R5A(Gorde)1397cc

  1. reidalpine Enthusiast

    Messages:
    1,356
    Location:
    Norway
    Any of you familiar with the 840 X-XX motor (fx. r1223) -when lifting off alu-top I find some quite accentuated marks in all 4 combustion-chambers-All situated in the squishband area .All pretty the same courseness. Looks like someone has banged on a flat screwdriver and left marks in a random criss-cross pattern..
    These "marks" is also to be found at corresponding/same location on each piston-crowns

    First thought were massive pre-detonation :o but then I thought..could these corrugations-marks
    be there for a reason? namely to make the fuel/air move into squishband in a kind of erratic/swirly
    way?

    Or have I finally closed the circle to full-blown madness???? :whistle:

    Looking at Malcoms pixes showing head and top of pistons I can't see these marks at all,maybe they're
    not on aftermarked pistons,and might have been removed in head when it was rectified ???

    Also I noticed the arrows on all 4 pistons-crowns on mine has the arrow (that I've always believed should point 2wards flywheel) is pointing 2wards the timing-chain. Untill I noticed the squish-area on pistons corresponds with same area in head.... So Must be right -right?

    I'm near the end of mission of bying in new parts one or two smaller items left then its all personell to the
    pumps here....Even found the 1,9mm head-gasket (gr.2) as the compression is already high enough..


    PS: I just saw an ad on LBC right now showing the same "pattern" inside head,which made me feel a
    little better (the 4 Kronenbourg Had nothing 2 do with it) then again-other ads does not have them ??

    What says the tech-brigade ???

    -As always;Any/All well informed info/tips greatly appreciated! Thanx in advance.. -Reid.
     
    Last edited: Aug 8, 2018
  2. malcolm

    malcolm & Clementine the Cat Staff Member

    Messages:
    4,048
    Location:
    Bedford UK
    Yes I think you have gone mad - there are no photos! I think they are needed here!
     
  3. reidalpine Enthusiast

    Messages:
    1,356
    Location:
    Norway
    Hehe-you might be right there Malcolm! -I've plugged the plugholes in the head and filled up with diesel to let soak some.
    it's just too solid to see properly whats what..but I think No 3 looks as if there's been bits or pieces rummaging around on
    top of the piston and towards squish-area..small(ish) cuts and chips on surface of these areas.
    - I'll have another look tomorrow or thereabouts,and hopefully have some pixes too-
    This bleeding Canon camera EAT & SH**TS batteries .put in new ones.Blank one pole.pick it up to take pic.remove blank turn-on and it says
    replace battery... Must be made in same rathole as MitsuBITCH if you ask me.. Oh well... -Reid.
     
  4. malcolm

    malcolm & Clementine the Cat Staff Member

    Messages:
    4,048
    Location:
    Bedford UK
    Does sound like it could be detonation. I had some in one of my Gordini heads and it looked as if a valve had been floating around in there. They really need 98 octane fuel and are very sensitive to the timing curve.

    I replaced my distributor with a programmable 123 dostributor and that works well. I can send a modern petrol curve as a starting point if you go that way.
     
  5. reidalpine Enthusiast

    Messages:
    1,356
    Location:
    Norway
    Hi again Malcolm. It looks like pre-detonation to me,and that was my initial thought too.
    Luckily it seems poss to "shave" it off which again will leave me with a tad better (lower) comp

    Did you manufacture your own stem for the 123 to make it fit? I've just got info they have now
    started production of 3 different 123units to fit the R5A with no furter mods,so am waiting till
    I've decided Which version to go for.the one with 16(?) set curves or one of the 2 mappable ones

    Just checked prices for head-work: w/o valve/bridge £450, incl. valves etc £650 -of course as
    we're all (supposedly)Billionaires over here no-one raises an eyebrow.Anyways I want all necess-
    ary work done properly so I end up with a Finished all prepared head-unit.

    If ok I'll get back re the starting curves-Thanx for offering Malcolm! -Reid.
     
  6. malcolm

    malcolm & Clementine the Cat Staff Member

    Messages:
    4,048
    Location:
    Bedford UK
  7. reidalpine Enthusiast

    Messages:
    1,356
    Location:
    Norway
    Thanx for that tip Malcolm. I agree re.the programmable as this gives poss to finetune to great extent,especially nice if/when going for
    other jetting/carbs or other mods -R.
     
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