Measuring deck on built type-4

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

  1. Zed

    Zed Gradually getting grumpier

    He needed the deck for CR remember?
     
  2. Zed

    Zed Gradually getting grumpier

    Not that it actually ended up with low enough CR.
     
  3. ... your'e losing me now.. decking would up the CR by removing chamber

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    77 Westy likes this.
  4. 77 Westy

    77 Westy Supporter

    But he could never get the deck with the long cylinders. He machined the heads to retain the original push rod length and rocker geometry but compromised the combustion chamber volume.
     
    F_Pantos likes this.
  5. Zed

    Zed Gradually getting grumpier

    He had to deck it because otherwise the engine would have been 4mm too wide, pushrods too short, tins not fitting etc.

    If he shortened the barrels instead, he'd have need to increase the chambers by 20cc which is a lot.

    The heads I'll get will be using AMC 1800 castings which start life 6.5cc bigger so plus 10-12cc and accepting a slightly higher CR (but lower than it has been) is more doable.
     
    Deefer66 likes this.
  6. Zed

    Zed Gradually getting grumpier

    He had two choices.
    Find cc in head and shorten cylinders
    Deck head and leave cylinders.
    If I'd been able to find a second 1800 head, he might have done it the other way round, who knows?
     
  7. 77 Westy

    77 Westy Supporter

    That’s ^ what he should have done. You’ve ended up with a large deck and a small combustion chamber.
     
  8. Zed

    Zed Gradually getting grumpier

    I don't believe you can get the cc requirements from 1700 heads though.
     
  9. .. and I thought I struggled!..seems to get harder as you get bigger, specially when your trying to do it with what you can get hold of.. saw crank rods p&c for a 2.4 on Facebook yesterday... almost tempted...

    it's a bit of a compromise as making the chamber bigger to get volume eats away at that deck surface you're trying to keep tight..

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    Zed likes this.
  10. 77 Westy

    77 Westy Supporter

    There’s just as much meat in a 1700 head as there is in an 1800 or 2.0l to increase the chamber volume. My guess is he decked the heads because he had to machine them anyway for the 104 cylinders. He should have machined both heads and cylinders. But it’s done now and not worth arguing about.
     
    Zed likes this.
  11. I thought that too, why machine both when doing half a job is cheaper, sounds like a compromise all round :(
     
  12. docjohn

    docjohn Supporter

    Shiny metals used to be difficult to laser cut with the old CO2 machines but they are OK on the newer fibre optic lasers. In days gone by we used to get stuff like that done by wire erosion, or EDM, and I think that there are still places that do it. You can buy fully annealed copper sheet and foil, I think the grade you need is C106, in thickness down to 0.05mm. It's all just a bit of a faff though.
     
  13. Zed

    Zed Gradually getting grumpier

    I think we could reasonably guess that he either didn't fancy the job of shortening the cylinders or didn't really think it through as we're doing here.

    I do respect and gain from all the opinions positive and negative here and on Samba. You can't beat other peoples real life experiences.

    That successful experience says in order to be able to wind the torque to 30ft/lb I need seasoned Deutz diesel cylinders turned down so as not to cut into the head stud holes, pistons suitable for cutting a big dish, preferably mirroring the chamber and a copper sealing ring preferably in a groove cut into the head.

    My reality is that I won't stumble over such cylinders, wouldn't have a clue who to trust machining them. Maybe I can find some pistons suitable for dishing but it'll be a simple round dish. I'll probably not groove the head. I'll have to settle for less torque.
    Improvements...
    Less CR
    Squish deck
    Slightly thicker barrels
    Bigger exhaust valve
    More head torque
    Heads 2.5mm thicker
    Copper ring

    I'm not expecting the extra torque I'm doing now to stop the blowing but I'm interested to see what happens. Going from 23 to 27 ft lb was quite a lot tighter, more than 1/6, less than 1/4 turn.
     
  14. Zed

    Zed Gradually getting grumpier

    Thanks for the info. I was aware I could buy the sheet but hand crafting the rings would be beyond me.
    Some company somewhere will be able to supply if I look hard enough I hope, there are quite a few copper gasket makers out there. :)
     
  15. Zed

    Zed Gradually getting grumpier

    How annoying. I was all set for an 8am start, forecast dry until noon + I might have even finished the job.

    Drizzle started 8am on the dot and hasn't stopped. Even if it stopped it's too wet for my liking. :mad:

    The next good weather is several days away.
     
    F_Pantos likes this.
  16. 77 Westy

    77 Westy Supporter

    All steps in the right direction. Although if it doesn’t pink you don’t need to reduce the CR, not by much anyway.

    I wouldn’t. You’ve got to find room to fit it and I don’t see how it will prevent a leak if the head lifts. But almost all engines have head gaskets so I guess it can’t do any harm.
     
  17. Zed

    Zed Gradually getting grumpier

    Who knows? Turbo bods seem to like them too.
    I haven't bought any parts yet so I'll see if I can find better cylinders and/or dishable pistons without breaking the bank. Or perhaps some 102's, again if cheap enough.
     
    77 Westy likes this.
  18. 77 Westy

    77 Westy Supporter

    Possibly to reduce the CR?
     
  19. Zed

    Zed Gradually getting grumpier

    Apparently they help reduce shuffle which is the heart of the problem. How they would do that I have no idea.
    I could see my head/cylinder join had been shuffling.
     
    77 Westy likes this.
  20. Are they saying shuffle is a side to side movement in the plane of the surface of the head? Just trying to get my head around what shuffle means in this context...
     
    77 Westy likes this.

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