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Head temp on #2 says I am hotter than the rest.
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storm
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PostPosted: Thu Apr 08, 2021 4:02 pm    Post subject: Head temp on #2 says I am hotter than the rest. Reply with quote

Having a issue with head temp on #2 on a summer day of 85 degrees.Moved sensor under spark plug to other cylinders and they say 280~310 degrees. Number 2 says 350-400. Check if anything obstructing air flow? Nothing. IDF carb on that side is jetted the same as the other side carb. One thing that surprised me was I had the bus out for a short ride around Xmas, air temp was 25 degrees. The drive was 3 miles. The head temp gauge on number 2 said 350 degrees. Something is wrong here. Oil temp on that cold day was 150. Any thoughts. G
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PostPosted: Thu Apr 08, 2021 5:19 pm    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

storm wrote:
Having a issue with head temp on #2 on a summer day of 85 degrees.Moved sensor under spark plug to other cylinders and they say 280~310 degrees. Number 2 says 350-400. Check if anything obstructing air flow? Nothing. IDF carb on that side is jetted the same as the other side carb. One thing that surprised me was I had the bus out for a short ride around Xmas, air temp was 25 degrees. The drive was 3 miles. The head temp gauge on number 2 said 350 degrees. Something is wrong here. Oil temp on that cold day was 150. Any thoughts. G


I'm bookmarking this in case you figure it out! Laughing
I have a type 1 with a 1776cc, dual 40IDF's, CHT sensor under all four plugs. 3 and 4 seem to be ok, with 3 consistently 20-30F hotter than 4.... 1 is normally somewhere between those two, I think because it is picking up residual heat from 2.. 2 is almost always 50-90F hotter than 3.

Car runs great though and no other problems, so i'm just keeping an eye on it.. my hottest temp with bad jetting and a little out of tune was maybe 360F though..

I just messed with my sync, jetting and adj screws last week though and dropped my average temps by at least 50F..
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PostPosted: Thu Apr 08, 2021 8:45 pm    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

Does #2 have a Heli coil ? Are the threads good and the plug sealing surface? Valves adjusted? Compression good? Have you done a leak down check? Lots of reasons one cylinder can be off.
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PostPosted: Thu Apr 08, 2021 8:49 pm    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

How's it running?
My usual fix is to not use a CHT gauge. They make me paranoid. Very Happy
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storm
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PostPosted: Fri Apr 09, 2021 7:44 am    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

G is back, thanks for responding. The engine rus fine and strong no pining, back firing, popping, 2027 cc Scat kit, only less than 3500 miles. New 40x35 heads. Thermostat and flaps. I live in an area of hills, some are 10% inclined for 3/4 mile. Ok on that hill 3 gear going up head temp on #2 400 degrees, Going down the head cools down to 350 degrees. I know other Vw people, there temps are even higher than 400 degrees. Also thinking to use a inforred temp to verify temp. Guess I just keep an eye on it and not get paranoid as Culito says. Basirhead I live not to far from you will shoot you an pm.
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mondshine
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PostPosted: Fri Apr 09, 2021 5:48 pm    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

This might be a little bit "out of left field" but I have seen the sealing washers on spark plugs distort the thermocouple ring terminals to the point that allows tiny combustion leaks causing erroneous CHT readings.

Substituting copper shim washers (I used 1/2" ID x .01 thick for my 12mm plugs) for the regular crush type spark plug sealing washers keeps the thermocouple ring terminals flat and sealed against the head.

I get them from McMaster.

Just a thought...
Good luck, Mondshine
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raygreenwood
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PostPosted: Fri Apr 09, 2021 7:24 pm    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

mondshine wrote:
This might be a little bit "out of left field" but I have seen the sealing washers on spark plugs distort the thermocouple ring terminals to the point that allows tiny combustion leaks causing erroneous CHT readings.

Substituting copper shim washers (I used 1/2" ID x .01 thick for my 12mm plugs) for the regular crush type spark plug sealing washers keeps the thermocouple ring terminals flat and sealed against the head.

I get them from McMaster.

Just a thought...
Good luck, Mondshine



Yes.

I HATE the standard CHT plug washer connection.

The risk is NOT that the tiny weld bead of the thermocouple will not be held flat. It really does not matter....if you look at enough ring type TC's. I have seen quite a few on engines and we use hundreds of them all over the place in my industry.

They come in two varieties...of crimping.

1. The small TC weld bead is at the very end of the crimp barrel toward the inside right next to the spark plug body...open to air but in contact with the copper. This works fine but depending n how good the fitting is while they are crimping....the bead can actually be out of contact from the copper crimp ring and be up in the air by about .020". This can cause some fluctuations in readings with a lot of airflow.

2. The bead...is properly ...just inside of the crimp barrel roll....fully enclosed by metal...but very close to the inner end...as close as possible to the spark plug barrel.

The risk with this type of crimping is if the barrel was squeezed way too hard during crimping and it can actually crack the TC weld bead. This causes...some strangeness in readings...and eventually it goes dead.


The risk...with this whole system....is just what you said. Spark plug gas leaks through the threads.....can cause out of whack high readings.

I finished a new version of something I did about 20 years ago...but just have not had time to post the "how to".

A preview picture or two:

Here is the gist...its a crimp on ring terminal that fits AROUND the sparkplug to allow using the stock plug gasket and allowing changing and removing spark plugs without worrying about the ring terminal or sealing.

Image may have been reduced in size. Click image to view fullscreen.


But...you have to enlarge the well around the spark plugs from about 0.875" stock to right at 1.0". So you enlarge exactly 1/8"....1/16" on each side of the plug. A machine shop can do this in a jiffy...I did it with a dremel and a flat plate in the bottom to protect the spark plug thread.

And....the crimp ring is held in by a snap ring:

Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


Here it is after crimping but before soldering. Soldering is done so that there is no risk created by having to crimp the bead inside of the barrel and cracking it...and to allow very tight and heat conductive contact to the ring terminal...and allow the TC bead to be as close to the plug without touching it as possible.

Image may have been reduced in size. Click image to view fullscreen.



After soldering. Yes....this is special 500+ degree solder. If it melts off during running...please come to a stop and put out the fire in your engine. Very Happy

Image may have been reduced in size. Click image to view fullscreen.



This is after shaping the solder bead to fit smoothly between the snap ring loops....and coating the whole thing with a high temp circuit board varnish. It does not block heat conduction. It enhances it.

Image may have been reduced in size. Click image to view fullscreen.


In the head for a test fit.

Image may have been reduced in size. Click image to view fullscreen.



Testing in an oven alongside a normal CHT ring that replaces the spark plug gasket shows a variance between two matched TC's.....of less than 1.5*.

Still working on those pictures for the how to.

Another option I have made...many years ago....when I first did this...works really well. Its a solid aluminum crimp ring that is simply press/shrink fit...but I have to make a new one to show how it works in pictures.

Ray
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orwell84
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PostPosted: Fri Apr 09, 2021 7:47 pm    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

I would try to first try to rule out if there are any differences in the way the sensor is installed in #2 that may affect the readings before assuming it’s an actual difference in the temps of the cylinder heads. I would suspect the readings first.
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PostPosted: Fri Apr 09, 2021 7:53 pm    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

Interesting idea Ray.
Something to consider for next time the engine is out.

For now, the copper shim washer is working for me.
I was pleased to see that a single washer did not cause the thermocouple ring terminal to turn/twist as the spark plug was torqued.
I had considered using two .005 thick washers to prevent this, but the single .010 washer worked well.

So for now, I will employ the LITFA rule.
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PostPosted: Sat Apr 10, 2021 11:32 am    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

Wow!, Storm here. I think now that the 12 mm 3/4 reach spark plug without the gasket is doing something. I did test in hot water it’s function - it was off 20 degrees higher than 212 degrees. These sensors (have 2) are from Spruce aircraft supply. As with the motor itself in good shape valves with steel pushrods are .002 clearance. Runs strong and idles at 750rpm smooth. Ray, I like your ideal of using the ring on the head independently of the spark plug. To do this modification the engine would have to come out. The snap ring to hold the copper washer to the head.would have to be machine. I have cutting tools for head work. Before I would practice on an old head first. Then decide if I want to do the work on this engine. I my experience with Vw engines if working good don’t take apart. There is always something goes wrong and it does not run like it did before. For now, I will use a infulred temp meter to verify temp readings. Pardon my spelling. 350 degrees on a short ride in 25 degree weather does not seem right. Thanks a lot.
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PostPosted: Sat Apr 10, 2021 2:26 pm    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

First things first. Verify that all the sensors read the same in boiling water. Maybe you have already done this. If not, swap the coldest sensor with the hottest sensor and see if the higher temp follows the sensor. May not be the engine at all.
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PostPosted: Sat Apr 10, 2021 2:40 pm    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

storm wrote:
Wow!, Storm here. I think now that the 12 mm 3/4 reach spark plug without the gasket is doing something. I did test in hot water it’s function - it was off 20 degrees higher than 212 degrees. These sensors (have 2) are from Spruce aircraft supply. As with the motor itself in good shape valves with steel pushrods are .002 clearance. Runs strong and idles at 750rpm smooth. Ray, I like your ideal of using the ring on the head independently of the spark plug. To do this modification the engine would have to come out. The snap ring to hold the copper washer to the head.would have to be machine. I have cutting tools for head work. Before I would practice on an old head first. Then decide if I want to do the work on this engine. I my experience with Vw engines if working good don’t take apart. There is always something goes wrong and it does not run like it did before. For now, I will use a infulred temp meter to verify temp readings. Pardon my spelling. 350 degrees on a short ride in 25 degree weather does not seem right. Thanks a lot.



The snap ring and copper connector ....works well. I did all of the machine" work"...carefully with dremel sanding drums, a telescopic gauge and a special dremel high speed cutter ($5) I modified to make a slot for the snap ring.

And yes...this is an older but good head. I was mapping this out because I am about to install one on a set of 1.8L heads I and getting ready for an engine build I have been working on.

BUT....wait a week until I post the whole thread along with the aluminum version of this.

The aluminum part....works just as well if not better...and does not require a snap ring....and could be made to not need nearly as much expansion of the well around the spark plug.....if any at all.

The original aluminum ring I made back in teh early 2000's...was simply made from a cheap piece of aluminum plate I bought at home depot.

Because you can use 1/4" thick aluminum plate...the ring can be thinner in ID and OD.....and if you have a machine shop precision expand the counter bore....you can adjust the aluminum ring OD.....to simply press in or shrink in. Once it is in it will not come out unless you pry it out.

I no longer have the original one I made because that set of heads got destroyed and I forgot to pull the ring out.

Making a slick accurate hole in either .030" copper plate or 1/8" or 1/4" aluminum plate is really simple....with this tool....

https://www.toolnut.com/bosch-htw34-3-4-thin-wall-hole-saw.html

These are super thin wall, super sharp and very accurate.

Ray

Ray
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PostPosted: Sat Apr 10, 2021 6:07 pm    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

https://au.omega.com/pptst/WT.html

I use these , one on each cylinder . I did not want to drill and tap a mounting hole in case it caused a stress point and crack later , so to mount them , I wedge the plate against the plug boss so the plate is hard against the head , then use 24 hour JB weld to cover the plate and glue the plate to the head , The JB weld also insulates the sensor from the cooling air flow of the fan .

So far I've 2 engines done this way and never had one fall off in years of use .
I also use long leads ,so the cold junction to the gauge (MGL TC-1) is in the cabin , under the back seat . It's important the cold junction is at the same temperature as the gauge .

Something to try , is using heat soak to verify odd readings . after the run , turn the engine off and check the reading in 5 minutes . If it is a lot hotter than #1 , then it will drop temp quickly , spreading the temp over the whole head . Visavursa for #1 , it will increase in temperature when turned off .
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PostPosted: Sat Apr 10, 2021 6:45 pm    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

Just as a reference, my thermocouple is a "type J".

This table shows output in millivolts.

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PostPosted: Sat Apr 10, 2021 8:28 pm    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

Wreck wrote:
https://au.omega.com/pptst/WT.html

I use these , one on each cylinder . I did not want to drill and tap a mounting hole in case it caused a stress point and crack later , so to mount them , I wedge the plate against the plug boss so the plate is hard against the head , then use 24 hour JB weld to cover the plate and glue the plate to the head , The JB weld also insulates the sensor from the cooling air flow of the fan .

So far I've 2 engines done this way and never had one fall off in years of use .


Yes...pretty much a version of what I am doing. You just need whatever the TC is crimped or soldered to... hard and tight against the head as close to the spark plug as possible. Ray
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PostPosted: Sun Apr 11, 2021 6:23 am    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

You are running dual IDFs correct?

Perhaps your mixture screw on cylinder #2 needs adjustment
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PostPosted: Sun Apr 11, 2021 9:48 am    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

Swap the idle jet to another cylinder and see if the increased temp goes with it. I’ve seen as much as a 10% variance in flow on idle jets. The 50/55/60 sizes tend to be better. The single steps can be all over the place.
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PostPosted: Sun Apr 11, 2021 10:23 am    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

Texoval, yes duel IDFs mixture adjusted best lean, then 1/4 open more. . Now with many responses on this thread, I am sorta convinced that my engine is working OK in#2 head chamber. The problem is not getting a true temperature reading. Compared to the other 1,3,4, head chambers that showed lower temps. Ok, #1 head temp is a little higher than 3&4. Does it get higher because it is getting temperature transferring from #2?. I have these sensors on all of the four spark plugs with out the crush washer. Maybe #2 sensor is toast. Also maybe switch a known sensor from another spark plug to compare readings. I like Ray’s idea of making a sensor platform next to the spark plug. G.
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PostPosted: Sun Apr 11, 2021 11:35 am    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

storm wrote:
Texoval, yes duel IDFs mixture adjusted best lean, then 1/4 open more. . Now with many responses on this thread, I am sorta convinced that my engine is working OK in#2 head chamber. The problem is not getting a true temperature reading. Compared to the other 1,3,4, head chambers that showed lower temps. Ok, #1 head temp is a little higher than 3&4. Does it get higher because it is getting temperature transferring from #2?. I have these sensors on all of the four spark plugs with out the crush washer. Maybe #2 sensor is toast. Also maybe switch a known sensor from another spark plug to compare readings. I like Ray’s idea of making a sensor platform next to the spark plug. G.


A couple of notes. What engine platform is this....type 1 or type 4?

There are some notable real world differences in cylinder head temp on type 4 due to imbalances in the cooling system flow is the only reason I ask.

The other problem I see with the standard method of using the thermocouple connector as the actual sealing washer of the spark plug......is that if you have ever taken a spark plug and either connected it to a distributor oin a bench or put it in a coil tester.....and fired it for about 5-10 straight......the spark plug if its just in a ground clamp with be about 250° or more in a very short space of time. If you have it bolted into a chunk of metal.....its considerably less hot because its conducting some of its heat into the metal. As soon as the metal ground block gets heat saturated .....the sparkplug will get very hot. Any electrode will.

So.....even though the idea of putting the CHT at the sparkplug point is because thats where the flame starts....and it should be the hottest point of the head......you dont really want a fair portion of your measured temperature to be aftually coming from the spark plug ITSELF.

You "could" be getting elevated temp readings just from a spark plug that has excessive resistance....or from a sprakplug whose wire has less resistance or whose rotor or cap gap has less resistance.....or from a spark plug that has a heat transfer issue like a thread insert (which someone already mentioned).....or has excessive anti-sieze, grease or lube.....which not only can block heat transfer but can create higher resistance to ground......and higher resistance to arc.....which means higher heat.

The issue is one of the prime reasons ....along with tbe plug sealing issues....and issues with getting plugs in and out and not fouling the TC contact.....that I wanted to seperate the TC point of thermal contact to about 1mm away from the plug itself. Ray
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PostPosted: Sun Apr 11, 2021 12:37 pm    Post subject: Re: Head temp on #2 says I am hotter than the rest. Reply with quote

storm wrote:
Texoval, yes duel IDFs mixture adjusted best lean, then 1/4 open more. . Now with many responses on this thread, I am sorta convinced that my engine is working OK in#2 head chamber. The problem is not getting a true temperature reading. Compared to the other 1,3,4, head chambers that showed lower temps. Ok, #1 head temp is a little higher than 3&4. Does it get higher because it is getting temperature transferring from #2?. I have these sensors on all of the four spark plugs with out the crush washer. Maybe #2 sensor is toast. Also maybe switch a known sensor from another spark plug to compare readings. I like Ray’s idea of making a sensor platform next to the spark plug. G.


Funny, I am having the EXACT readings... #2 is hotter than 3, and #1 is slightly hotter than 4...

I came to the same conclusion, that 3 and 4 are running in the correct range, 2 is running hot and residual heat is affecting the reading on 1.

Like i said at the beginning, I've been unable to figure out why 2 is running hot.. but I haven't seen any negative effects yet.. Confused
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