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Copper cylinder head gasket


Having blown out several composite gaskets, I intend going back to copper (even if there is oil seepage!).  What is the optimum thickness for use with an iron head Dominator 88? .  I have seen from 1 to 5mm. advertised?  The aim is not to decrease compression, just fed up with removing the head! (and yes, the head is tightened down, at 50, and 500 miles after fitting).  Suggestions gratefully received.


If you go above 2mm of thickness then there are likely to be issues with valve clearance.

You will also find trying to anneal a thick copper gasket evenly quite difficult. If you under-heat the gasket then it won't soften enough all over and the combination of hard and soft spots will lead to seepage. If you overcook solid copper gaskets then the thinner sections around the bolt holes will vapourise and go thin and leak. I had an RGM solid copper gasket which I tried on three different engines and each one blew oil sideways.

Possible reasons that your composite gaskets dying so quickly...........There are lots of dodgy cheapo versions on the market which split as soon as you torque them down..........The head bolts on your engine may be a fraction too long and are bottoming out before clamping the gasket. You get a similar problem with rubbish collecting at the bottom of the barrel bolt holes. Especially rusty iron barrels that are 60 plus years old.

I suggest obtaining a quality Cylinder Head gasket from a known dealer and then checking all the chunks that hold the head in place. Add a thin washer tor each head bolt as a means of preventing them from bottoming out.


Its a choice between the oil tightness of the composite but with a low rate of failure but the failure being catastrophic ie cannot continue except on a recovery truck, or a higher risk failure with copper but that being a slow oil leak and the ability to continue. 

Can't comment on the right thickness but with a copper head gasket it pays to use copper wire or silk thread around the known leak points coated in a sealant.

There are other tricks like using a copper spray or a silver paint on the gasket, other option is Pliobond which is a glue and works well.

Worth a read


Thanks John Shorter for raising the subject - I feel your pain - and those responding with thoughts on a cure. Haven't suffered this problem for years but a recent build using a 'composite' (aluminium?) gasket lasted just a few hundred miles. Same torque-down method I've used for years - 650ss owned since late '70s - and all threads are sound. I like the idea of a slower failure but some further research is needed before I decide on a rebuild method. Just not this one!


I guess you have had the head and barrel mating faces checked for flatness? Pretty obvious I know, but thought I would mention it, as I had my 650SS head checked some while back, and it was badly in need of a skim. I don't like those composite gaskets, but it is holding so far since then.



There are a couple of points that need a mention with regard to skimming Norton Twin cylinder heads.

1. Most engineering shops that can offer this option generally state a minimum cut of 20 thou will take place. This may not sound much but it can really mess up the rocker angle and valve clearance adjustment. Especially if the valves are recessed into the pockets.

2. If the barrel still has spigots then the head will end up sitting on top of these rather than the gasket. The only cure being to remove the a portion or all of the spigots or fit a massively thick solid copper gasket.


If the head is not flat then it needs attending to, and understanding the knock-on effects of such work is all part of it. My spigots were removed at the same time, as the bore is + 0.040", and they were cracked. The  barrel was also lightly skimmed, as it too was not flat. So yes, whilst attending to the head, one would also check the barrel, and reduce the height of spigots as required. 

In theory one can adjust the length of the pushrods, (which I have done) provided you can get the ends off, which are pressed on. The pushrods can then be shortened to suit, before pressing the ends back on. Or, you can buy over-length pushrods with only one end installed, allowing you to cut them to length before pressing the end on. They are the tubular steel ones though, and very heavy, so a last resort, in my view.



Follow up:-  After fitting a copper gasket, I have just returned from the Spanish Teruel Rally.

Over 400 mile of hard riding ( on my ´54 Dominator ), keeping up with Commandos.  The faintest hint of oil weeping from the head.   No more composite gaskets for me!


I have seen people talk about "annealing" copper gaskets (or anything metallic) by heating then quenching. DON'T DO IT!  That is "tempering".  Anyone who has done a bit of metalwork knows that you need to allow it to cool down as slowly as possible to normalise the stresses and soften the metal.


David......I think your point above re. annealing is worth including in the DTDs. Either as part of Chapter 7 or perhaps as a separate appendix dealing with gaskets/seals???

In reply to by lionel_yexley


Some Non ferrous and exotic metals can be quenched, see quote below.

In the cases of coppersteelsilver, and brass, this process is performed by heating the material (generally until glowing) for a while and then slowly letting it cool to room temperature in still air. Copper, silver[1] and brass can be cooled slowly in air, or quickly by quenching in water, unlike ferrous metals, such as steel, which must be cooled slowly to anneal. In this fashion, the metal is softened and prepared for further work such as shaping, stamping, or forming.


Right were do I start with this  Well Most head gaskets I have come across ether do not fit right or are  total rubbish  the biggest down fall is cutting off the spigots engineers better that you or me had them put there for a reason    and I find  fitting a solid copper gasket over the barrel  first for this fit and try the bolts fittings as well before any other fitting   you may find some of the stud holes are not big enough  or the cylinder holes rides the spigots  so you need to file some of this off to make a good fit, And clean out all stud and bolt holes and clean all their threads too,And make sure no threads are damaged,  Do keep every thing Clean clean clean!!!    Then I use  Stag Wellseal on both side by using a artist brush to apply now alow to dry a bit  go for a bacon and tom butty and a cupper tea , by the time you get back  then you can fit the push rods and the then head  start with the center nut and work out,  and nip up every one then in stages  toque up each nut and bolt  by starting at 10lb  now all 5/16ths nuts are 25lb and all 3/8th bolts are 35lb  starting from the center out  doing it this way I have never had any blown gaskets  in the last 45 years of owning Nortons   now have fun out there  yours  anna J


Anna.....I think quite a lot of owners will be disagreeing with those torque setting numbers. In my experience anything above 20 ft lbs on the two front barrel 5/16" studs leads to stripped threads.

Plus I certainly would not apply 35 ft lbs to the 3/8" studs that drop down from the cylinder head. The Aluminium is quite soft and they will pull out.

In reply to by philip_hannam


hello  phil  well you try telling this to Haynes  Manuel,s  not me,    yours anna j 


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