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Thread tap sizes in block and heads

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    Thread tap sizes in block and heads

    I will hopefully soon start assembling the engine on our Stag. I would like to run a tap through all the threads in the engine to clean them up. Does anyone now what size and thread I need? Maybe it is best to buy a imperial kit?

    Also I saw mentioned that someone had tapped the piece between the engine and gearbox so it would be easier to undo in the future. Can anyone tell me the tap sizes and bolt lenghts needed for that also?
    Kirsti & Ian in Norway
    1973 Stag Mk2 (ex-USA), Mallard Blue, TV8 engine, Manual O/D

    #2
    An imperial set is what you need. No metric. Most are 5/16 and 3/8 UNC & UNF. If you look at the Torque Settings section of the ROM all the thread sizes are shown.
    Dave
    1974 Mk2, ZF Auto, 3.45 Diff, Datsun Driveshafts. Stag owner/maintainer since 1989.

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      #3
      It was me who taps the gearbox adaptor plate. The thread is 3/8 UNC the same as the exhaust manifold to cylinder head bolts.

      I just ordered a set of Stainless Stag exhaust manifold bolts from some ebay supplier and used those for the gearbox, there were more than I needed for the job, but I am always needing new bolts anyway.

      Neil
      Neil
      TV8, efi, fast road cams and home built manifolds. 246bhp 220lbft torque

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        #4
        .... and be wary of buying an all-singing and dancing kit where money has been saved on the material quality! A snapped tap-in-a-hole can really rain on your parade. I've got some basic grips and chucks, but order individual taps and dies from a good source like Chronos in St.Albans (although I think they've moved to Luton or Dinstable now)

        Drew
        If you can't say something nice, don't say it !

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          #5
          Another very good supplier is Tracy tools. www.tracytools.com
          If you are only cleaning up existing tapped holes then you need only buy a plug tap. If you tap the plate for the gearbox mounting then you will need a first and probably a second tap but no plug tap. I alway recommend hss rather than the cheaper carbon for cutting threads in steel. Carbon is ok for aluminium alloys.
          John
          1978 Stag Brooklands Green; 1986 Porsche Carrera SC

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            #6
            Thank you guys! I found a kit local that has the sizes we need. I am amazed to see the amount of crud that came out of the head stud holes after refreshing the threads.

            I have ordered the SS exhaust bolts and will tap the holes when they arrive.
            Kirsti & Ian in Norway
            1973 Stag Mk2 (ex-USA), Mallard Blue, TV8 engine, Manual O/D

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