If you are having trouble with your copper head gasket you might try copper coat. I mentioned to a good friend, who has been building race engines for motorcycles for 30 some years, that I was having trouble getting my head to seal. He said he has always used copper coat on copper gaskets. So I used the stuff on the gasket this go round and its brilliant. Its a copper powder suspended in a light film in a spray bottle. Its supposed to lay up on the gasket and then when you tighten down it seals into any gaps and nooks in the mating surface. Just hang the gasket on a wire and give it a light coat, wait 30 seconds and do another. Do this 4 or 5 times and your good to go. Surely someone else has tried this.

email (option): micran1234@yahoo.com

Both head and barrel should be examined during a rebuild before fitting the gasket. Check with a parallel bar or any suitable 'straight edge' that the surfaces are flat. Also check that there is no face damage, such as deep scratches that 'bridge' the gasket seat.
Flatness of the head in particular should be checked carefully if an aluminium head is being fitted as these are more prone to distortion than the iron ones.
The head can be skimmed as required to produce a flat surface...010"~.015" is usually sufficient.
Likewise with the barrel but take the minimum possible off the top face to give a clean, flat gasket face...The area round the valves is not particularly important, only where the gasket sits. Material removal from the barrel should be minimal due to the fact that if too much is removed there are implications with piston to head clearance. Again .010"~.015" will usually do it. 'Squish' clearance between the piston and cylinder head at TDC (with the gasket fitted)should not be less than .025"~.030" but not more than .040" after completion of the work for the 'squish' area to function as intended but without any risk of the piston contacting the head when running due to crankshaft 'flex'..It should be noted standard engines frequently have too much clearance and this figure is worth checking as a matter of course..An excessive clearance increases the tendency towards 'pinking' or 'pre ignition'. An extra cylinder base gasket or a thicker head gasket will get you out of trouble if piston to head clearance is insufficient.
One of the features of the standard 'composite' gasket that I particularly dislike is that it makes it virtually imossible to check and maintain the correct squish clearance due to the variable amount of 'crush' from gasket to gasket when they are fitted.
Whilst I agree the application of sealants will 'get you away' if there are some problems with the surfaces a correctly annealed solid copper gasket will seal perfectly onto good surfaces and no sealant is required.
K Model Harley Davidsons for instance (the racing sidevalves) didn't even have a gasket..a single application of Aluminium paint was all that was needed to seal the machined surfaces.
It is also worth checking the alignment of the cylinder head bolts and the gasket...if any of the gasket holes are slightly out of position and are contacted by the thread of the bolts as they are screwed in this can throw up a burr on the gasket which prevents the head, gasket and cylinder contacting perfectly around the hole when tightened down. Place the gasket and cylinder head onto the barrel and screw in all the bolts about halfway...then remove everything and examine the gasket for signs of contact around the edges of the holes. If any contact is apparent open out the hole slightly with a smooth file as appropriate...Ian

email (option): ian@wright52.plus.com

Copper Coat is great stuff!

However, as we all know, the flatter the surfaces, the better the seal. A trick I have used successfully is to glide the mating parts on glass with an appropriate valve lapping compound.

This is slow and tedious, but when sitting in fromt of the telly not bad at all.

Mike, Congrats on getting your bike to run!

email (option): britool51@htmail.com

Yeah I checked my head and barrel on a surface plate. it was near perfect. What I found was the exhaust side area on the barrel where the gasket touches was thin. Not much area to squeeze between the head. Hard to explain. Copper coat sealed it. Copper coat isnt really messy or noticeable either. It isnt the same as trying to glue it shut with gasket maker. its more of a treatment. If you are able to seal your head without it that's good. But if you are having trouble its good stuff.

email (option): micran1234@yahoo.com

Be clear..I'm not knocking it....but conversely I wanted to point out that it isn't absolutely necessary to use any type of sealant and to detail how that can be done should anyone wish to.. It also provided an opportunity to run through a few other points of general interest related to the subject...Ian

email (option): ian@wright52.plus.com

Yes I'm with you Ian. Definitely the right course is to pursue sealing without the use of a sealant. I think that should be the first step. I was just saying that if you have a little spot you just cant seal or don't want to bother with decking or fly cutting the surfaces... you can try copper coat. Just another option. I wouldn't go so far as to consider it a bodge though. It really is nothing like a tube of sealant. You can't really tell its there (until you remove the head)

email (option): micran1234@yahoo.com

I googled 'coppercoat gasket sealant' and got some queries and some forum discussion about it on American 'Muscle Car ' forums but no supplier...do you have details of an internet supplier?...I'm always interested in something new (to me!) that may be useful...Ian

email (option): ian@wright52.plus.com

http://www.summitracing.com/parts/SCE-G1612/ There you go Ian.

Its primary use is when an extreme seal is required on a liquid cooled engine. An uncoated copper head gasket doesn't seal the liquid coolant very well. With that being said a good friend that builds motorcycle race engines uses it on all his engines (mostly air cooled) he said even though he fly cuts and gets his mating surfaces perfect, copper coat is that extra step to insure no problems when running very high compression. While I don't think its a must on our M20's, it surely goes that extra step to really seal tight. It is primarily used in high performance engines though. Which isn't quite the class id put the m20 in.

email (option): micran1234@yahoo.com

i though a sofened copper gasket would squeeze up and take up the different surfaces

It does to some degree. I annealed my gasket and then scrubbed it with steel wool, then sprayed it with copper coat.

Annealed copper is pretty soft, but soft is relative to something like aluminum or steel. It still isnt exactly rubber or jelly. When I removed my gasket (which I previously annealed and re installed after checking my head)I expected to see the outline of the mating surface. I in fact did not find this. I know that the thermal expansion when warm also helps seal the head. Again if you're having no trouble with your gasket then by no means should you bother with copper coat. I just find that if you have any weepage or really just want to be assured a good seal the first time... might try copper coat. It seems as though it isnt very common in the UK. I have known about it for years and actually used it. Why I never thought to try it until now is beyond me. My friend (who I used to help build engines) pointed it out. Worked great for me. Again I will stress that it isnt anything like a gasket sealant or goopy glue you might have in mind. Its a very thin copper film. it almost looks like copper spray paint. it dries with a very light tackiness, yet it isnt sticky in the sense that it gets all over things and leaves a mess. You can pull the gasket off over and over again if you lay it down wrong. I quite like my experience with it and I hate using goops and sealants to bodge a job I could do correctly.

email (option): micran1234@yahoo.com

Hi Michael..Thanks for the info...I am interested in this product for potential use in my M20 sprinter (when I eventually get to that point!).
I am planning to have both cylinder and head surface ground and to dispense with the head gasket all together, as in the K Model Harleys. These used a single application of aluminium paint to make the seal.
Removing the 'variability' possible in the thickness of an annealed copper head gasket then allows the 'squish' area to be held accurately to the absolute minmum possible...a desirable feature in a tuned sidevalve. So I am looking at this as a possibly more effective and less messy aluminium paint substitute.
The benefits for application to a conventional engine if machining facilities are not to hand might also come in useful!....Ian

email (option): ian@wright52.plus.com