Copper Head Gasket

You could try lapping the head, time consuming and messy but seems to work, and/ or try using high temp silicone (permatex etc) particularly as there is no pressure to speak of. it holds the joint between the expansion chamber and barrel oil tight on my 2 strokes so should be up to the job.

I managed to fix a similar persistentleaking iron head problem by replacing the aluminium gasket with a new copper gasket cutfrom a piece of copper sheet taken from my oldhot water heater tank.(.023" thick). I annealed it then gave it a thin coating both sidesof Loctite 510 high temp flange sealant.

G'day John, I sharpened up aHSdrill to cut sheet metal then, with a block of wood underneath the copper, slowly cut the hole with a reasonable bit of pressure on the drill press, then the drill simply punched through the last bit. The two smalldrain holes drilled with a standard HS drillusing a drill brace. Cut the centre hole with curved tin snips, with a final dress with a half round file.

I have had it off several times and any remains of the Loctite burns off in the re-annealing process.

Another thought, if the leaking oil is very sooty black, it maybe coming from the combustion chamber, as the gasket stud hole is very close to the bore.....I have, unfortunately, experienced this also. Loctite fixed all the weeps/leaks.

Paul

Hi John,

Dan's suggestion is of grinding the head is the correct way to go. Head gaskets are fine for multi cylinder and side-valves engines but if you have aspigot joint, fitting a gasket completely takes away the concept of the double face joint. Nortons used to grind these joints back in the vintage days but this is a time consuming operation and as the level of production rose they opted for the easy option of fitting a gasket. As an example, no Inters or Manx were fitted with a head gasket. If you fit a gasket of say .020" then you have that gap between the inner spigot joint. This joint is the first barrier of the seal and this is lost with a gasket. This small gap also disrupts the combustion process and at around 250psi explosive pressure will eventually reach andaffect the gasket.

Valve grinding paste is best used for grinding the 2 faces until you have an even ground surface on all surfaces. I always find it is better to have the barrel on the bench and oscillate the head onto it. The paste can get a bit tacky as you grind, so a splash of petrol will help. Make sure you clean every trace of paste offespecially if any gets into the drain holes. A non hardening sealer should be thinly spread on all 4 surfaces and allowed to dry for a fewminutes before bolting down. I usually torque down to 50 ft/lb and all of this has worked for me with up to 12 to 1 compression ratios.

Other things to checkare the quantity of oil getting up to the rocker box and if the crankcase breathers are clear and not causing excessive pressure.

Regards, Richard.

Interesting reading Richard, but how do you address the problem John has re the oil leaking from the two fore and aft drain holes from the over head valvegear on the '52 iron head?

Hi John/Paul,

Sorry if I didn't make my reply more informed, I was nodding off while typing! I think John's engine must have some distortion between the head and barrel as 300/400 miles is about how long the hot oil would take to dissolve any sealant if there was any gaps, however small. By lapping-in the faces and using a thin coating of sealant the full pressure of the of the head bolts is focussed on both faces and should be oil-tight around the drain holes. By using a gasket on only the outer joint you are allowing heat and pressure to cause problems. Counter-boring the barrel for "O" rings or fibre washers is fairly easy if you have a pillar drill, but make sure if you use "O" rings they will stand the heat and oil with-out failing.

On these engines the banjo oil feed is connected to the rocker box by the largehollow bolt which controls the flow by having 2 holes about1/16"diameter, make sure no one has made these bigger as this will be too much oil. Another thing to check is the head bolts, as the ones fitted are blind sleeves, which is not a good design. On later engines these are bored right through. Make sure the thread is free and there is no debris jammed in them. If you read the contemporary road tests there was usually an oil leak somewhere, even when they were new!

Regards, Richard.

These are the words from George Cohen

The goal is to obtain a double joint with the spigot of the barrel mating in itsrecess .For Iron head and barrels, there is rarely any distortion and the easiest way to obtain a good joint is as follows: Hold the cylinder head upside down in the vice (securely but without causing any damage). Put some coarse grinding paste on the broad surface and fine in the spigot recess and add a few drops of thin oil to both. Carefully fit the barrel onto the head and withaanti-clockwise and then clockwise rotating motion, lap the two together. After a few minutes, wash of all the paste and oil and inspect. You should be able to see the lapping on all surfaces. Repeat until a perfect face on both broad surfaces and spigot are established.

Torque Iron set ups to 45 ft/lb and aluminium one to 32 ft/lb. You can use a very slight smear of either a hard settinggoopor even a smear of oil or grease, which will burn hard.

Hey Presto, no more oil leaks.

http://www.norton.uk.com/expert.htm

Dan

Mine had signs of being lapped previously, so isn't a good comparison but was pretty close. When I saw George, he said that sometimes they need machining to bring them within a few thou. He was going to do mine for me, but the application of some engineers blue showed it wasn't far out and half an hour's lapping had a dull grey finish to both surfaces.

One suggestion I'd make is block the oil drain holes with candle wax, it took longer to clean up the mess than doing the lapping!

Not wanting to disprove anyone, but I just notice in my spares list for the '50's iron heads, a cylinder head gasket. I guess this is why they are included in the complete engine gasket set.

Reading from my Norton book, by E.M.Franks, he states that post war O.H.V. engines were fitted with a head gasket in 1946, to dispense with the head lapping to achieve a gas seal. In 1948 the O.H.V. and side valve engines were completely redesigned withthe overhead rockersbeing oil fed through an external pipe from the pump return and then returning to the crank case down the push rod tubes with the excess drainingdownvia two drilled holes in the barrel.

So, going by Mr. E.M.Franks, post war engines were not designed to have the head lapped.

Hi John/Paul,

Just feel I need to add some historical info. Edgar Franks was one of Norton's designers back in the '20s and undertook the modernisation of the ohv/sv range for 1931. The fitting of the head gasket in 1946 was purely a cost cutting measure as the engine was exactly the same as the 1939 version. Doug Hele redesigned the engines for 1948, and it was nearly his un-doing as a designer. This was due to changing the cam followers from lever type to REVOLVING mushroom ones. This seemed the right way to go, but what the road testers reported back was noisy engines and lack of performance. When the engines were stripped it was found the cams had worn through at their highest point in less than 1,000 miles. Unfortunately machines had already been sold to the general public and this proved costly in warranty claims. This is why all subsequent followers were NON-revolving as it was the cheapest method of curing the problem and carried on to the end of production in 1963. I don't think Doug Hele specifically designed the engine to use a head gasket as the spigot joint has exactly the same dimensions as the 1931 engine. To sum up, what financially suited the factory was not necessarily best engineering practice.

Regards, Richard.

on the drain holes down the barrel wonder if hollow steel dowels would help inbetween the head and barrel drill the barrel dowel for a good tight fit and drill the head to suit slightly deeper and push fit so no problem mating them together then no gasket . just a theory . Baz

Agreed.

When you have a nice even finish on spigot and the wide head face, clean it all off, and then put coarse grinding paste on the wide head face, and fine paste on the spigot. Grind some more, so that the spigot stands a little taller. You want a nip of something like 1 or 2 thou so that the spigot gives a tight fire seal. Then clean it all immaculately clean

Paul

Previously richard_cornish wrote:

Hi John,

Dan's suggestion is of grinding the head is the correct way to go. ....Nortons used to grind these joints back in the vintage days but this is a time consuming operation and as the level of production rose they opted for the easy option of fitting a gasket. As an example, no Inters or Manx were fitted with a head gasket. .... Valve grinding paste is best used for grinding the 2 faces until you have an even ground surface on all surfaces. I always find it is better to have the barrel on the bench and oscillate the head onto it. ....

Regards, Richard.

If you don't want to lap the head try the copper head gasket first, much better than the aluminium in my book, and if it works fine, if it doesn't, then you can lap it?

Dan