Gaskets for small surfaces

[flavinny]

Making progress on installing a new boiler on my Allen engine but looking for suggestions on "how to".
Before starting the boiler replacement project, I had a problem with the stem on the blowdown valves leaking. I removed the valve and replaced a dried o-ring and reassembled and reinstalled the valve. It now leaked between the two halves of the valve body. The original valve had no gasket, so I initially tried some RTV rubber which did not work. The problem is that the surfaces are so narrow a traditional gasket does not seem to work, the gasket material just gets pushed out. Next option seems to be to try to lap the parts together, but I see the possibility of making things worse. I also considered using Loctite has anyone had experience trying this any other suggestions?

[hoppercar]

I use number 2 permatex on everything

[cbrew]

take a THICK piece of glass and some 2000 grid wet sand paper (used to auto painting)
using a water, likely lap the mating surfaces. use bluing to so you can see the surfaces are true.
then reassembly

[John Hasler]

Use a very thin, stiff gasket material such as printer paper. Leave a lot of overhang on the outside and trim it off after assembly.

[NP317]

What CBrew suggested.
I always lap the blowdown valve halves on a flat plate when servicing them. It is easy to see when the surfaces are shiny flat.
They always seal perfectly that way.
RussN

[Bill Shields]

Are you sure that there was not a thin copper ring on the inside?

[RET]

Hi,

CBrew is right, but instead of sandpaper, use polishing paper because it is thinner. I use 400 grit, but while it works, something finer would be better and I use it on a surface plate (because I have one). If you don't, glass is a good substitute. While it may be obvious to most, make sure the abrasive side is up.
I don't use gaskets, I use the lapping method instead and it always works. It doesn't take very long either and when you are done, you will have a mirror surface on the part.

Richard Trounce.

[cbrew]

Hi,

CBrew is right, but instead of sandpaper, use polishing paper because it is thinner. I use 400 grit, but while it works, something finer would be better and I use it on a surface plate (because I have one). If you don't, glass is a good substitute. While it may be obvious to most, make sure the abrasive side is up.
I don't use gaskets, I use the lapping method instead and it always works. It doesn't take very long either and when you are done, you will have a mirror surface on the part.

Richard Trounce.

likely just used the wrong term, i use four stages when i lapped my valves surfaces, started with 400, 800, 1500 and 2000 grit.

[Santafescotty60]

Hello Good People ,I have used glass plate, comet and diesel fuel. That is what we lapped fuel injectors on older Mercedes diesels