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Hot Rods 331 Hemi oil leak through spark plug tubes

Discussion in 'The Hokey Ass Message Board' started by hambone2505, Jan 6, 2016.

  1. hambone2505
    Joined: Jul 8, 2011
    Posts: 62

    hambone2505
    Member
    from San Diego

    I have a 1954 331 hemi that was given to me by my very generous uncle, along with a 1927 roadster, all original Henry Ford steel.

    The motor was completely rebuilt by a reputable machine shop, then sat for a couple years before I completed the car. First fire up, primed the oiling system, set the ignition timing as close as possible, and it started up and ran beautifully. Shortly after, the body came off for paint and when I put everything back together I have been chasing problems ever since. Ive rebuilt the entire engine by now and had a machine shop go over the heads and do a regrind and had valve guides done. So theres no issues there

    So this brings me to last night. Pulled a plug and noticed there was a little bit of oil on top of the pistons, it wasn't soaked, but there were multiple wet/partially wet drops of oil. Pulled the valve covers off and looked into each plug hole and noticed the same thing, oil was getting on top of the pistons from somewhere. I noticed a spark plug tube that seemed like it had been stretched out where the plug seats. Come to find out that when the tubes were seated in the Hot Heads valve covers, they were still a half inch away from seating in the head. So there was a poor seal there, plus my 3/4 reach plugs were nowhere near being in correct proximity in the combustion process. Im guessing this is why I was getting weird readings on plugs and it just didn't sound right to my ears.

    I had been getting the 426 tubes from Bob at hot heads, which were supposed to be the correct tubes for their valve covers on my engine, which obviously they weren't. After some research, the tubes for my engine compared to the 426 tubes were about a 1/2" difference. Nothing against Bob or hot heads, I've done lots of business there and am a happy customer, its my fault for not doing the research on my end and communicating that to him.

    So Im just looking for some piece of mind that the tubes are the cause of the oil, and the fact that my plugs were nowhere near seated against the head?

    p.s. I did a compression test with engine cold, before I knew my plugs were 1/2" from being seated and properly sealed, trying to rule out bad or worn rings. Compression was low, 100, but it was pretty consistent on all 8 cylinders. No sign of bad rings, no smoke and not burning oil, I just wanted a little piece of mind
     

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  2. There are also supposed to be seals that go between the tubes and the valve covers.
     
  3. By the way, cool little roadster.
     
  4. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 18,207

    Jalopy Joker
    Member

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  5. hambone2505
    Joined: Jul 8, 2011
    Posts: 62

    hambone2505
    Member
    from San Diego

    Ya I have seals at the valve cover, just wanted to see if this oil leak made sense to someone besides me, since there wasn't a seal at the plug tube/head.
    And thanks for the compliment
     
  6. KoolKat-57
    Joined: Feb 22, 2010
    Posts: 2,344

    KoolKat-57
    Member
    from Dublin, OH

    I had thought of putting aluminum valve covers on the 392 in my '32, and I had heard of similar problems with tube length when using aftermarket valve covers.
    Thanks for confirming what I had heard, I guess I'll stick with the stock valve covers.
    By the way, that is one really sweet T, very nice build.
    I will be following this thread as you let us know how you make out.
    KK
     
  7. most likely everything is fine. when the plugs are removed oil runs down the hole onto the piston. after start up oil smoke will be blowing out the pipes. after the engine is up to temp that should all go away. bob walker does sell some pieces to help stop this. they do require machining to the head. the tubes were designed as a service part. the tube is the seal and was designed to wear out. also to get the proper plug depth the plug gasket needs to be removed. to keep the seal at the covers look into stanke motorsports. they offer a seal for that.
     
  8. Hambone, I believe your assessment is right.
    The seal is supposed to be formed when the sparkplug is tightened, squeezing the tube between the sparkplug and head.
     
    hambone2505 likes this.
  9. hambone2505
    Joined: Jul 8, 2011
    Posts: 62

    hambone2505
    Member
    from San Diego

    I'm familiar with the little bit of oil that seeps when you remove the plugs, but this is more than that. I measured out how long of a tube I will need from where the tube seats in the valve cover, to where it seats in the head. Comes out to 6-1/2", which happens to be what the original 1953 used with stock covers. The 426 tubes I have are just under 6", so I assumed that's where my leakage was occurring. I ordered the correct size tubes so hopefully it solves the problem.

    And the only way to get the proper plug depth is with the right size tube that actually seats all the way in the head. Fingers crossed
     
  10. hambone2505
    Joined: Jul 8, 2011
    Posts: 62

    hambone2505
    Member
    from San Diego

    Thanks, hopefully the other tubes get here before the weekend and I can put this issue to rest
     
  11. sunbeam
    Joined: Oct 22, 2010
    Posts: 2,855

    sunbeam
    Member

    If the tubes are steel use a spark plug gasket if aluminum no gasket.
     
  12. whats the difference with the tubes when all of the gaskets are steel. the engine was designed to not use a gasket. proper plug depth is reduced with the gasket. i would think if mother mopar wanted a gasket she would have put one there.
     
  13. hambone2505
    Joined: Jul 8, 2011
    Posts: 62

    hambone2505
    Member
    from San Diego

    Ive been around a few hemis for a couple years, and I've seen the tin and aluminum ones used. My uncle likes the aluminum ones, my other uncle likes the steel tubes, I think its just preference.

    As far as the washer and the plug depth, I don't know if an untrained ear would be able to tell. My 3/4'' reach plugs were only going in about half way due to the short tubes, and the engine still sounded really healthy. I just had that voice in the back of my head that something was off. One of those things that only you will hear.

    After I suspected the tubes being too short, I decided to torque one of the plugs to 30 ft/lbs. Ive done extensive research on the plug torque, because 30 ft/lbs seemed like a lot when I first saw that spec. All of a sudden it felt like I stripped the threads in the head, I pulled the plugs and valve cover and thats when I saw the bottom of the tube blown out and realized they were too short.

    I was going to machine the seats in the valve covers so the tubes would also seat in the head, but I ended up just ordering the right length tube.
     
  14. hambone2505
    Joined: Jul 8, 2011
    Posts: 62

    hambone2505
    Member
    from San Diego

    Also, are there any other 331 guys out there that know a little something about the head gaskets. Between cylinders 2&4,6&8, 1&3 and 5&7, right above the stud there is a port, I believe its water, but every head gasket out there covers up that hole for some reason. Anybody know why?
     
  15. I run chromed stock valve covers on my 331 and stock tubes. For sure they have to be the correct length because they ARE the seal whether made of steel or aluminum. Your problem is as you suspect, too short tubes causing no sparkplug seal.
     
  16. Dan Timberlake
    Joined: Apr 28, 2010
    Posts: 1,171

    Dan Timberlake
    Member

    I think Slant sixes use a similar set up, but all in the head, not thru the valve cover.
    Note the rubber seal at the top end of the tube.
    http://www.allpar.com/photos/bios/weertman/slant-six-engine.gif
    Curiously my 1968 Plymouth shop manual does not mention whether spark plug gaskets are used, or not.

    This is what Dodge said about installing the Red Ram engine's spark plugs in 1952
    http://www.imperialclub.com/Repair/Lit/Master/059/cover.htm
    http://www.imperialclub.com/Repair/Lit/Master/059/page10.htm
    http://www.imperialclub.com/Repair/Lit/Master/059/page11.htm

    They were concerned about the gasket pulling the plug .030" out of the chamber, never mind by 1/2 inch, and the loss of seal.
     
  17. garyf
    Joined: Aug 11, 2006
    Posts: 182

    garyf
    Member

    The spark plug gasket was not supposed to be used on the slant 6 with the spark plug tubes. The gasket cut into the soft aluminum tube a created an oil leak. Always thought this was the reason spark plug gaskets always came uninstalled on new spark plugs
     
    Last edited: Jan 7, 2016
  18. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 3,864

    Ebbsspeed
    ALLIANCE MEMBER

    On both my 354 and 392, I bought steel shims to use between the spark plug and the aluminum tubes. I don't know the exact size, but the OD of them is a bit larger than the base of the spark plug and about the same diameter as the id of the tube base, so the pressure of the plug against the aluminum is spread out a bit more, and doesn't crush the aluminum. You can measure carefully and order here, but best to just take a spark plug and tube to your local hardware store and figure out what size works.
    Shim.png
    http://www.mcmaster.com/#standard-shims/=10kx3ya
     
  19. as I said before the tubes were a service item. they were to be changed when needed. adding washers and gaskets for long life were not part of the original plan.
     
  20. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 3,864

    Ebbsspeed
    ALLIANCE MEMBER

    In this hobby a lot of "service items" are no longer available, so whatever can be done to make a part last a little longer without spending beaucoup bucks is the path I normally take.
     
    Last edited: Jan 7, 2016
  21. Gene Boul
    Joined: Feb 9, 2006
    Posts: 808

    Gene Boul

    I'm kinda shocked that you couldn't tell that the spark plug wasn't seated in the head. Regardless, The tube needs a gasket (o-ring") at the valve cover interface and no gasket between the spark plug and tube. It's relatively easy to look into the spark plug hole thru the installed tube, valve cover (with gasket) and determine if all is seated. In a competition Hemi the difference in stackup is made up in the ability of the spark-plug tube to "float" and seal because of the top "o-ring".
    There are pieces that can be added to the heads to form a barrier between oil pooled on the head and the spark plug hole. Later after market heads eliminated the need for this "adapter"...they have an "o-ring" machined into the spark plug recess.
     
  22. i second that.
     

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