Measuring deck on built type-4

Discussion in 'Mech Tech' started by zedders, Jun 26, 2020.

  1. As I was messing about the other day looking in the spark plug holes with a cheapy endoscope...as you do...
    IPC_2020-06-25.12.53.42.2770.jpg

    ...it occurred to me that if I poked a sausage of blu tak past the combustion chamber on the compression stroke, just through TDC it would squash the blutac (blutak blu-tak?) which I could then measure for deck height..if it didn't end in tears of course. I could oil the blutack to stop it getting stuck to the head or piston.

    What do you think?
     
    Last edited: Jun 26, 2020
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  2. davidoft

    davidoft Sponsor

    You could try using some plastiguage then you could pull it back out , we used to put solder in to check deck height but then pull the head back off obviously:eek:

    but blue tac should work , attach string to the blue tac to pull it back out, could also wind the valve clearances right down to keep one open for pulling out ness :)
     
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  3. its possible but not without its risks, A long oiled sauage may do the trick as long as it didnt seperate or get stuck. I need to consult my gynecology certificate
     
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  4. What sausage would one use :D
     
  5. Dubs

    Dubs Sponsor

    Not German ones, they are the Wurst.
     
  6. Dubs

    Dubs Sponsor

    If you squash blu tac, does it not expand a bit when you let go?
     
  7. I'll check. It's very old blue tack which may work in its favour.

    Luckily it's raining so I haven't done anything rash yet.
     
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  8. davidoft

    davidoft Sponsor

    :D :D
     
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  9. Dubs

    Dubs Sponsor

    If it works, I will be trying it on my engine, as I was far to lazy / shoddy to do it at the building stage.. :thumbsup:
     
  10. If that's type-1, the plug angle isn't so suitable I think. Type-4 aims at exactly where I need to insert my straight sausage. You'd need a bent sausage for type-1.

    I still won't know the head cc. If you are equipped and have a stock 1700 head lying around that would be helpful as a base point.
     
  11. Solder and a micrometer is the accepted method of measuring the squish band on a 2 stroke , which is in essence what you're trying to achieve.
    I'm not saying it won't work with a 4 stroke but there's a totally different set of problems with a 4 stroke such as dished pistons and a different head profile although I would think there'll be a thin band around the top edge which should be measurable . You will of course need a base line (stock ?) Measurement to start with , IF the heads haven't been reworked ...
    For a true deck height and volume reading the engine has to come out - but you know that already ....


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    Last edited: Jun 26, 2020
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  12. Dubs

    Dubs Sponsor

    Mines a 1700 car engine with domed high compression pistons (w code )

    I don't have any other type 4 heads at hand unfortunately.
     
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  13. If it's in a car and the CR went up a bit it wouldn't matter too much, might even be good!
     
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  14. I'd worry that solder once squished wouldn't come back ot of the plug hole but I guess I could make a solder sausage a little wider than the expected mahoosive 3.5mm deck. I have micrometers. :thumbsup:
    Yes of course cc will still be the missing part of the puzzle, but I have a photo of the head with one chamber original and one made bigger. Can't find info on stock cc though. I'm sure if I measure the deck and estimate the cc I'll at the least know if it's a mile out.

    You can imagine that with flat top pistons I have a big shelf to aim at opposite the spark plug hole...
    IMG_20151121_121311430_zpsa5ecnfms.jpg
     
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  15. On my Yanmar 330cc single cylinder boat diesel they suggest annealed copper wire. Because if you use flux cored solder it may disintegrate I suppose.

    But the squish zone on that is almost 100% of the head area and the gap is about 0.7mm...because there is a secondary combustion chamber which is a few cc which you remove to poke the annealed wire in through.


    I think the problem around 3.5 mm deck height is that the wire is so thick it gets hard to squash.
    Also you may have problems with the piston rocking rather than squashing the wire over one side. The boat diesel combustion chamber is about central on the piston.
     
  16. 3.5mm deck.. I can hear Samba tutting from here..

    Do you know how much was skimmed off the face to know how much chamber you lost from stock..if a stock volume turns up

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  17. I’d think Blutack would end in tears.

    Solder sounds a better idea. At least you can keep a hold of it.
     
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  18. German sausage of coarse .
     
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  19. Here's another picture, I'd say as little as possible, he knew he was up against it CR -wise. You can still tell where the 1700 barrel sat?
    IMG_20151110_153857975_zpsyantexxf.jpg
     
  20. Gap measuring.. would something like "Thermoworx Polymorph" plastic work? Heat granules up in a cup of boiling water, make a sausage as it cools.. squash in the chamber and leave to set?

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