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Help identify thread/pitch of holes in 5.0 block I need to fill

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  • Help identify thread/pitch of holes in 5.0 block I need to fill

    I have a question I'm hoping someone here can answer. For some reason this info isn't easy to find using Google and the internet.

    I've got a late model 5.0 block that I'm building for my brother's 68 couple. I don't have another 5.0 handy to cross reference with.

    Its got a lot of holes in it for things I assume are sensors and the like on later cars. They were all plugged when it went to the machine shop and I didn't think they'd mess with them - but they were thorough and cleaned them all out for me. Now I I have to figure out the threads to plug them. I've figured out many of them, but a couple still elude me.

    On the passenger side there are two holes. One very close to the front of the block and one about 2/3 of the way back.
    They're about M10 size, but neither a 1.50 or 1.75 fits. 3/8 is too small. 1/2 is too big. Its also not 1/8 pipe. Anybody know what these are?

    I read elsewhere that the rear one (1" above the oil pan under the rear most freeze plug) is an oil passage, and that it should be 1/8 pipe - but that doesn't work. If anyone can confirm that's what it is I'll run a tap in there and clean it up - just don't want to make a mess if its something else.

    On the top, at the back is another hole. Its either under or behind the intake. I think it might fall behind. Its close to m12 size, but m12 1.75 doesn't thread in well. Its also not 1/2 pipe, 3/8 pipe, 5/8 or 1/2 inch. Again, any ideas what this is? Again, I can tap it if its just dirty, but I don't want to screw anything up.

    Thanks!
    Scott

  • #2
    I have a '91 5.0 block at home and will check tonight for you. Are you sure they all need to be plugged? If I remember correctly, the top rear hole you have pictured is left open on mine. Same for the back lower hole where the clutch pivot would have been on an older block. Did you check them with a pick?
    1965 Poppy Red Three Peddle - Built Not Bought!
    347 Stock Block Pump Gas Street /Strip 10.49 @ 125.35

    2005 Torch Red Topless Three Peddle - 12 valve Monster
    244 Stock Block Pump Gas Street /Street Much Slower

    Current CI Count - 95

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    • #3
      The top one you can see a boss that goes into the block underneath it. The sides, I think they're going into oil passages. I'd sure rather plug them than gamble after I've installed by starting it up...

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      • #4
        First off, if dealing with an American made 5.0, you need to get your head out of the metric mode and into SAE/Imperial!
        >The first pic of the front right side should be 7/16-14 and is commonly used as the main electrical ground from the battery and alternator wiring harness.

        >>The second pic just below the freeze plug should be either 5/16-18 or 3/8-16 and may be used for a strap to secure the cable running to the starter. I believe it's a blind hole that doesn't make it to the inside of the engine. It may also be, depending on year, another 7/16-14.

        >>>Third pic, behind the intake, I believe is a threaded hole that simply opens into the space between the flywheel and block. I've seen it on some blocks and not on others and not sure of it's purpose. Stick a wire in it to determine if it actually goes anywhere important, or not. Should likely be, again 5/16-78 or 3/8-16. Given that you say it may go into a boss, it may be a pipe thread1/8" or 3/16".

        None of these, with the possible exception of behind the intake, should be any kind of pipe thread. FWIW, 7/16-14 is an oddball/unusual size, in that a 3/8-16 almost seems to "sort of" fit, but not really!

        Hope This Helps,
        Gene
        To quote my big brother: "Gettin' Old Ain't For Sissies"
        '68 coupe/5.0/T5
        '69 F250
        '56 Chebbie 3200 P/U
        '03 Miata (wife's ride)

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        • #5
          Thanks Gene. I'm headed to the hardware store now to scare up some fasteners. I'll confirm what I find. You're right about 3/6 being really close but not quite!

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          • #6
            Top back is a 1/2-13 and you're right, it doesn't go anywhere. Somewhere I read that it might be for a knock sensor for van applications.

            The one on the side under the last freeze plug takes a lot of wire. I've read its in an oil passage. Its a 7/16-14

            The front one I don't think goes anywhere, it too is a 7/16-14.

            Thanks so much for your help.

            Scott

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            • #7
              Wish you had of asked this last week when I had my engine out, I could have looked at it real easy. Glad you got it figured out.
              ----1999 F150 XLT Lariat Super Cab 4X4 5.4----
              -----1947 Lincoln Zephyr Coupe 5.0-----
              -----2000 Expedition XLT 4.6----
              " Sometimes you fix the car, sometimes the car fixes you" Steve L.

              "Do not let anyone tell you it cannot be done. No challenge can match the heart and fight and spirit of America". President Donald J. Trump

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              • #8
                Below the freeze plug, if it's like my Clevelands, and I think it is, is a drain for the water jackets for the cylinders. On mine I always install petcocks, the same you use at the bottom of radiators, to drain coolant when I need to. You could verify that by adding a little water and watching it leak out. I can't imagine it being a a oil galley, I don't know the newer 5.0 well, could it be a side dipstick hole?
                '70 Mach 1 - '72 Sprint - '94 F-150 XL -'97 E-150 - '05 Sable LS
                My Mach's restoration progress
                My Sprint's restoration progress
                "Never offer advice. Wise men don't need it, and fools won't heed it." ~ author unknown

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                • #9
                  5.0 dipstick is in the pan, so it's not that. I don't think it goes to the oil gallery either. Only place to get to the oil gallery is right above the filter. I'll see if I can see mine in the daylight tomorrow and see if it has anything in it. I'm thinking Steve has it right, block coolant drain hole.
                  ----1999 F150 XLT Lariat Super Cab 4X4 5.4----
                  -----1947 Lincoln Zephyr Coupe 5.0-----
                  -----2000 Expedition XLT 4.6----
                  " Sometimes you fix the car, sometimes the car fixes you" Steve L.

                  "Do not let anyone tell you it cannot be done. No challenge can match the heart and fight and spirit of America". President Donald J. Trump

                  Comment


                  • #10
                    Looked at mine this morning, can't see hardly anything with it in the car. Looks like a plug in it as far as I could tell.
                    ----1999 F150 XLT Lariat Super Cab 4X4 5.4----
                    -----1947 Lincoln Zephyr Coupe 5.0-----
                    -----2000 Expedition XLT 4.6----
                    " Sometimes you fix the car, sometimes the car fixes you" Steve L.

                    "Do not let anyone tell you it cannot be done. No challenge can match the heart and fight and spirit of America". President Donald J. Trump

                    Comment


                    • #11
                      Originally posted by ford84stepside View Post
                      5.0 dipstick is in the pan, so it's not that. I don't think it goes to the oil gallery either. Only place to get to the oil gallery is right above the filter. I'll see if I can see mine in the daylight tomorrow and see if it has anything in it. I'm thinking Steve has it right, block coolant drain hole.
                      I've had 4, 5.0's from 1980 up and the dipstick was through the block above the oil pan flange. I've always tapped them and installed a bolt when switching the oil pans to front sump.
                      1968 Fastback
                      90 5.0 HO
                      T-5
                      Modern leather buckets
                      Front Disc
                      2001 Bullit Green

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                      • #12
                        In the red box
                        1968 Fastback
                        90 5.0 HO
                        T-5
                        Modern leather buckets
                        Front Disc
                        2001 Bullit Green

                        Comment


                        • #13
                          Yep, you're right white68. I forgot about that hole, have had some that were factory [?] plugged with a push in plug like a freeze plug.
                          ----1999 F150 XLT Lariat Super Cab 4X4 5.4----
                          -----1947 Lincoln Zephyr Coupe 5.0-----
                          -----2000 Expedition XLT 4.6----
                          " Sometimes you fix the car, sometimes the car fixes you" Steve L.

                          "Do not let anyone tell you it cannot be done. No challenge can match the heart and fight and spirit of America". President Donald J. Trump

                          Comment


                          • #14
                            white68stang & ford84stepside,
                            I believe the hole avu3 is talking about is in a similar location on the other (passenger) side of the block. As far as being a coolant drain for the block, I don't think so. The 5.0 blocks have a drain near the front of the passenger side and near the rear on the driver side. Whatever that hole is, it certainly won't hurt anything to find the proper thread, and use a pipe thread plug or proper sized bolt to plug it. If not threaded, the right size push in plug would do!
                            Just Sayin'
                            Gene
                            To quote my big brother: "Gettin' Old Ain't For Sissies"
                            '68 coupe/5.0/T5
                            '69 F250
                            '56 Chebbie 3200 P/U
                            '03 Miata (wife's ride)

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