Cylinder Head Temperature Gauge - Should I? & or Air Fuel Ratio

Discussion in 'Mech Tech' started by paulcalf, Jul 7, 2021.

  1. Should I install a Cylinder Head Temp gauge, if so recommendations please
    & or re connect my old Air Fuel Ratio Gauge?


    Background :
    At Techenders Dr Mike @mikedjames diagnosed I had very low compression on Number 2 Cylinder.

    Later the engine came out & heads got removed, showing an exhaust guide on number 2 had moved 'up'.

    1st photo shows brass valve guide 'up' on number 2 exhaust.

    [​IMG]


    Cylinders 3&4 had ok compression, but on removal of that head both exhaust guides had moved up!

    2nd photo shows both exhaust guides up on cylinders 3&4

    [​IMG]


    Took both heads to a VW machine shop who discovered:
    7 out of the 8 valve guides were loose and the other one tapped out easily.
    Intake valve seat on number 2 had come loose, but luckily hadn't done any damage.

    There were no visual signs of the heads overheating , the spark plugs all looked ok not showing they had been lean or rich etc etc. Some photos of the valves and spark plugs on each cylinder at end of the post.

    Heads have only done 21K miles since new.
    Mofoco 042 heads with 40x35.5 valves.
    Type 1 engine .2110cc.
    Oil changed every 3000 miles or less.
    Valves checked and adjusted at the same times.
    Oil temp has never seemed high.
    Engine has been rolling rd 2/3 times.
    Old CB Air Fuel Ratio Gauge hasn't been used since I changed exhaust and on the old exhaust it used to just show 'rich' when accelerating and then swing back to 'normal'.


    The heads could have overheated.
    The valve guides may not have been fitted 'tight' enough in the first place.

    I don't want this to happen again as I can't just whip an engine out, so it has cost me money and time not able to use the bus/go camping.


    Should I fit CHT gauges or is it more hassle than its worth?
    If i'm doing it i'd like to see the temp on all four cylinders otherwise its bound to be a different cylinder with the issue.
    Or is fitting a CHT gauge an over reaction - It's bound to be something different that causes me grief next time!
    I'd use the CHT to show me if something had changed from the 'norm'.
    A quick search showed Jake Raby saying: If the thermocouple goes anywhere excpet under the spark plug, you may as well not even have the gauge...


    Machine shop said he thought an Air Fuel Ratio gauge would be more use.
    So I could get a new 02 sensor fitted into my exhaust, but last time the gauge didn't show me much!

    Your thoughts, experiences and product recommendations are welcomed!

    Sorry it's so long, but hopefully it provides enough info.

    Cheers

    Paul

    [​IMG][​IMG]

    [​IMG][​IMG]
     
    Last edited: Jul 7, 2021
  2. No. Just drive your van ;).
     
    Lasty, matty and Barry Haynes like this.
  3. well that is what i had been doing, quite happily until recently!
     
  4. Sounds suspicious to me, why did all the guides work loose and yet there's no obvious overheating signs?

    As far as outcomes go, Paul, this actually doesn't seem too bad. If only we knew how the guides had worked loose?

    PS good job you didn't need to rely on my offer of help to get your engine out in the end. I can't even drive at the moment, thanks to a badly sprained wrist :(
     
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  5. I've been out of the loop for a long time and hadn't heard of Mofoco heads. What sort of reputation do they have? Maybe the cause of your problem was just that they're marmite to start with? I honestly don't know, maybe they're considered the dogs do dads?

    I recently fitted a CHT gauge to mine which was fairly straightforward but the readings are not necessarily absolute and have to be taken in context depending on the set-up you end up with.
     
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  6. I agree. Sensors help us to continue doing what we love best; keep the van on the road so we can drive it.

    The only "sensors" I have are a temperature gauge which is intalled at the taco plate (which helped me identify an overheating problem before it got too bad), and a fuel pressure gauge (which helped me diagnose an issue with a failing fuel shut off solenoid).

    I would like to add oil pressure gauge, and perhaps CHT for each Cylinder.....so follolwing this post with interest.

    Have you seen the "food temperature" CHT setup someone else did on this forum recently?
     
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  7. How the valves worked loose is the million dollar question.
    It is strange.
    The Machine shop said he had seen loose guides on heads made by all of the top players!
    He thought that many companies didn't fit them in tight enough.

    No way of knowing how mine came loose at the moment.
    I'm waiting to hear back from Mofoco.
    I have the internal bore measurements and the valve guide measurments, so i may be able to find out if they have changed from what they should have been from the factory!

    Hope your wrist recovers soon.
     
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  8. What CHT gauge did you fit please?
    They were the heads chosen by my engine builder, who has fitted lots of them and i've read good things about them.
    They drove great and i didn't even realise there was a problem until no compression was diagnoosed on cylinder number 2 (i'm guessing that when the engine had warmed up the loose seat moved back into position and then i was driving on all 4 cylinders?)

    https://www.mofoco.com/item/MOFOCO_042_BIG_VALVE_CYLINDER_HEAD_CCH042/235/c52

    This is how they are described on Dan Simpsoons website:
    http://www.dansimpsonvwengines.com/product/mofoco-042-street-cylinder-heads-pair/
    Mofoco 042 Performance Cylinder Heads are not a production line head. Once the castings arrive at Mofoco, they are part CNC and part hand machined the team at Mofoco. The machinist, Dan, lives and breath’s performance engines and machining. Years of dedication and passion go into this process and he personally installs all the seats and guides by hand affording the correct press fit. Unlike similar fitted on a production line using mechanical press. This guarantees neither will move or come loose, even under the hardest abuse. All 3 angle cuts on all the seats are also carried out by hand. Finally every head is vacuum tested on completion. Before final assembly, he lubes all the valve stems, sets the springs to the correct installed height, then fits the retainers and collets.
     
  9. Million Dollar question, indeed.

    Be very interesting to hear what they have to say. The good news is, however, that the heads can be saved.

    Thanks, not being able to drive is a bit of bummer :(

    It's quite a laugh watching me trying to take my t-shirt off one handed :oops:
     
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  10. For years i've had a dispstick oil temp gauge and an oil pressure gauge (but they don't show what is happening temp wise in the heads)
     
    jim mcglynn likes this.
  11. I had a lucky eBay score with my CHT gauge and picked up a NOS Westach light aircraft kit from the late '70s for £50. I had to modify the single thermocouple ring from an 18 to 14mm which I currently have fitted under #4 plug for ease of access/installation. I believe the plug type sensors give a more realistic reading. I've managed to site the cold junction inside the van in the spare wheel well which should help with accuracy (AFAIR, mine's calibrated with the cold junction at 70*f) but more modern set ups may be able to compensate for cold junction temps? There are many people with more knowledge of thermocouples than me on here.
    [​IMG]

    [​IMG]

    The pitch for those heads sound impressive. Guess you need to be talking to your engine builder and/or Mr Simpson?
     
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  12. Thanks that is useful info, ill set up an ebay alert and see what i can find.

    I've spoken to the engine builder when i knew some valve guides had moved, he said it didn't seem right for so few miles.

    He suggested i speak to the head manufacturers as well.
    Engine builder is now on holiday so i haven't updated him with the fact that 7 out of 8 guides were loose!

    Mr Simpson is unfortunately no longer with us (RIP), that was info from his website, he was another supplier of Mofoco heads.
     
  13. Nice one Jim

    I've found and replied on the bbq temp gauge thread.

    Perhaps i should just gaffer tape a few of those to the outside of the cylinders! :)
     
  14. I’d be changing out valve seats and new valves
     
    paulcalf likes this.
  15. theBusmonkey

    theBusmonkey Sponsor

    Wow, bad and good news I guess Paul. Caught it all in time.
    I know next to nothing about the type 1 but we have had a cht sender and gauge fitted to the type 4 for the last 13 years.
    FWIW and maybe this helps, on a type 4 it's recommended to have under 3 plug because that's the one that conventionally runs hottest.
    However, the gauge is only a tell tale. As you rightly point out, it won't let us know if No1 valve is bashing its way into the head...again. or if number 2 piston has a hole in it. I can't imagine it's hugely accurate, but what it does do is indicate anything out of the ordinary...but that also depends on load, ambient, gradient etc etc..
    I wonder if it's worth asking Dr Mike to knock something up for you if you are really concerned:thinking:
    On the flip side, they aren't dubbed worry gauges for nothing. Your Jedi force and feeling whilst driving, plug inspections when you do the oil every 3k and compression test every now and then will probably tell you just as much...
     
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  16. I've gone with what the machine shop have said, which i think is re cuting all valves and seats.

    Replacing the dodgy seat and all guides
     
  17. Thanks. That is will help my thinking and decision
     
    theBusmonkey likes this.
  18. Was your last AFR Wide or Narrowband?
    Wideband is more informative and more expensive (but will pay for itself over a lifetime by saving you expenses by keeping the engine well tuned).

    CHT don’t have to be expensive. Mine aren’t classically pretty though. Nor Exhaust Gas Temperature, which is also useful. £100 for both. The one I linked to earlier is Cold Junction Compensated (whatever that actually means).


    Sent from my iPhone using Tapatalk
     
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  19. I can't remember if it was wide or narrowband, just that it was a 3 wire 02 sensor.

    Edit it was a 3 wire oxygen sensor zirconia type. It cost 20quid. So narrowband more than likely.


    I'm trying to source something suitable that will work with the Afr gauge.

    The CHT sensor you suggested seems good, ideally I'd like 4 cylinder readings into one gauge.

    [​IMG]
     
    Last edited: Jul 7, 2021
    Zed likes this.
  20. I have the Innovate wideband set up with digital gauge …it’s brilliant
     
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