840A head

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    I have a 1935 840A with a cracked head. It has the large spark plugs. Is this the correct head for this car or is it supposed to have the head with the smaller plugs. I would like to find the correct replacement head if possible. Any leads on a head wuld be appreciated. Thanks, Derek


    I believe that the small sparkplugs were used in 1935. I do have a reproduction 1936 aluminum head, polished, that I would sell. Including the polishing, I have $1400 invested. I would sell the head for half that. This head was standard from 1936-1938. Please speak to someone knowledgable about these aluminum heads before you consider buying mine. I could deliver this head to Hershey, if anyone else is interested. Tony


    Hi Derek,

    1934 and 1935 (including 836A) used small spark plugs in cast iron heads. 1933 and earlier used large plugs.

    Here is some other info to help identify heads:

    1933 (and all later except possibly an 836A) had a tapped hole in the left side of the head, about 15" from front, to mount the oil cooler.
    1932 and earlier did not have this hole.

    1929 (only) had 2 holes to mount the oil filter on the left side near the front.

    1929 thru 1935 had a raised water outlet, about 1.75" above the top surface, 1936-38 aluminum heads did not, so they look quite different.

    All heads had a number stamped on the flange surface of the water outlet, but over the years they get machined or rusted off. The correct number for your car is #6 (140hp).

    A 1933 head (and ’34-’35 836A) will give a little more hp on your engine (145), a 1936 the most (150), ’29-’32 a little less (132-135).

    If the crack is at the base of the water outlet (typical) or some other non-critical area, it can be loc-stitched with threaded tapered interlocking plugs. I ran my ’33 for years with this type of repair.

    Welding is a tricky business, but some can do it, raising and lowering the temp of the whole head slowly over a day each way.

    Hope this helps.

    Bob Jacobsen


    I am still looking for a cast iron head with small plugs to fit my 1935 840A. Thanks to those of you who have responded to my posting. I would prefer to use the correct head for my year if one is available. Anyone out there with the correct head that they are willing to part with? Thanks, Derek Van Alstine

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