Compression issue? Parts and guide to fix

Discussion in 'Mech Tech' started by jameswick89, Mar 19, 2020.

  1. With no spark plugs in it when like this

    150 for 3
    100 for 4
    175 for 1
    175 for 2
     
  2. GARRICK CLARK

    GARRICK CLARK Sponsor

    From those figures its looking like 3 and 4 head has a compression leak at the cylinder head SEALING surfaces
     
  3. GARRICK CLARK

    GARRICK CLARK Sponsor

    There is a thin cylinder head ring on type 4's that fail
     
  4. Well looks like 3 weeks off now guess no better time to learn out to take the engine out
     
    Iain McAvoy, Lasty and Deefer66 like this.
  5. Boxes, bags and labels for the bits as they come off. I say I'll do it then get carried away and wonder where all the bits bolts nuts came from!.. photos are good reminders too

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  6. davidoft

    davidoft Sponsor

    check all valve settings to begin with( then re-check compressions) set the timing statically, will be more than good enough for a test

    check all the head bolts, if any are loose then it wants stripping to re-torque them all , have you got a dti gauge ?
     
  7. Where are you based there must be someone close that may help you.


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  8. I will have one by Wednesday.
     
  9. Is it worth getting a timing gun?
     
  10. davidoft

    davidoft Sponsor

    Yes
     

  11. So I will he cracking on with this tomorrow can I do this with the engine in
     
  12. These four are under the rocker cover.. the ones where the nuts are off and have green sealant on them.. the top 4 are under tinware..

    [​IMG]

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    jameswick89 likes this.
  13. Zed

    Zed Gradually getting grumpier

    I retorqued my heads with the engine in the bus last year. It's doable, but I would investigate any other possible cause first because just about any alternative would be easier. It's fairly pointless just doing the lower easy to get at ones, though I suppose you might learn something by finding loose nuts. However... I don't think you'd get 100psi with loose head nuts.
     
  14. GARRICK CLARK

    GARRICK CLARK Sponsor

    A loss of 75 psi over the 2 cylinders with 175 psi is a lot.
    Why don't ya seeing as its the number 4 cylinder and your about ready to drop the engine and strip it.... do this.
    Take off the number 4 rocker assembly ,remove the push rods and tubes from number 4, pull out the followers for number 4 , (put ya finger in and pull em out). Then lets see what they look like.

    Note. If the inlet or exhaust valve isn't closing properly when the number 4 is at TDC, compression escapes between the valve and the seat . This could also be why you have a low reading on that cylinder.

    Maybe the rocker adjusters are set wrong ,with a hydraulic cam there is a certain amount of turns on the adjuster screws that needs to be done from cold and with the cylinder on TDC

    On a beetle if there is a comp leak at the head you can hear it when you turn over the engine with out the coil wire attached. There is a hiss noise that comes from the bad cylinder .
     
    Last edited: Mar 24, 2020
    F_Pantos likes this.
  15. Zed

    Zed Gradually getting grumpier

    Maybe if some followers are worn and valves closing too soon, you get that unusually high pressure and the low ones are just a worn out old engine with ok valve operation?
     
  16. Zed

    Zed Gradually getting grumpier

    And if you don't actually watch the gauge as you crank, it could still have been building pressure on the low ones?
    Or
    If he did say 10 whirls each time, the ones closing the inlet sooner would build pressure more quickly?
    If it was mine and I had a workshop it would be in pieces. But so would mine if I had the space and all I want to do is look and measure for the pure hell of it.
     
    Deefer66 likes this.
  17. davidoft

    davidoft Sponsor

    I heard mention of 3 years of tax returns to be the method of assessment
     
  18. GARRICK CLARK

    GARRICK CLARK Sponsor

    Could well be Zedders
    If that's the case check the cam lobes are good by looking through the follower bores, if good.. Buy 8 new followers. Fit them ,set the adjusters properly to get the follower plungers in the right place inside the 8 new follower's and cross ya fingers.

    When i do hydraulic type 4 cam rebuilds i swap the cam and followers for a mechanical version.
    If the owner of this motor does go ed and strip it ... throw the cam as far as possible ... fit a standard flat tappet cam, Web cams are best ,but a SCAT C 25 will do.
     
    Last edited: Mar 24, 2020
    Zed likes this.
  19. First off I just want to thank every one so much you have no idea how much I appreciate all of your input, so I have access to ramps now I need to source and engine jack ideally as cheap as possible
     
  20. Zed

    Zed Gradually getting grumpier

    A lot of people do that don't they? I had a T2 with a T25 engine and box many years ago - so quiet and torquey, I really liked it...apart from the odd morning when it sounded like a machine gun for a few minutes. First time I thought it was toast until I switched off and had a google. Bliss when the noisy one pumps up though so I think overall, despite the bad rep if I had a hydraulic cam 2L I'd keep it hydraulic. It's a personal thing as much as a technical one, neither will be a racing machine.

    But...If I had to strip ANY stock engine I owned, I could not put it back together without increasing the capacity as much as possible and the hydraulic cam would go in the process so I wouldn't really ever keep one. :)
     
    Little Nellie likes this.

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