to cut up the cluster too much. If you don't want to keep your old temp gauge, then don't toss it. Drop me note and I'll buy it. As I said there should be a solution to drive the old gauge, but not at the moment.

BTW - Seth Emerson sells aftermarket gauge adapters for the Corsa cluster housing He is easy to reach by phone. See http://www.perfvair.com/dash-parts-steering-columns/

lostboy · Post by **lostboy** » Fri Nov 25, 2016 8:13 pm

Whatever you do, don't let the obsession of gauge monitoring take over the joy of the drive.

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SyntheticBlnkerFluid · Sat Nov 26, 2016 3:30 pm

lostboy wrote:Whatever you do, don't let the obsession of gauge monitoring take over the joy of the drive.

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Well after any build, there should be a little OCD-ness to keep an eye on the gauges to make sure every thing is copacetic, but after you know everything is OK, then by all means enjoy the drive.

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recessbilly · Post by **recessbilly** » Sat Nov 26, 2016 6:49 pm

I know it's not the prettiest, but I made one for less than $20 that is digital and goes to 1200 degrees. It doesn't go with the interior aesthetic, so I keep it in the engine compartment for a monitor of sort. I can make more if anyone is interested.

lostboy · Post by **lostboy** » Sun Nov 27, 2016 6:14 am

recessbilly wrote:I know it's not the prettiest, but I made one for less than $20 that is digital and goes to 1200 degrees. It doesn't go with the interior aesthetic, so I keep it in the engine compartment for a monitor of sort. I can make more if anyone is interested.

Sweet! I was thinking "remote mount infrared" if I really needed one.

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maineyenko · Post by **maineyenko** » Thu Dec 01, 2016 1:17 pm

Howdy, I'd like to take you up on the CHT digital gauge. Currently using VDO CHT with spark plug senders bolted to thermister locations on a 140 ish engine. Do you know if the VDO's with be compatible with your digital gauge?

thanks Ken

wbabst · Post by **wbabst** » Thu Dec 01, 2016 1:56 pm

I have a VDO cylinder head gauge, and I have read all the stuff about them, and how they are not temperature compensated and crude but the fact is they work and work decently well. I have it attached under the spark plug of the number 4 cylinder. I picked that one because the thermoswitch for the idiot light is on the right bank so I have that for the odds and the VDO for the evens. The gauge has been good, my head temperatures stay between 325-350 in everyday driving. The only time it went well below the 325 was when my carburetor was flooding out on the even bank.

I was going to put a VDO in my coupe but it is not available so I am putting in a Dakota Digital. It is the middle one of the three, in my new gauge cluster for under the radio.

I figure any gauge is a little off and use it more for trends, if all of a sudden my VDO started showing 375 or 400 it would cause me to start looking for cause after running at 325-350 for years.

maineyenko · Post by **maineyenko** » Thu Dec 01, 2016 4:40 pm

After re-reading my post, I should clarify my question, will the VDO spark plug sending units work with your digital gauge?
I'm thinking this digital gauge would work great for verifying the gauges in the dash.
How much $ do you want/need? How would you like payment?

Ken Holm

Corvair Forum