sparkplug portrusion

Discussion in 'PSI Superchargers Tech Questions' started by Brad671, Jan 28, 2010.

  1. Brad671

    Brad671 Member

    Joined:
    Mar 16, 2005
    Messages:
    53
    Likes Received:
    0
    sparkplug protrusion

    How far should sparkplugs protrude into the combustion chamber? I have some that are almost exposing the first thread and others that are only just exposing the base ring.
    Regards,
    Brad
     
    #1
    Last edited: Jan 28, 2010
    Brad671, Jan 28, 2010
  2. Bottlefed

    Bottlefed New to Blowers

    Joined:
    Feb 20, 2008
    Messages:
    375
    Likes Received:
    0
    This should be an interesting thread...I look forward to hearing how people feel on this also.
     
    #2
    Bottlefed, Jan 28, 2010
  3. Mike Canter

    Mike Canter Top Dragster
    Staff Member

    Joined:
    Mar 10, 2004
    Messages:
    4,630
    Likes Received:
    189
    Well several things here. The first being why different plug depths? I would guess previous head damage that has resulted in welding up the damage. The next thing then if that is so then the CC of each chamber may be different so the compression ratio from cylinder to cylinder may be different.

    The plugs protruding into the head could result in that part of the plug becoming a glow plug and cause pre-ignition.

    Lastly, if the plug is out into the chamber then reading the plugs accurately may be hard. I would think that the plug that is hanging it out into the chamber would read hotter and therefore indicate leaner than it is. It would be hard to balance the cylinders based on plug reading.
     
    #3
    Mike Canter, Jan 28, 2010
  4. Chris Bennett

    Chris Bennett Member

    Joined:
    May 8, 2005
    Messages:
    84
    Likes Received:
    0

    If you ever have cylinder chamber damage with an exposed spark plug thread some of the material can get stuck to the thread and it will damage the threads of the spark plug hole as you take the plug out after a run. Just another expense you'll have to dish out when you get your heads repaired.
     
    #4
    Chris Bennett, Jan 28, 2010
  5. Brad671

    Brad671 Member

    Joined:
    Mar 16, 2005
    Messages:
    53
    Likes Received:
    0
    The heads are undamaged the only reason I found out the plugs were protruding differently was because I was CCing them to get a accurate CR.
    So I'm going to use indexing washers to fix the different depths but still need to know how far they should protrude into the chamber.
    Any help much appreciated.
    Regards,
    Brad
     
    #5
    Brad671, Jan 29, 2010
  6. tc1216

    tc1216 Member

    Joined:
    Dec 13, 2005
    Messages:
    98
    Likes Received:
    1
    There should be NO exposed thread. They should be flush with the chamber, any exposed threads could be a source of hot spot to cause detonation, and the exposed thread can pick up some crud and rip the threads out when you remove the plug.
     
    #6
    tc1216, Jan 29, 2010
  7. Brad671

    Brad671 Member

    Joined:
    Mar 16, 2005
    Messages:
    53
    Likes Received:
    0
    So the base ring should be flush with the chamber or the first thread?
     
    #7
    Brad671, Jan 29, 2010
  8. backmotor

    backmotor Owner/Crewchief/Test Pilot

    Joined:
    Jan 1, 2004
    Messages:
    246
    Likes Received:
    1
    This is about as much as I would like to see on my BBC :D

    [​IMG]
     
    #8
    backmotor, Jan 29, 2010

Share This Page





XenPorta 2 PRO © Jason Axelrod from 8WAYRUN.COM