1.8 GU engine cam upgrade head scratcher

Discussion in '8-valve' started by Andrew Lewin, Jul 4, 2020.

  1. Andrew Lewin Paid Member Paid Member

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    Hi all. Long time lurker, first time poster here as i'm very confused and Google is getting me nowhere.

    Got a 1990 (G) Mk2 with a GU engine that I attempted to fit a GTI cam to today.

    Upon fitting the cam, I was in the process of giving the engine a couple of test rotations to check I hadn't ballsed anything up and to my horror, stuck solid!

    After carefully removing the new cam I tentatively refitted the old one and fully reassembled everything. Engine turned over first time and all seems well.


    I can't for the life of me figure out what went wrong. The cam I purchased (ebay) was listed as coming from a MK2 GTI and has a large "G" at the sprocket end. I know that I need a hydro cam (my car being a post '87 model) and I thought I'd purchased the right cam. Clearly not.

    Any help would be very much appreciated.

    Many thanks in advance, Andrew.
     
  2. Jon Olds Forum Junkie

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    Most 8V heads have chambers in, meaning the valves are recessed into the head, away from the pistons.
    You would have to be a long way out to get into clash trouble.
    Some race cams have so much lift the lobes hit the head casting, unlikely to be the fault.
    A cam bearing back to front would sieze the cam. ho hum, we are all human.
    Always go back to basics;
    plugs out, get the crank so all pistons are at the same height (midway)
    cam belt off
    rotate cam 360 degrees
    rocker cover off, get no1 cylinder so the lobes are as far away from the valves as possible
    symmetrically
    rotate the pistons until no is at the top
    refit belt
    rotate slowly with spanner on crank pulley, never starter motor
    should be somewhere near now
    Jon
     
  3. Andrew Lewin Paid Member Paid Member

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    Hi Jon,

    Thanks for your reply.
    I'll certainly be having another go on my next day off. The experience was mildly traumatising at the time as I thought I'd ruined everything.

    The cam lobes on the new cam are a bit taller than the standard one. Is there any chance that could be my issue? It was almost like the valve springs were over-compressed.

    I'll admit I cheated when I fitted and refitted both cams in that I didn't set the timing from scratch, instead opting to knock off the cam sprocket first and holding the whole belt assembly static.

    Without immediate access to a timing light, and needing the car to be functional for my Monday morning commute, I was being extra careful throughout the whole process.

    Thanks again, Andrew.
     
  4. Jon Olds Forum Junkie

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    No chance the lobes will hit really. Its only mega race cams that need clearancing.
    Knowing where to expect the the lobes to be when the piston is at the top (on No.1 say) is key
    Jon
     
  5. davidut5 Forum Member

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    Is the cam correct for the engine? Hidraulic or solid lifter?
    Scratch that, maybe check if the cam alone rotates freely, with pistons halfway down.
     
  6. Jon Olds Forum Junkie

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    agree, cam needs to rotate
    Jon
     
  7. Andrew Lewin Paid Member Paid Member

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    Ok. So day off today and time to have another crack at this job.

    Got all the way down to the camshaft again which was necessary anyway since I'd cocked up the timing belt when putting it all back together the last time.

    Re-refitted the new/old GTI "g" cam and torqued the caps down slowly having set all the pistons to midway.

    Went to give just the camshaft a spin and low and behold, nothing. Wouldn't budge an inch.
    It would actually seem that the cam lobes are fouling the head!

    [​IMG]

    Needless to say I hastily removed the big cam and re-re-refitted the stock one. Managed to get the timing right this time and got the car back to working again.

    So what's up? Is this actually a solid lifter cam that I've been missold? Is it from some other VAG application perhaps? Annoyingly the only clear identification mark is the "g" at the sprocket end and "1939" halfway down. Everything else is illegible.

    Still head scratching, Andrew.
     
  8. davidut5 Forum Member

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    I got a gti pb hidro cam for my 1.6 also has a g on it.
    Maybe your gu is solid lifter, have you checked one of them tappets?
    Here are a few pics with it.
     

    Attached Files:

    Last edited: Jul 7, 2020
  9. davidut5 Forum Member

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    This definitely doesnt look like a stock gti camshaft.
     

    Attached Files:

  10. Andrew Lewin Paid Member Paid Member

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    Hi David,

    Thanks for posting some pictures. Your cylinder head is a lot cleaner than mine! ‍♂️

    I'm almost certain my head is hydraulic. It's got 4 caps instead of 5 which I believe is the tell-tale sign.

    I'll try and post more pictures from of my engine and of the "g" cam I have.

    Andrew.
     
  11. Andrew Lewin Paid Member Paid Member

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    [​IMG]
    [​IMG] [​IMG] [​IMG]
    Images of the stock setup
     
  12. Andrew Lewin Paid Member Paid Member

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    [​IMG] [​IMG] [​IMG]
    Trying this mystery "g" cam for size
     
  13. Jon Olds Forum Junkie

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    Few things, earlier cam pics don't look too great on the lobe surface finish. Later cam looks to have a lot more lift. A ten quid plastic
    battery Vernier is a great investment. Measure thighest part of the cam lobe, measure the smallest diameter. Subtract. That's the valve lift (yes, I know lash)
    Good starting point to know what you have got
    11.5 to 12mm you will have possible interference with the head casting, not good
    Jon
    Cams need a shiny polished finish, they 'rub' through the oil film to move (and spin) the round cam follower. If its cratered there's something wrong
    Jon
     
  14. Andrew Lewin Paid Member Paid Member

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    Thanks once again Jon,

    I'll be grabbing my verniers from work when I'm back in tomorrow.

    Out of interest, David, do you know what the measurements that John refers to are on your "g" cam from that PB engine?

    Andrew.
     
  15. rubjonny

    rubjonny Administrator Staff Member Admin

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    1st thing that leaps out at me on the new cam, all the bearing surfaces are clean. if it was a hydro cam from a mk1/2, you would have a dirty surface to match the missing cam cap
     
  16. rubjonny

    rubjonny Administrator Staff Member Admin

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    looks like it may be EV/DX solid lifter, they still have a G mark. look for the 026 mark as well as the G to ID a hydro cam:
    Clipboard01.jpg
     
    erreesse likes this.
  17. davidut5 Forum Member

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    Not only dirty but bigger diameter on the missing cap, it does look like the 1.8gu solid cam that i have.
    I remember comparing mk3 8v 2.0 cam to the mk2 gti pb cam and valve lift was the same 10.6mm, total lobe height 44.60mm and lobe thickness 34mm.
     
  18. Andrew Lewin Paid Member Paid Member

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    Wow, i'm blown away at the help i've received guys, truly.

    Many thanks to Jonny for the detailed cam identification guide and thanks again to David for more tech info too.

    So from the looks of it, would you agree that this technically is a GTI cam as the person I purchased it from described?
    From ebay it had the description:

    "Mk2 Golf Gti 8v Cam Shaft. Condition of cam is very good. Minor scoring on the bearings. Standard GTI cam from a 1.8, could also be used as an upgrade for a non-GTI 1.8 or 1.6 engine. ‘G’ cam."

    However, it appears, a GTI cam from an earlier solid lifter engine thus confirming its incompatibility with my head. My suspicion is that I need to locate a GTI cam from a later car with a PB engine code. Does this sound right?

    And now of course, resell the cam I purchased. Bugger.

    Andrew.
     
  19. rubjonny

    rubjonny Administrator Staff Member Admin

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    yep mk2 gti up to 1987 use the solid lifter type cam same as the mk1 so the ebay seller is correct there, after that you got the hydro ones. PB cam will always be hydro so you know its right for you, but late MK2 EV kjet were also hydro as well. I have heard the DX and EV hydro cams are ever so slightly better than the PB grinds but not sure how true that is, and never bothered to look into it in any detail as my 8v was always destined to be replaced by a 16v was just a matter of when I could afford it :lol:
     
  20. FiTekno New Member

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    Audi 2.0E (3A engine) has that cam with G mark. It has more lift than 1.8 8v, for example.
     

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