Results 1 to 15 of 15

Thread: Lapping in new valves

  1. #1
    Forum User
    Join Date
    Nov 2010
    Posts
    34
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Default Lapping in new valves

    Soooo i took the missus car out thursday morning and came home on one of these.



    Problem being a snapped cambelt.(New belt and tensioners replaced in september btw)

    Anyway heres the outcome of that!








    Anyway i decided rather than get a used head(£350) i would rebuild this one so i bought new valves,top end gasket kit,stretch bolts etc.

    The guides are all fine so thats all good.

    Its a long time since i lapped new valves in (last car was a 350 small block chevy) now i tend to use a drill attachment with a rubber hose on the stem end and ive so far done 2 exhaust and 2 inlet.

    Im just wondering if the new valves are stupidly hardened?As ive read plently of conflicting advice on the tinterweb about how long to grind them in on vw's?
    I know the principal behind it and ive got a decent 1mm grey line on all 4 valves by lapping them 10 mins with course and 15 mins with fine but just wondered if anyone had any experience lapping in NEW vw valves?

    Car is a 1.6 16v AZD lump.

    ....and no she wont let me put a 1.8t in it :drool:

  2. #2
    Forum User
    Join Date
    Dec 2007
    Location
    ~ MOT TESTING ~ plymouth
    Posts
    681
    Thanks
    13
    Thanked 12 Times in 10 Posts

    Default

    i would drop the pistons and check for any pinched rings,
    if its got wheels or boobs,,,sooner or later its gonna cost ya !!!

  3. #3
    Forum User
    Join Date
    Nov 2010
    Posts
    34
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Default

    Quote Originally Posted by tones61 View Post
    i would drop the pistons and check for any pinched rings,
    Thats not something ive come across before.Would you mind explaining please.

  4. #4
    Forum User
    Join Date
    Nov 2010
    Posts
    34
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Default

    If its anything to go by the bores are perfect and ive filled them up with petrol to check for leakage and there is none.

  5. #5
    Forum User
    Join Date
    Dec 2007
    Location
    ~ MOT TESTING ~ plymouth
    Posts
    681
    Thanks
    13
    Thanked 12 Times in 10 Posts

    Default

    the rings can get trapped between ring lands due to valves hitting pistons,
    if its got wheels or boobs,,,sooner or later its gonna cost ya !!!

  6. #6
    Forum User
    Join Date
    Nov 2010
    Posts
    34
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Default

    Ah ok i see.But surely if the bore isnt marked in anyway this would indicate they are ok?As a pinched ring would expand a little causing a score/scratch on the cylinder bore wall?
    I dont really want to pull the pistons out as i hate taking the sump off this thing, but i will if i have too.

  7. #7
    Forum User
    Join Date
    Dec 2007
    Location
    ~ MOT TESTING ~ plymouth
    Posts
    681
    Thanks
    13
    Thanked 12 Times in 10 Posts

    Default

    ok dude,its a gamble while the head is off,'if' a ring is stuck it'll smoke later on,
    if its got wheels or boobs,,,sooner or later its gonna cost ya !!!

  8. #8
    Forum User
    Join Date
    Nov 2010
    Posts
    34
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Default

    Im not doubting your advice in anyway and for the sake of another 3 hours it will be worth doing but im just interested in the mechanics of it all.
    How does this happen by the valve hitting the piston?Does the shock of the collision make the ring jump landings?

  9. #9
    Forum User
    Join Date
    Dec 2007
    Location
    ~ MOT TESTING ~ plymouth
    Posts
    681
    Thanks
    13
    Thanked 12 Times in 10 Posts

    Default

    aye,no probs,the valve hitting the alloy piston can squash the alloy down onto the ring lands hences trapping them,had it a few times on engines in the workshop,
    if its got wheels or boobs,,,sooner or later its gonna cost ya !!!

  10. #10
    Banned after significant club disruption Dec 5th 2014 Chris Eyre's Avatar
    Join Date
    Oct 2003
    Posts
    43,685
    Thanks
    247
    Thanked 395 Times in 228 Posts

    Default

    Here's a thread from a while back which may help:

    http://www.clubgti.com/forum/showthread.php?t=37905

  11. #11
    Forum User
    Join Date
    Nov 2010
    Posts
    34
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Default

    Aaaah i get you now.Great stuff thanks for explaining.I will whip them out after the weekend shift.

    Do you have any ideas on the lapping of new valves in an old head?Some people say do,some say dont.Personally i think its better too but ive not done any major rebuild work on newer vws.Essentially they should be the same as any engine but im just anal and want to cover every angle.

  12. #12
    Forum User
    Join Date
    Nov 2010
    Posts
    34
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Default

    Quote Originally Posted by tones61 View Post
    ok dude,its a gamble while the head is off,'if' a ring is stuck it'll smoke later on,
    Fantastic Chris thanks mate,That will help nicely

  13. #13
    Forum User
    Join Date
    Oct 2003
    Location
    United Kingdom
    Posts
    584
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Default

    You don't really need to lap them in, new valves don't get lapped into new heads at the factory. But its a good way of highlighting/getting rid of any damage to an old seat.

    What i'm surprised that no one has mentioned is to make 300% sure you get rid of every trace of the paste. Leave some in and you will have been far better off not lapping at all.

    Mike

  14. #14
    CGTI Regional Host Dan W's Avatar
    Join Date
    Jan 2009
    Location
    Penryn, Cornwall
    Posts
    3,733
    Thanks
    15
    Thanked 114 Times in 79 Posts

    Default

    The big question is why did the belt snap if it was all only changed in September? Something must be wrong and/or the belt was fitted incorrectly. Did the water pump get changed also? I'd be doing a thorough investigation in case it happens again in a few months!

  15. #15
    Forum User
    Join Date
    Nov 2010
    Posts
    34
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Default

    Ive got a parts washer in my garage so it will be getting a good rinse after the grinding.
    Ive done 4 now so will carry on to keep the others the same.

    As for the reason it snapped,im stumped!
    When i bought it i put new hyd lifters,roller rockers,oil pump full cambelt kit etc Did it all myself as ive done plenty of cambelts in my time.
    Its difficult to get it wrong as all 3 tensioners have the preload needle markers you have to set them too and i know they were cock on.

    When i stripped it all down this time round i checked all tensioners and they were fine.The waterpump was perfect but i have changed it again anyway.
    The engine turns over perfect with no noise.
    There is no play in anything in the block at all either!

    It was a goodyear belt/kit bought from ECP so ive emailed them to see if they have had any problems with a paticular batch after giving them the batch code off the belt.

    Dreading running it up for the 1st time.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •