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Technical Sbc smashes sparkplugs

Discussion in 'The Hokey Ass Message Board' started by Alex Gillman, Jan 6, 2021.

  1. Alex Gillman
    Joined: Nov 5, 2019
    Posts: 30

    Alex Gillman

    I have never seen this, and can't figure out why it is happening. It is off and on. I changed my plugs yesterday with NGK TR55 plugs to replace my old Autolites but the piston smashed the ground on 5 of the 8 plugs. I replaced them with the old ones and it ran fine until I tried to fire it up this morning and it smashed the Autolights. There is no water in the oil either. Any ideas?

    Thanks,
    Alex Image%20(1).jpeg Image%20(2).jpeg Image%20(3).jpeg

    Sent from my SM-G960U using The H.A.M.B. mobile app
     
    Jalopy Joker likes this.
  2. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 12,690

    Johnny Gee
    Member
    from Downey, Ca

  3. Baumi
    Joined: Jan 28, 2003
    Posts: 3,046

    Baumi
    ALLIANCE MEMBER

    There are different plugs for Chevys, like AC R43 S or R45S with a washer and short threads and AC R45TS with a conus seat and longer threads... I have no idea what the NGK numbers are, but your plugs seem to be for the later heads, they still look pretty long threaded from here to me.
     
    RICH B and Deuces like this.
  4. Try a spacer.

    My guess? Piston dome is smashing the spark plug. Could be the gap between the piston and head wasn't checked during build. Or the heads were angle cut for more compression, same result.

    Another thing to try, thicker head gasket.
     

  5. dana barlow
    Joined: May 30, 2006
    Posts: 5,126

    dana barlow
    Member
    from Miami Fla.
    1. Y-blocks

    Wrong plug for head used ? Would be my guess.
    The plus in photo are a bit longer thread then what many older heads take.
    Have you added or checked head ? Or maybe have pistons/pop -ups been added?
     
    Boryca, Deuces, little red 50 and 2 others like this.
  6. Baumi
    Joined: Jan 28, 2003
    Posts: 3,046

    Baumi
    ALLIANCE MEMBER

    Deuces likes this.
  7. ROADSTER1927
    Joined: Feb 14, 2009
    Posts: 3,144

    ROADSTER1927
    Member

    Put in shorter thread plugs or you have a MAJOR PROBLEM!
     
    getow, Deuces, VANDENPLAS and 3 others like this.
  8. Harv
    Joined: Jan 16, 2008
    Posts: 1,000

    Harv
    Member
    from Sydney

    Those plugs have an 18mm plug reach. Assuming this is a HAMB friendly Gen1 SBC, that’s a lot of reach. The plugs I run locally are only 9.5mm reach.

    Cheers,
    Harv
     
    Deuces, Johnny Gee and Alex Gillman like this.
  9. fortynut
    Joined: Jul 16, 2008
    Posts: 1,038

    fortynut
    Member

    What kind of hammer does it use?
     
    texasred and Deuces like this.
  10. Alex Gillman
    Joined: Nov 5, 2019
    Posts: 30

    Alex Gillman

    Deuces and Baumi like this.
  11. Budget36
    Joined: Nov 29, 2014
    Posts: 13,274

    Budget36
    Member

    The electrode needs to just reach into the chamber, see how deep the thread holes go and compare to your plugs.
     
    Deuces likes this.
  12. Alex Gillman
    Joined: Nov 5, 2019
    Posts: 30

    Alex Gillman

    I think I used the wrong plugs. It has 3947041 heads.
    Sent from my SM-G960U using The H.A.M.B. mobile app
     
    vtx1800, dana barlow and Deuces like this.
  13. Mike VV
    Joined: Sep 28, 2010
    Posts: 3,042

    Mike VV
    Member
    from SoCal

    I see you indicated the heads..!
    You are using completely...the wrong spark plug..!
    I'll bet the threads in your heads are only about .375" long. I'd say...you've got the wrong plugs.

    Get the proper spark plug for the heads that you have...you should be fine..!

    Mike

    P.s. - Hopefully...you didn't break a piston..!
     
  14. Baumi
    Joined: Jan 28, 2003
    Posts: 3,046

    Baumi
    ALLIANCE MEMBER

    Your heads are late 60s early 70s 64 cc 350 heads, pretty good heads for factory heads. But I bet you´ll need The TS spark plugs like AC R45TS
     
    Deuces likes this.
  15. larry k
    Joined: Feb 23, 2009
    Posts: 548

    larry k
    Member

    Don’t those 041 heads use the big plugs with the sealing washer on them .??? But they are shorter on the threads !
     
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  16. TCATTC
    Joined: Oct 12, 2019
    Posts: 283

    TCATTC
    Member

    Mine do, R45 or R45S
     
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  17. getow
    Joined: May 9, 2016
    Posts: 305

    getow
    Member

    How did it run, and for how long with da Autolites initially? Is this a new build or something changed or added like heads, timing chain? Not enough info?
     
    egads and Deuces like this.
  18. larry k
    Joined: Feb 23, 2009
    Posts: 548

    larry k
    Member

    After doing some checking , you got the wrong size, wrong kind, wrong length, plug . those are 5/8 dia hex. You want the old 3/16 dia hex plug with the sealing ring. I don’t see how they ever sealed to the head. ??? . 041 is a good horsepower head , but needs the old style plugs .....!
     
    Deuces likes this.
  19. The reason that sometimes they contact and sometimes they don't is probably that there is one index angle where they don't touch and as soon as you remove the plugs and switch them around in a different order, they angle different in each hole and they hit.
    But regardless, they are too long. Get the shorter plugs as many have recommended.
    You may want to "scope" the piston tops to see if the witness marks go all the way through.
     
    Deuces and brigrat like this.
  20. vtx1800
    Joined: Oct 4, 2009
    Posts: 1,719

    vtx1800
    ALLIANCE MEMBER

    @Alex Gillman I did the same thing on a set of 041 heads...........felt sorta stupid, I used the wrong style of plugs, I finally figured out what the heads came on and then looked at the application chart. I don't have that handy or I'd tell you what number to use.
     
  21. 427 sleeper
    Joined: Mar 8, 2017
    Posts: 2,896

    427 sleeper
    ALLIANCE MEMBER

    If you wat to stay with NGK plugs, try R5670-7's. They're .375 reach, 13/16 hex - gasketed, and non-resistor. Not sure what the resistor type number would be though.
    Got a pic of the spark plug hole? Send us a pic so we know what you're dealing with.
     
    Last edited: Jan 7, 2021
  22. squirrel
    Joined: Sep 23, 2004
    Posts: 56,085

    squirrel
    Member

    chevy changed plug type in 1970. If they are gasket type, use something like R45S. If they're tapered type, use something like R45TS.

    date code on the head might tell you, looking carefully at the hole the plug seats in will also tell you.
     
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  23. Mr48chev
    Joined: Dec 28, 2007
    Posts: 33,983

    Mr48chev
    ALLIANCE MEMBER

    ^^^^^ THIS!!!!!!. You have to make sure which spark plug seats the heads have but either way they use he short thread plugs.
     
  24. Dusty roads
    Joined: Nov 29, 2016
    Posts: 127

    Dusty roads
    BANNED

    If you can't find the correct spark plug try index washers.
     
    loudbang likes this.

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