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Alloy or copper?

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Alloy or copper?

Posted by John Oldridge at February 11. 2018

I am in the process of re-fitting the cy head on my M50, (a very minor oil leak from the front drain hole ) and wondered if it would be better to fit a copper gasket instead of the alloy one, (for various reasons I don't want to 'lap' the head and barrel).  also someone once posted how to re-torque the head after a small interval to prevent any problems, and I can't find the post, ........any help/advise appreciated.

Regards John O

 

Re: Alloy or copper?

Posted by Dan Field at February 12. 2018

still can’t delete a duplicated post 😔

Re: Alloy or copper?

Posted by Dan Field at February 12. 2018

I run mine without a gasket, but as a rule I prefer copper, which you can anneal and reuse. The other option is to have the barrel machined to take an o ring.

Re: Alloy or copper?

Posted by John Oldridge at February 12. 2018

Cheers dan, I think I'll go the copper route. someone once posted about re-torqueing after about 100mls but  I cant find it, any help anyone?.

Next time I remove the barrel I will lap in, and fit 'O' rings,.............. is the point of contact the flange and jointing face, or just the flange?, also I guess the 'O' rings have to be able to take a lot of heat, 

Regards John O

Re: Alloy or copper?

Posted by richard_cornish at February 12. 2018

Hi John,

This is a post I sent in May 2016, it might be of some use.

 

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 a spigot 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 and affect 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 off especially 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 few minutes 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 check are the quantity of oil getting up to the rocker box and if the crankcase breathers are clear and not causing excessive pressure.

Regards, Richard.

Re: Alloy or copper?

Posted by Ian MacDougall at February 13. 2018

Agreed, the lapped joint is the way to go but for the double ground joint to work properly the height of the spigot has to be 0.001" taller than the depth of the recess in the head. This ensures that the gas tight seal is achieved on the top of the spigot. See attached sketch, courtesy Dr George Cohen. My 19S head joint is lapped but only after the head was skimmed so that the recess depth was matched to the spigot height. Mike Pemberton did that job for me, along with the oil drain o-ring mod. No more leaks from that area. George also drew attention to the possibility that heads (esp alloy) and barrels become distorted over the years so getting the relationship between spigot and recess is not always easy.

The following text is copied from George Cohen's website:

An all the single cylinder engines I have worked on (from an all iron head & barrel twenties OHV to an all alloy sixties DOHC Manx) the same principals and engineering apply.

There is NEVER a gasket. The idea is known as the “double ground joint”.

The theory is simple, the engineering a little more difficult.

The head joint comprises of two parts; the spigot interface and the wider head barrel joint. Say, the spigot on the barrel is 0.125 inch high, then the recess in the cylinder head needs to be 0.124 inch. This means that the seal is at the spigot joint and the wider joint is to prevent distortion.

The practically, especially on well used alloy top ends is a tad more difficult. If you measure the spigot height on the barrel, it is unlikely to be the same all 360 degrees around. The same applies to the wide surface on the barrel. With frequent heating and cooling over 50 years the original manufacturing tolerances have been lost and distortion has taken place. On a fifties Manx engine I worked on last year the barrel, at the wide flat surface was distorted by 0.008 inch and at the spigot, 0.005 inch. The cylinder head was worse, with the wide surface being 0.013inch off flat!

Consequently these defects need to be corrected.

Mounting the barrel in the lathe and truing up and machining is relatively easy, but the cylinder head is more difficult. A special jig has to be made up to allow the truing up to be established. A good medium size lathe, grip true facility, magnetic face plate and some clever thinking is required.

The goal is to obtain a double joint with the spigot of the barrel mating in its recess . 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 with a anti-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 setting goop or even a smear of oil or grease, which will burn hard.

Hey Presto, no more oil leaks.

Attachments

Re: Alloy or copper?

Posted by John Oldridge at February 13. 2018

O.K.Gentlemen,

Sounds like the lapped joint is the correct way to go, (with 'O' rings) My final questions:-

I assume the barrel is machined............not the head,   and where do I get the 'O' rings, I imagine they have to stand quite a bit of heat!

Regards John O 

Re: Alloy or copper?

Posted by Ian MacDougall at February 13. 2018

Hi John

Yes, a shallow pocket is machined in the barrel. I am using Viton O-rings, OD 11mm, thickness 1.65mm. I bought them from Brammer, Code is BS011VI75. Should be available on-line but I can't find them right now.

Cheers, Ian McD

PS A question for Richard: You mentioned engine breathers plural - how many are there? I am aware of the crankcase breather with ball valve that points towards the final drive chain, also the timing case breather that vents to the road. Are there any others? My timing case breather piddles excessively and I suspect excess crankcase pressure. I have tried different variations on the crankcase breather (with original ball valve, with Enfield "duckbill", without any valve) but none had any noticeable effect on the incontinence. Maybe this should be a new thread.

Re: Alloy or copper?

Posted by John Oldridge at February 13. 2018

Thanks for that Ian,

Yes there are three breathers on my M50, the two you mentioned, and another on the inside of the chaincase where it fastens to the crankcase, this is a separate alloy section that acts as a spacer, a small hole is drilled up to the bearing hole. I have filled this hole with a screw, so it doesnt drip,and fitted a long pipe to the large breather at the rear, that exits near the back numberplate, it all seems to work O.K. I dont get excesive oil escaping from any of the two pipes.

Regards John O

Re: Alloy or copper?

Posted by richard_cornish at February 13. 2018

Previously Ian MacDougall wrote:

Hi John

Yes, a shallow pocket is machined in the barrel. I am using Viton O-rings, OD 11mm, thickness 1.65mm. I bought them from Brammer, Code is BS011VI75. Should be available on-line but I can't find them right now.

Cheers, Ian McD

PS A question for Richard: You mentioned engine breathers plural - how many are there? I am aware of the crankcase breather with ball valve that points towards the final drive chain, also the timing case breather that vents to the road. Are there any others? My timing case breather piddles excessively and I suspect excess crankcase pressure. I have tried different variations on the crankcase breather (with original ball valve, with Enfield "duckbill", without any valve) but none had any noticeable effect on the incontinence. Maybe this should be a new thread.


Hi Ian,

  John is correct with his description of the breather located under the drive-side main bearing boss. The reason this hole is here is to lubricate the outer main bearing by causing an oil mist to reach the bearing by crankcase pressure through the main-shaft central boring and then escape to the road. A lot depends on how fast/hard you ride your bike. If you're happy to potter around the leaks shouldn't be to bad, but if you do lots of motorway miles or just like to crack-on, the breather with the ball valve is too restrictive and it's best to have a straight through union and pipe. If you look at Manx engines you will see an extra breather on the front of the crankcase. The breather? pipe under the mag chain cover is only a drain pipe to get rid of excess oil as any pressure can escape from the opening where the mag is, so it makes you think there was always some oil seepage. The inlet cam spindle was modified sometime around the mid '50s and these have a reverse acting scroll to try and minimise the problem. Unless you can fit a modern type seal, which will be difficult, make sure the bush and/or spindle are not excessively worn and shim any end float so there is only a small gap between wheel and bush.

Regards,  Richard.

Re: Alloy or copper?

Posted by David Cooper at Wednesday 11:31

Interesting thread here both on use of gaskets or ground joints, and O-rings.  If I remember correctly (and maybe I don't) I believe my late friend put a short steel spigot tube with O-rings each end in prepared grooves in his featherbed ES2 - but even so his bike always leaked oil down the barrel and he never found out where it came from so I've no knowledge to offer on that topic.

But do Richard's comments about drawbacks of gaskets deserve more scrutiny?  Since the vast majority of modern engines, running at far higher rpm and (in many cases I guess) pressures, do employ gaskets, that must surely say something about modern good practice?

The Late, Great George's description of preparing the joint on an old engine might have been the best way to do it - but he had both an excellent machine shop and the skills to employ it.  I suspect his idea of a 'medium size lathe' is a bit different from what most owners possess.

If I had an ES2 I might try to lap the joint - but if I could not get good contact on the proper surfaces, I'd fit a gasket rather than send it off to be machined.  So that comes back to the John's first question: copper or aluminium?  Which is better?  You can anneal both.  Does it matter?  Or was it a matter of price?  Copper used to present security problems - aluminium welding cable was widely used on the construction site I worked on in the early 70s, simply because copper theft was such a problem.

Re: Alloy or copper?

Posted by ian_soady at Wednesday 12:53

Copper is easier to anneal - just get red hot and quench or not according to taste. Aluminium doesn't change colour (yes I know you can smear it with soap but with something as big as a head gasket that's tricky) so it's easy to end up with a puddle.

As and when I take the head off my ES2 I will be trying to lap it in as I've never done that before.

Re: Alloy or copper?

Posted by Ian MacDougall at Wednesday 15:10

David,

The decision to go for a ground head joint on my 19S was frustration at not being able to get an oil tight joint at the head-barrel interface. I tried many times over many years to obtain a good joint with an aluminium gasket. Each time it would hold for a while but eventually would start weeping from the oil drains. Maybe the aluminium head was slightly warped and needed to be skimmed anyway. The ground joint, with o-rings, has eliminated that leak (but there are others!). If I had an engine that held compression and oil with a gasket I would probably carry on using gaskets. Gasket quality is also variable, with some gaskets being too tight around the sleeve nuts and likely to distort unless the holes are opened up a little.

A couple of other thoughts: Would reducing movement of the head/barrel assembly with a head steady make the head gasket less likely to start weeping? Would it be useful to add a second gasket, an aluminium or copper ring on top of the spigot? The thickness of this gasket would have to be carefully chosen so that it would replicate the ground joint ie sealing both on top of the spigot and the wider area around the oil drains. Anyone tried this?

Cheers, Ian McD

Re: Alloy or copper?

Posted by ian_soady at Thursday 11:57

You raise an interesting point about head steadies - as far as I'm aware the OHV singles don't have them whereas the side valves do.

Many OHV singles from other manufacturers do have head steadies fitted and I wonder why Nortons don't.

Re: Alloy or copper?

Posted by John Oldridge at Friday 00:00

Wow gentlemen.........we are in danger of going of topic with this!   As suggested I will go for a lapped joint and 'O' rings.........that seems the way to go.

Ian..........All featherbed framed  engines,  twins and singles  have head steadies, on my M50 (1960 slimline) if it occasionally works loose on the rockerbox bolts, the increase in vibration is very noticeable........It is also an integral part of the frame design to prevent 'flex' on the top frame where the tubes crossover, and if not fitted a facture can occur in this area.

Regards   John O

Re: Alloy or copper?

Posted by ian_soady at Friday 10:34

Thanks John. I wonder why they didn't fit them to the rigids and plunger frames (and non-featherbed S/As?).

Re: Alloy or copper?

Posted by axel_behrend at Friday 17:55

Previously John Oldridge wrote:

I am in the process of re-fitting the cy head on my M50, (a very minor oil leak from the front drain hole ) and wondered if it would be better to fit a copper gasket instead of the alloy one, (for various reasons I don't want to 'lap' the head and barrel).  also someone once posted how to re-torque the head after a small interval to prevent any problems, and I can't find the post, ........any help/advise appreciated.

Regards John O

 

Hallo John!

I'm from Germany,and own an ES 2 with sidecar as well as a Mod 19 - outfit.

As I use both bikes a lot, I was fed up with both types of head-gaskets, alloy as well as copper.

At a classic bike & car show herein Essen last year, I came in contact with a company in Vienna/Austria, which offered to make all kinds of gaskets, even small batches of one or two at very competitive rates. I sent them a used cylinder of an ES2, and they made me 2x head-gaskets, the same composite-material as the modern ones for the Commandos are, with a metal ring around the big opening. Also they made me two gaskets for the bottom of the cylinder, a very special material, that seals best under pressure. I have one set of these gaskets now fitted to my recently rebuilt ES2, and I can say, I'm absolutely happy with that. The whole job cost me around €70,-, a sum in which postage costs of more than € 40,- for sending back the cylinder from Austria to Germany were included!

If there is interest, simply contact me via email: axelbehrend@aol.com, or phone: 00491722476768

Best Regards, Axel

Re: Alloy or copper?

Posted by Albert Sheean at Saturday 08:01

Previously Ian MacDougall wrote:

David,

The decision to go for a ground head joint on my 19S was frustration at not being able to get an oil tight joint at the head-barrel interface. I tried many times over many years to obtain a good joint with an aluminium gasket. Each time it would hold for a while but eventually would start weeping from the oil drains. Maybe the aluminium head was slightly warped and needed to be skimmed anyway. The ground joint, with o-rings, has eliminated that leak (but there are others!). If I had an engine that held compression and oil with a gasket I would probably carry on using gaskets. Gasket quality is also variable, with some gaskets being too tight around the sleeve nuts and likely to distort unless the holes are opened up a little.

A couple of other thoughts: Would reducing movement of the head/barrel assembly with a head steady make the head gasket less likely to start weeping? Would it be useful to add a second gasket, an aluminium or copper ring on top of the spigot? The thickness of this gasket would have to be carefully chosen so that it would replicate the ground joint ie sealing both on top of the spigot and the wider area around the oil drains. Anyone tried this?

Cheers, Ian McD

Hello Everyone,

I fitted a homemade "0.020" copper head gasket to my 1958 model  19s, works nicely. To eliminate the exhaust gasket disappearing act, I made one out of 1/8" soft copper tubing obtained at a plumbing supply shop. Just butt the ends closely together and carbon will fill the minute gap. To reduce top end oil leaks, I made a tappet inspection cover out of sheet alloy then fitted an 1/8' elbow for a breather hose. It's not really noticeable due to the engine's height. I routed my crankcase breather to exit onto the final drive chain as it goes around the gearbox sprocket, the chain is always slightly oily from the vapors discharged. Lastly, I made a cylinder head steady for the engine and noticed an immediate reduction in apparent vibration. A bit off topic I admit but since many of these items were already touched on here, I figured my tuppence couldn't hurt.

Regards,

Albert

Re: Alloy or copper?

Posted by ian_soady at Saturday 10:31

Thanks Albert.

Did you take the head steady to the front downtube or the saddle tube? Any pictures?

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