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216 chevy water-pump reassembly (back to basics)

Discussion in 'The Hokey Ass Message Board' started by Chevy48, Nov 22, 2011.

  1. Chevy48
    Joined: Oct 12, 2011
    Posts: 201

    Chevy48
    Member

    Just when I thought I was starting to think I could promote myself from the dummy squad, I find I’m back at the 5 yard line. :eek:

    How can I have so many questions about something so simple? Dam it, it’s a water-pump for crying-out-loud, how hard can that be to replace?

    I purchased a NOS dealer replacement water-pump for my 216 chevy engine core that I sent off to be rebuilt. I thought I would try to replace most of the accessory items like carb, fuel-pump ...etc with new stuff. When I received the NOS pump it is a beauty! Trouble is, it does not include the back-plate. So I removed the back-plate from the old water-pump (as I don’t see any alternative) and I also purchased the two new gaskets to re-assemble and mount the pump assembly.

    The water-pump has a a back-plate with ports that mounts to the water-pump itself with two “specialized” tapered flat-head screws. A gasket goes between them. The completed unit is then mounted to the block with another gasket and four standard hex-head bolts. (See sketch below)

    No biggie right?

    Well the “old” back-plate I’m forced to use is really rusted up. I cleaned it up as much as possible, and made sure the gasket areas are especially clean. But still, some of the plate gasket areas are heavily pitted. Also, the specialized screw slots on the plate fasteners are a bit mangled as I had to use an impact screwdriver to get them out. (I believe I can still use them - as the tightening side of the slot are still fine.) But still, I find another issue, The water-pump I replaced allowed full access through the ports. The new water-pump appears to cut off one of the ports by about 30-40%. It is as if they eliminated one the machining operations on the casting?

    I certainly don’t want to go through all this and have a water-pump leak, or find out I will have restricted water flow and overheating problems?

    Questions:

    1. I was always taught to use gasket cement on only one side of a gasket. (Coat the gasket, then the metal, wait until it is tacky, then assemble.) I this true? I read somewhere that others have use silicon Red not Blue on the other side of the gasket where there is pitting? Some say if you have to use silicon, it will just leak eventually anyway?

    2. It seems I should wait until I have the rebuilt-engine before assembling anything as there is only two fasteners used on one side of the plate possibly causing it not seal well enough on the far side. If I assemble it all at once, the bolts that hold it to the block will squeeze it all together evenly before the cement totally dries?

    3. The restricted port (marked in white in the photo) shows where the casting is normally machined away to allow full-flow through the now somewhat restricted port. Is this flow loss a potential issue? Should I have someone machine it out? Or it don’t matter? Splitting hairs?

    4. I visited the local hardware store looking for some new flat-head-slotted-screws. Come to find out the ones used to hold the back-plate to the pump casting are special? Although the thread size and head diameter is standard, they are about 1/8” shorter, and where the taper meets the thread it is squared off, apparently to prevent the taper from digging into the casting.

    Also, on the back-plate where the flat-headed screw ends up flush, there are grooves marked to indicated (apparently) where the screw-slot lines up when fully tightened. They were lined up before I took it apart.

    Is there a special name for this type of screw? Where can I find new ones? Should I make sure the screw-slots line up with the marks?

    My Dad always said, "The first step in learning is to have the guts to admit you simply don't know".

    Well I just don't know....any help will be greatly appreciated.

    Thanks!
     

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    Last edited: Nov 22, 2011
  2. fordcragar
    Joined: Dec 28, 2005
    Posts: 3,198

    fordcragar
    Member
    from Yakima WA.

    What does the old pump look like in the area, that you said wasn't machined? If the old one was machined out, if it were mine I'd probably grab a rotary grinder and make it look like the old one. As far as the back plate, I'd clean it up the best that you can and seal it (I typically use the blue RTV Sealant for something like that). The countersunk screw probably isn't anything special, other than flush on the back side when everything is assembled.
     
  3. Chevy48
    Joined: Oct 12, 2011
    Posts: 201

    Chevy48
    Member

    In the old pump the area is machined away. I suppose I could use a grinder, however to really match the old pump, it will need to be milled, as it is cut all the way to the bottom.

    OK then blue-silicon is what I will use.


    Thanks!
     

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