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MG Midget and Sprite Technical - Exhaust gasket material choices.

Are there any experts on the subject of gasket material choice?

For a odd-ball project I need to get some gaskets made and wondered what material to use. Copper or Graphite? If Copper, can it just be plain sheet or does anything need to be done to it? Where can it be bought from (UK)?

Any tips would be gratefully received.

Rob
r thomas

Rob-
Hard to say without more info, then still hard!
"Copper" is a possibility, if you mean plain copper. Easy from roofers, metal supply etc. Won't fill large irregularities and must be full annealed.

"Graphite" is a meaningless term without more info re the particular material. I know of some "graphite" packings, expensive and special generally. There are steam pipe packings available as sheet, but they usually will not take exhaust temps for long.
Thin stainless in soft temper is a possibility, especially if you are a clever lad. I can tell you how to put sealing ridges in this or copper sheet, not trivial but doable.

What are the materials, surfaces and location? Sometime no gasket or a silicate sealer is best. The typical exhaust gasket was asbestos between metal sheets, and you can duplicate that with asbestos replacement material in sheet form, including high temp ceramic fibre mat. = mucho shekelo!
Many of the asbestos replacements are worthless, and so are supplied gaskets made from them.

FRM
FR Millmore

On the shelf I found some Klinger Mark 100 which seems to be white asbestos impregnated sheet. It shows 510 centigrade on the label. The cheapest manufactured gasket found so far is going to be about £100 ($150 US) so I'm willing to try other options.

The engine it is going in isn't far removed from an 803cc A-series, albeit with less power and it is 30 years older.

r thomas

car or aeroplane?
(just thinking about the consequences of failure)
David Smith

Rob,

I could supply you with some 1400C refractory ceramic fibre, 1260C Superwool HT body soluble fibre, and Sairset refractory mortar that rated to 1700C if you want to try them. The Sairset once heated will go off as hard as a rock. Maybe make a mat of the fibre and Sairset and place it in the join and run the engine to cure it.
David Billington

Rob,

Try Ram gaskets in Redruth for graphite sheet.

Have a good web site.

R.
richard boobier

It is for an expensive vintage Morris so failure is more critical than for an aero engine. :o)

I've asked various companies (inc RAM Gaskets) for their advice but haven't had anything useful back, yet. I'd guess that anything that works for a Spridget will work perfectly for the Morris. I just wasn't sure if the gasket material for the Spridget was anything special or had any particular property that made it work. If the asbestos stuff here is designed to work up to 510c and exhaust gasses run at maybe 800c then there must be some cooling going on betwen cylinder and manifold. In the same way, an alloy head works with 800c gasses when the alloy melts at 650c. How come???

David B. Thanks for the offer. At the very least it would certainly not melt!!!
r thomas

Rob,

I know a number of warm and hot glass workers so I should also be able to scrounge a bit of fibre paper in various thicknesses. It would normally see service to 800C and above so should be OK temp wise in the application.

Regarding your question about 650C melting of Al and 800C exhaust it is down to thermodynamics. The heat exchange from the exhaust gases to the cylinder head not being great enough to heat the metal to a troublesome temperature with the heat taken out by the coolant on the other side. That having been said a mate works in engine development and has said that often considerable work is done to keep the exhaust side of the cylinder head down to an acceptable level, IIRC around 200C as much above that that head material starts to lose its properties.
David Billington

As David says. I have seen a lot of trouble with nonasbestos gaskets since asbestos was declared a "bad guy", but the problem has decreased in recent years. Big thing with Loose fibre materials is the hot gases nibbling of the edges. I have made thimbles to surround the hot holes, from thin aluminum, copper and stainless, Metalworker's art, which I think you like - bulletproof.
Rover used asbestos filled copper o'rings in grooves around the ports on the TC.

FRM
FR Millmore

David. Thanks. That would certainly help. At the very least I'd welcome the name of a supplier. A Klinger agent says they can sell me 1m x 1m sheets for about £100 but that seems overkill

FRM. Is there any special technique for the rings? Do you need to thin the paper round the edge or just add the thin sheet and bend the ring round the edges?
r thomas

Use a full annealed sheet, thin, less than .010 usually, .004-6 is good with copper. You can buy very heavy foil of this range in art/craft stores, kids do pictures etc with a pointed wood stick in aluminum, copper, brass, or you can get SS tool wrap used for heat treating tools without scaling - .002 and very soft but tough. All these cut very nicely with a sharp scissors - don't let the lady catch you with her needlework tools! A sort of big washer about 1/4 wide, extending 3/32 outside the hole on one side. Or, you can use the metal over the whole gasket on one or both sides just like OEM, Trim one side to the hole and the other about 1/8 overhang. Then you can push the centre down with your fingers or a piece of rod to go through the hole and spread out on the other side. Various tapered point mandrels can give a very nice round and tight turning of the edge down the hole.
No reason to thin the filling; this gives best sealing at the hole, where you need it.

I make heatshields with the same technique, but .040-.060 sheet and 1/16-1/8 asbestos.

FRM
FR Millmore

Rob,

Drop me an email at djb(at)metal-arts(dot)co(dot)uk as I have all the materials including SS tool wrap foil and can let you have a bit. For suppliers that might do small quantities you could try pottery suppliers such as http://www.bathpotters.co.uk/ for fibre materials or people like http://www.warm-glass.co.uk/ for fibre paper etc. SS Tool wrap foil I got from http://www.knight-group.co.uk/ but it's spendy.
David Billington

This thread was discussed between 26/07/2012 and 27/07/2012

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