closing water passages

Discussion in 'Small Block Tech' started by brblx, Feb 28, 2003.

  1. brblx

    brblx clueless

    need to close off the two inner water passages on a set of later model heads (350)...don't want to shoot water into the lifter valley.

    what's the reccommended way to do this? i've though of the two things often used on heat crossovers - freeze plugs and a filler like jbweld. how well would these hold up, though? i don't need a freeze plug getting shot into my cam from the pressure.:Dou:

    you out there, jim burek? i believe i've heard you talk of doing this before.

    thanks guys.
     
  2. sbbuick

    sbbuick My driving scares people!

    I have not heard about blocking water passages, but I did block off my heat risers with JB Weld.

    I used tin foil to hold the putty until it dried, then used 3 or 4 packages of JB Weld and filled the holes until almost flush iwth the head flange. That was 11 years ago - no problems!
     
  3. brblx

    brblx clueless

    anyone else? i'd like some more opinions before i subject some jb weld to that much pressure...
     
  4. sbbuick

    sbbuick My driving scares people!

    I'm a little "clueless" about this.

    I am using a set of later heads, I believe that they are '78 vintage. The block is 71 or 72.
    I never blocked any water passages. Could you give more detail as to which passages you are referring to??
     
  5. TXGS

    TXGS Paint by numbers 70 GS 455 4spd

    on a 350 I am not aware of any changes that need to be made other than optional heat risers.
     
  6. brblx

    brblx clueless

    there are two slightly oblong holes between the middle two cylinders on the intake side. everything else is the same.

    if these holes aren't covered, coolant will dump straight into the lifter valley, it appears. seems odd, but that's what it is.

    sbbuick, if you are running an early block with late heads, i'm not quite sure how it's functioning right? :confused: maybe i'm missing something..
     
  7. brblx

    brblx clueless

    here's the best pic i have since the heads are somewhere else at the moment.
     

    Attached Files:

  8. buick535

    buick535 Well-Known Member


    There are a couple of ways to plug theses holes. First, you have to make the holes round, a die grinder makes this easy. Then what we usually do is find a freeze plug that goes in tight, we normally use a 3/4 inch plug, then we use an epoxy, j-b weld will work, but i use a titanium 2 part epoxy, I put the epoxy all around the hole , like a sealer, then hammer in the plugs a little deeper than flush, then put more epoxy around the edges.
    You can also tap the holes, after making them round and screw in some pipe plugs. This is a much more difficult way, but works very well.

    I've never had one of the freeze plugs come out. Jim Burek
     
  9. brblx

    brblx clueless

    thanks jim, that sounds like a good idea...i doubted if a filler would hold across that large surface, and i thought a freeze plug may pop out, so that sounds like a good use of the two. i think i could round them out with a dremel and the right bits pretty easily, and tap in a couple freeze plugs from the parts store.
     
  10. buick535

    buick535 Well-Known Member


    A dremel will work fine. Depending on what the hole size ends up, you can use either a 3/4 inch plug , or a 20 mm.
    These are available at places like Pep Boys. You need to plug both holes on each head.
    This is only necessary if using the later heads on the early block.. Jim Burek
     
  11. sbbuick

    sbbuick My driving scares people!



    I guess I'm just lucky! Well, no - I believe that it's possible thst the head gaskets block the holes off for you. No?
     
  12. brblx

    brblx clueless

    nope. head gasket doesn't cover it. on the intake side of the head gasket, it stops right at the edge of the cylinders and does not cover the area where the water jackets are, which actually hangs out over the block.

    you must just have a different year block/heads than you think?:Do No:
     
  13. buick535

    buick535 Well-Known Member



    The 2 holes we are referring to here are covered by the composition style head gasket, however, the early blocks , I believe 72 and older do not have the 2 scallops to support the gasket in this area, so while the gasket does cover the holes, it will not hold up to the water pressure as the engine heats up.
    These 2 holes absolutely must be plugged on I believe it's 73 and up heads if using them on a 72 and earlier block.
    Jim Burek P.A.E ENTERPRISES
     
  14. TXGS

    TXGS Paint by numbers 70 GS 455 4spd

    Thanks for all the info on the 350. I have a mid 70's 350, a 70 and a 72. Always good to learn new things thanks guys,
     
  15. sbbuick

    sbbuick My driving scares people!

    Wow, I am baffled - happily baffled, however.

    Maybe I have different heads than I think, but I know that it's a 71 or 72 block.

    The guy I got them from (in the late 1980's) said '78. The heads do not have the year cast into them like 71's and 72's do - right at the front behind where the PS pump is. I kind of hoped that they WERE 78's because I'd have the hardened valve seats.

    There is some very good info on this post. Thanks everyone!
     
  16. brblx

    brblx clueless

    well, here's my handiwork.

    i coated the edges of the plugs in jb weld and pounded them slightly below the edge of the hole. i'll go back over it and put a little more around the edges.

    i did nick the head a couple times when the dremel slipped. damned shaky hands...:Dou: that mark on the right isn't as bad as it looks, though, you can't even feel it.

    [​IMG]
     
  17. buick535

    buick535 Well-Known Member




    David, that looks fine, but I would definately do a cleanup cut on thoses heads. Jim Burek
     
  18. brblx

    brblx clueless

    they're actually pretty clean, they just still had old gasket, dust from grinding the metal, and some superficial rust in those pics. i've since cleaned them up. definately not a sparkling machined surface, but it's smooth and clean and should seal fine with a composite gasket. (in my opinion, at least, which isn't worth much:laugh: )
     

Share This Page