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die filer update --RTV prep cleaner

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  • die filer update --RTV prep cleaner

    Thanks to all for all for the help. The new bearings are in and I have to use some stock oil seals since the Keller Co. didn't call me back. The upper oil seal was installed above the blower hole and the shaft was installed higher so the blower piston didn't hit the seal. Not sure how it was supposed to look?

    Was it supposed to have a seal on the top shaft?

    RTV was suggested to be used as gasket sealer--what would be the best prep cleaner to use before re-assembly that is compatible with RTV?

    It is really hard to get the mating surfaces clean enough. I have used scotchbrite, mineral spirits and scraping with a putty knife and they still aren't perfect. The manufacturer's mill marks are fairly rough and the pores of the cast iron are holding some dirt. Assemble anyway or further cleaning?

  • #2
    If you want to try RTV, I might suggest using a method similar to what I use to seal intake manifold ends. Except for an intake, you lay a really thick bead - depending.

    Clean the surface with brake cleaner and blow dry. Apply a thin even layer to one part - how thin depends on the sealing surface. I'd try for smooth and just barely translucent that fills the voids. Let that start to set up - 20~40 minutes. Then apply a very thin layer to the mating part. Assemble and snug the fasteners "firm", do not tighten. Let the RTV set up 24 hours, then final torque the fasteners.

    RTV in general makes a so-so gasket, depending on the application.
    Merkel, Tx


    • #3
      RTV sealer is practically useless if allowed to "set up" before assembling the parts.
      The correct way to use it is to clean everything with a brake parts cleaner (not carb cleaner) and apply a thin bead of the sealer to one of the mating surfaces. Then, press the parts together and torque them to their final value.
      RTV has a "Skin over" time of 8 minutes, so you want to get everything in place and secure before the bead skins over.

      The thing most people don't know about RTV sealers is the fact that it was designed by the 3M company and Dow-Corning as a "Formed-in-place" gasket.
      Which means, simply, that the parts to be sealed should be in their final positions before the sealer starts to cure.

      Many times, I've seen a nice fat "worm" of RTV on an intake manifold split wide open when the manifold was set in place, all because the guy doing the job let it "skin over" first. RTV cures from the outside in. So it will split open if squeezed, once the skin has formed.
      Assembling the parts with the sealer "wet" will not cause a torque or dimensional change in the assembly.

      RTV sealer is actually a great sealer if used properly.

      This isn't an opinion, it's right from 3M and Dow-Corning
      No good deed goes unpunished.


      • #4
        I think that these things are notorious for leaking. The mating surfaces are just flat surfaces with no grooves and they have lots of vibration. When I took it apart, there were no gaskets, just some dried liquid gasket goop.

        Someone here and my friend at the Auto supply store suggested RTV rather than formagasket.


        • #5
          Mikem, if the original fit did not have a gasket, I would not use RTV. Use something tacky like the aviation stuff, I think Permatex used to have a variety of it. I have had good luck with RTV if there is room for a gasket and you snug it down on assembly and come back later and torque it on down. I have pulled rocker covers where the previous installer had squeezed about all of the RTV out of the joint resulting in leaks.


          • #6
            See here (what Saltmine said):


            I love this stuff. It seals really well. I have even used the copper grade stuff to make a cylinder head gasket for go-kart engines. This material will fill voids and rough surfaces very nicely. I would use acetone to clean as much oil from the pores of the cast iron as possible and scrape the old stuff off as best I could and call it good enough. I've found it to be very forgiving.

            I've got oodles of copper and ultra gray lying around. I use it for practically everything and it hasn't failed me yet.


            • #7
              Never had the "split open" problem - I don't let it skin hard, just get some backbone to it. Otherwise it just oozes everywhere. The trick on the intake is to not get the bead too big, just right depending on the gap. But that's with any of it - too little, no seal - too much, big mess or worse. In a hot engine it become plastic and will wreck havoc on the oil pan screen. I love watching people empty half a tube on a valve cover flange. RTV wet acts more like a grease than anything. Grease up a gasket good with it, torque the parts and watch the gasket slide right out from between the parts.

              In my experience - the permatex stuff I find in the parts stores is still goopy even after about 20 minutes, never seen one skin in 8. Maybe in 100F ambient, never tried it. I use the RTV in place of the cork end seals in my performance engines mainly due to variances caused by decking blocks, heads, etc - if done right they never leak and they don't ooze into the engine. I use almost none on an engine other than the manifold end seals. Works for water pump gaskets - coat the gasket thin, install, torque light then full after some setting time. When you have to pull the pump, the gasket will peel right off the motor. However, if the sealing surfaces are in good shape you really should not need sealer.
              Last edited by Falcon67; 07-29-2009, 05:44 PM.
              Merkel, Tx


              • #8
                I have had very good luck with Permatex "The Right Stuff". I had a couple of leaks in my mill enclosure and well as around some coolant tank fittings and it has survived that for several years now. It seems to hold up well to Vactra and coolant.


                • #9
                  Bought some Permatex black RTV and used that. It needs to cure 'til tomorrow night so then I'll try to start to put it back together and report back. Thanks to all--Mike.


                  • #10
                    Yup, I like RTV. I like the copper, even for parts that arent gonna get hot. I dry both surfaces with acetone, lay a bead, not to big. Mate the parts up quick so no skin has formed and bolt up till I have a good squish around the entire seam. Not to final torque specs, just shy, so there is maybe a 32nd of an inch space. Then let her sit, the longer the better. Three, four, hell, seven days. RTV cant be rushed. After that I torque it down.

                    Never had any problems with that method. The key is to let it sit before final torquing to let the soft core harden so it doesnt squish out. And to get both surfaces on wet silicon, oops, RTV so they seal. So now you have a chemical seal (wet RTV on dry metal) and a mechanical seal (cured RTV being compressed) JR
                    My old yahoo group. Bridgeport Mill Group



                    • #11
                      The RTV is cured for the lower crankcase to base seam. Tonight I will reassemble it enough to see how it runs.

                      The vertical shaft that has the jaws that hold the files has a lot of wear where it went though the upper sleeve bearing. It must have been run for long time after the oil leaked out. It is almost like a notch in one place and tapers back to full size over about 2.5 inches. I replaced all the bearings and smoothed and polished out the shaft. If it still "clunks" when it runs, I may have to replace the shaft.