Bad Threads in Head

Unknown
Unknown
edited November -1 in HUDSON
I've slowly started to work on the Hornet that I 'rescued' 3 years ago and have been delighted at the great information and helpfulness on this forum and other member's sites. It does not run and I have been taking the engine apart. My car came with most of the Twin-H setup and has a 232 iron head. I believe that the car sat unused for 30 years in Missouri and developed corrosion on and around the spark plugs and the threaded holes in the head. I bought new Autolite plugs and screwed them in the holes, but not all plugs seem to thread on well and seem a bit loose. I fear that the part of the threads have rusted away causing poor fit and too much clearance. How can the threads be repaired?



I read an article about Jack Clifford's drag racing in the 50's and it talked about the various speed equipment that he used, including the severe duty, high altitude 232 head. The casting number referenced was 309391 and that is not the number on my head. Does anyone know the design difference between the 232 heads?



Hal

Comments

  • Unknown
    Unknown
    Helicoils may help on the worn/stripped spark plug threads.
  • [Deleted User]
    [Deleted User]
    Greenhornet, where in Tennessee are you?
    Bob Hickson
    Newport, TN
  • Uncle Josh
    Uncle Josh Senior Contributor
    Thread repair kits are available at parts stores. You'll get an oversize tap, and bushings threaded tap size outside, and 14mm inside. Tap the bad hole, screw the bushing on the spark plug with anti-zeize (always on plugs), put the locktite-type thread sealer on the outside of the bushing and screw it in. Voila!



    Or, find a replacement head for a 308. A little less compression, but unless you're racing it, you won't know the difference, and it'll be less stress on the bearings etc.
  • Unknown
    Unknown
    thanks for your help



    Bob, I'm near Chattanooga.



    Hal
  • Unknown
    Unknown
    Hal

    The term "Severe Duty Parts" were the buzz words used for NASCAR racing components available through the normal dealer parts network. The severe duty 232 cylinder head was a cast iron assembly with small combustion chambers and 1/2 inch head bolt holes. This gave the 308 Hornet (7X) engine high compression and improved head gasket holding with 1/2 head bolts vs the stock 7/16.

    Fred
  • [Deleted User]
    [Deleted User]
    From your description, I would go for a replacement head. There are lots of them out there. As to yours, most speed shops can clean your head up and repair any threaded areas including spark plug holes. I had one done recently and they fixed two plug holes and chased the rest of the threads for 65 dollars. They used something other than helicoils. Don't remember what they called them. I cannot tell anything was done by looking at them.
  • Uncle Josh
    Uncle Josh Senior Contributor
    If a machine shop did it, they probably fixed it permanently. The method is to drill and tap the hole at least 1/4 inch bigger and thread a piece of stock in there and seal it, machine it flush, put a 'dutchman' at the thread line so it can't rotate, and retap to 14 mm.
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