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Is this normal in the combustion chamber?

Posted by Simonsaysr1, May 14, 2019

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  1. Simonsaysr1

    Simonsaysr1 Proven Member

    100
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    Joined Jan 30, 2016
    Rocky mount, North Carolina
    I noticed some weird pits in the cylinder head combustion chamber? Wouldn't this create a hot spot? What would cause this?
     

    Attached Files:

    Street Build 211  1

    1997 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  2. jakk220

    jakk220 Proven Member

    1,134
    234
    Joined Nov 13, 2010
    Akron, Ohio
    Looks like marks caused from detonation. What does the Piston look like in that cylinder?
     
    Last edited: May 15, 2019

    218  1

    1991 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM

    1K  3

    1997 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM

    Street Build 1K  1

    1993 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM
    Loading...
  3. tk106

    tk106 Supporting Member

    1,208
    216
    Joined Sep 11, 2017
    Cincinnati, Ohio
    I think it’s sh**ty casting and or sh**ty aluminum. Had the same in only 1 & 4. Used 320 grit on dremel but didn’t remove too much since it was my first time messing with the head 22ABA6DD-C407-40EF-B82C-AD416258D92C.jpeg B6873F94-9F2E-4B08-8956-BF24C5415A56.jpeg A031E21F-0273-44C7-9B47-258808F14817.jpeg 0CAB2E2B-CF5C-4A24-9D72-7E2741097530.jpeg
     

    70  3

    2000 Jeep Cherokee Sport - Classic
    awd · automatic · Misc Vehicles

    111  4

    93 Civic 4 Door -sold-
    fwd · manual · Misc Vehicles

    Street Build 1K  6

    1992 Eagle Talon TSi AWD
    12.625 @ 111.42 · 1G DSM
    Loading...
  4. motomattx

    motomattx Proven Member

    1,636
    455
    Joined Dec 9, 2010
    wampum, Pennsylvania
    Lots of them look just like that, likely detonation damage from just the stock tune on the hot corners of the chambers.
     

    Drag Race Build 2K  16

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  5. tk106

    tk106 Supporting Member

    1,208
    216
    Joined Sep 11, 2017
    Cincinnati, Ohio
    Mine was only 1&4. Wouldn’t all 4 chambers be the same if it was detonation?
     

    70  3

    2000 Jeep Cherokee Sport - Classic
    awd · automatic · Misc Vehicles

    111  4

    93 Civic 4 Door -sold-
    fwd · manual · Misc Vehicles

    Street Build 1K  6

    1992 Eagle Talon TSi AWD
    12.625 @ 111.42 · 1G DSM
    Loading...
  6. ThunderChild

    ThunderChild Supporting VIP

    2,431
    643
    Joined Jan 5, 2012
    Rathdrum, Idaho
    I agree with @tk106 I see it on alot of the heads I pull, I'm thinking casting flaws, and they always seem to be worse on the end cylinders.
     

    Street Build 106  3

    1990 Plymouth Laser N/T
    fwd · manual · 1G DSM

    229  8

    1987 Toyota Pickup/Hilux
    awd · manual · Misc Vehicles

    Street Build 743  7

    1997 Mitsubishi Eclipse Spyder GST
    fwd · manual · 2G DSM

    Street Build 942  1

    1992 Eagle Talon TSi AWD
    manual · 1G DSM

    Street Build 2K  10

    1992 Eagle Talon TSi AWD
    awd · manual · 1G DSM
    Loading...
  7. silvreclips

    silvreclips Proven Member

    918
    90
    Joined Jul 19, 2005
    Greenville, South Carolina
    It's common to only see detonation marks on 1 or 2 cylinders.
     
  8. EVLGSX

    EVLGSX Proven Member

    351
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    Joined Dec 7, 2017
    Wallingford, Connecticut
    Ive always seen the same
     

    Street Build 1K  8

    1997 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM
    Loading...
  9. motomattx

    motomattx Proven Member

    1,636
    455
    Joined Dec 9, 2010
    wampum, Pennsylvania
    Not really, those cylinders are likely the lean ones or the hot spots on the cooling system.
     

    Drag Race Build 2K  16

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  10. jakk220

    jakk220 Proven Member

    1,134
    234
    Joined Nov 13, 2010
    Akron, Ohio
    Yeah I have had it where it was only on one cylinder before. Its actually not uncommon. Here is a pic of my old 1g that had detonation marks on cylinder 4 only. Had the same marks on the head too.

    rrbGNaD7CXJxIX1Ghi9b8IxgUwjzVg87xas63bF8umEGR27yUR-7hmXTU17yYHCqZ5c0FbrHz5TjxPpY0gI=w493-h657-no.jpg
     
    Last edited: May 15, 2019

    218  1

    1991 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM

    1K  3

    1997 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM

    Street Build 1K  1

    1993 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM
    Loading...
    tk106 likes this.
  11. 1990TSIAWDTALON

    1990TSIAWDTALON Moderator

    4,011
    1,569
    Joined Nov 14, 2013
    Independence, Kansas
    Take emery cloth to it by hand and just smooth out the spots so they don't get hot. Don't touch the fire ring area.
     

    278  17

    1967 Chevrolet Camaro RS
    rwd · automatic · Misc Vehicles

    Street Build 395  4

    1998 Eagle Talon TSi
    fwd · manual · 2G DSM

    Street Build 3K  21

    1992 Eagle Talon TSi AWD
    awd · automatic · 1G DSM

    Street Build 5K  11  25

    1990 Eagle Talon TSi AWD
    13.620 @ 108.460 · 1G DSM

    4K  24

    1990 Eagle Talon TSi AWD
    13.612 @ 107.760 · 1G DSM
    Loading...
    tk106 and Simonsaysr1 like this.
  12. jakk220

    jakk220 Proven Member

    1,134
    234
    Joined Nov 13, 2010
    Akron, Ohio

    218  1

    1991 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM

    1K  3

    1997 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM

    Street Build 1K  1

    1993 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM
    Loading...
  13. tk106

    tk106 Supporting Member

    1,208
    216
    Joined Sep 11, 2017
    Cincinnati, Ohio
    If you guys say so. Just strange to me it's always the end chambers.
     

    70  3

    2000 Jeep Cherokee Sport - Classic
    awd · automatic · Misc Vehicles

    111  4

    93 Civic 4 Door -sold-
    fwd · manual · Misc Vehicles

    Street Build 1K  6

    1992 Eagle Talon TSi AWD
    12.625 @ 111.42 · 1G DSM
    Loading...
  14. Simonsaysr1

    Simonsaysr1 Proven Member

    100
    6
    Joined Jan 30, 2016
    Rocky mount, North Carolina
    Looks completely fine. Nor did I ever have knock really occur. I never noticed any audible detonation either
     

    Street Build 211  1

    1997 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  15. Simonsaysr1

    Simonsaysr1 Proven Member

    100
    6
    Joined Jan 30, 2016
    Rocky mount, North Carolina
    I'll sand it out carefully I think it's a casting imperfection as well. My pistons look fine and it only appears to be on the ends of the head . Definitely caught my attention
     

    Street Build 211  1

    1997 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
    1990TSIAWDTALON likes this.
  16. ThunderChild

    ThunderChild Supporting VIP

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    Rathdrum, Idaho
    If you look at where the marks are on the head, they're off to the sides/ends. Then look at @jakk220 's pic And the detonation is closer the the valve edges, close to the quench area where detonation would start to occur. I'm not saying it's impossible for detonation to occur up in the pocket, but I think it's highly unlikely for that area to see that amount of marking and the piston to not be destroyed, or have marks in a corresponding area.

    Like I said, I've seen at least a dozen of these heads with the same marks in the same spots, and I wouldn't be surprised if it's just a casting defect from foam cores boiling away, or gas in the sand making flow marks.
     

    Street Build 106  3

    1990 Plymouth Laser N/T
    fwd · manual · 1G DSM

    229  8

    1987 Toyota Pickup/Hilux
    awd · manual · Misc Vehicles

    Street Build 743  7

    1997 Mitsubishi Eclipse Spyder GST
    fwd · manual · 2G DSM

    Street Build 942  1

    1992 Eagle Talon TSi AWD
    manual · 1G DSM

    Street Build 2K  10

    1992 Eagle Talon TSi AWD
    awd · manual · 1G DSM
    Loading...
    tk106 likes this.
  17. tk106

    tk106 Supporting Member

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    Cincinnati, Ohio
    Jakks piston definitely show signs of detonation.

    You can remove the carbon in those pockets with a brass wire wheel on a dremel if you have one.
     

    70  3

    2000 Jeep Cherokee Sport - Classic
    awd · automatic · Misc Vehicles

    111  4

    93 Civic 4 Door -sold-
    fwd · manual · Misc Vehicles

    Street Build 1K  6

    1992 Eagle Talon TSi AWD
    12.625 @ 111.42 · 1G DSM
    Loading...
  18. Simonsaysr1

    Simonsaysr1 Proven Member

    100
    6
    Joined Jan 30, 2016
    Rocky mount, North Carolina
    thanks for the tip. i was thinking about those little carbon pieces, I couldn't get to them with just emery cloth,
    seriously considering getting another head, but realllly dont want to dish out more money. my friend has one with bent valves, came off a 98 gsx(got to help him pull it for a 6 bolt swap). but i might have gouged the sealing area of the oil port tear drop. its all the way to the edge of the ring but stops right at it.. i tried so hard and it slipped forward and just hit the tip of the carbide. im going to double check it tomorrow with a head gasket. I'm seriously wanting to smack my self :ohdamn:for not doing the easiest thing to do like jafro said and put the old HG on it first(didnt bring it with me to work). I got impatient and we were slow at work so i decided to go in the back with the air dremel and I honestly should have done it on my own time , so i could have made sure i didnt make this mistake:notgood:.
     

    Street Build 211  1

    1997 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  19. tk106

    tk106 Supporting Member

    1,208
    216
    Joined Sep 11, 2017
    Cincinnati, Ohio
    Yikes. Yeah patience is key when it comes to things like this, as you already know. I just used a dremel on medium speed for the oil passage. Maybe it’s salvageable if you’re getting it decked???
     

    70  3

    2000 Jeep Cherokee Sport - Classic
    awd · automatic · Misc Vehicles

    111  4

    93 Civic 4 Door -sold-
    fwd · manual · Misc Vehicles

    Street Build 1K  6

    1992 Eagle Talon TSi AWD
    12.625 @ 111.42 · 1G DSM
    Loading...
    1990TSIAWDTALON likes this.
  20. Simonsaysr1

    Simonsaysr1 Proven Member

    100
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    Joined Jan 30, 2016
    Rocky mount, North Carolina
    i dont think so , the gouge is pretty deep and would taper to a bigger gap the lower it got resurfaced. , im hopping that when I put the gasket on it.. it is inside the sealing ring and I can continue. if not its more money and time i guess. I feel pretty confident when I try it tommorrow its going to just barely (i mean just barely) make it or be over cut. I sure hope its not toast.
     

    Street Build 211  1

    1997 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  21. EVLGSX

    EVLGSX Proven Member

    351
    131
    Joined Dec 7, 2017
    Wallingford, Connecticut
    This is an 80k never torn down 7 bolt. I pulled the head last year to change the HG and found the same thing as the OP. This is before it was really pushed. Id have a hard time believing this was the result of detonation after looking at those outer pistons but who knows.
    20181011_004433.jpg

    Not 100% sure how it got this way but I didnt want to leave it like this.
    20181012_175526.jpg

    I decided to fix what I found and ended up doing the valve job while it was off. Very easy to smooth out, the usual 80/ 180/ 320 by hand then some high speed rotary stuff followed by polishing. Go easy and stay away from the valve seats.
    20181012_175534.jpg

    And heres is where I ended up with it.

    20181013_184407.jpg
     

    Street Build 1K  8

    1997 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM
    Loading...
    ThunderChild, Simonsaysr1 and tk106 like this.
  22. ThunderChild

    ThunderChild Supporting VIP

    2,431
    643
    Joined Jan 5, 2012
    Rathdrum, Idaho
    Yep seen the same thing on lots of Hyundai heads with low miles and several dsm heads. Still voting casting flaws. But nice job on the clean up @EVLGSX ! I have a few heads with similar CC issues and im doing the same thing to them currently.
     

    Street Build 106  3

    1990 Plymouth Laser N/T
    fwd · manual · 1G DSM

    229  8

    1987 Toyota Pickup/Hilux
    awd · manual · Misc Vehicles

    Street Build 743  7

    1997 Mitsubishi Eclipse Spyder GST
    fwd · manual · 2G DSM

    Street Build 942  1

    1992 Eagle Talon TSi AWD
    manual · 1G DSM

    Street Build 2K  10

    1992 Eagle Talon TSi AWD
    awd · manual · 1G DSM
    Loading...
    1990TSIAWDTALON likes this.
  23. jakk220

    jakk220 Proven Member

    1,134
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    Joined Nov 13, 2010
    Akron, Ohio
    Hmm. Now you guys are convincing me that it's something with the casting. I just chalked it up as a hot spot for detnation. But those last pictures look like casting flaws...
     

    218  1

    1991 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM

    1K  3

    1997 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM

    Street Build 1K  1

    1993 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM
    Loading...
  24. Crashmikejones84

    Crashmikejones84 Probationary Member

    2
    0
    Joined May 12, 2019
    Utica, Indiana
    Most likely from detonation as he stated previously. I would also check your valve seats and exhaust valves for pitting. Very common on these when running too much boost without the extra fuel or a knock sensor that's not functioning properly. Check the ring lands for excessive clearance and also make sure from the top ring land to the top of the piston you dont see any deforming. Ran into this on my 92 tsi, although much more extensive. Hope this helps
     

    102  1

    2005 Mercury Sable
    fwd · automatic · Misc Vehicles
    Loading...
  25. Simonsaysr1

    Simonsaysr1 Proven Member

    100
    6
    Joined Jan 30, 2016
    Rocky mount, North Carolina
    Here's the tear drop. I'm pretty sure it's toast
     

    Attached Files:

    Street Build 211  1

    1997 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...

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