99 Head Gasket Blowing By

My Dommi 99 which I am slowly building keeps blowing oil and petrol from the rear centre of the cylinder head. I have fitted a new annealed copper head gasket which has been correctly torqued down with all new head bolts, but still the problem persists.Upon fitting the new gasket, I flattened the head on a granite plate, made sure the gasket was soft and didn't use any compound. So, head off again this eve and I can see blow-by between the two cylinders on the gasket. I have re-checked the head and it's flat, so I have then checked the barrels and I can get a 0.0015" feeler under a precision straight edge between the two cylinders.If it was just a matter of flipping the barrels upside down and abrading them on my granite plate, it would be a simple matter, but the tops of the barrels are spigoted so that's not an option.

Do I have to bite the bullet and take the barrels to an engineering shop, or do you think I might stand a chance of getting them correct by using the cylinder head with some marking blue on it and then using a scraper on the cast iron barrels? Or maybe some other method like scraping the alloy head to match the barrels?

Any suggestions very welcome.

Bob

1.5 thou is not a lot, I would have expected the head to pull down and conform to that.

Can you get your depth mic. out and see whether the head is pulling down onto the gasket or onto the spigot? An excessively skimmed/decked head could be held off the gasket by the spigot. Is the spigot developing a crack inline with the gasket surface?

As for gasket goo, if it's good enough for rolls royce....

A light coat of aluminium paint seems to be a little more acceptable to the goo sensitive.

Bob... I'm sure you have checked this..but is the rear centre underside nut holding? I thought mine was but it's not easy to get a 'feel' with a spanner and a torque wrench is more or less impossible. A helicoil solved my similar issue a few years ago.

I always used the composite gasket and never had any problems even when too skint to buy a new one. I think they would be better in your case as they do compress where a copper one will not.

Hi Anna,

As said above, the head was 'torqued down correctly' and following the correct sequences of bolts.

The problem is a one and a half thou discrepancy on the tops of the barrels and there is no way I would like to use any form of gasket goo to 'fill' that gap.

I'm also a little reticent in curving the head with a file to suit the barrel - although that may be an option.

I agree with Robert. It can be difficult to get a seal with solid copper gaskets. Try a composite one before you go down expensive and possibly irreversible machining routes.

The composite gasket does need tightening down a few times and may benefit from a bit of "Wellseal" around the pushrod tunnels and oil drain hole ,best keep Anna happy!. My gasket has lasted for 20 years or more but recently has been blowing oil ,a check with a torque wrench revealed an under-tight couple of nuts ,seems to have stopped leaking now. There are some sub standard gaskets about.

Bearing in mind the Victorian factory these machines were built in I would not have expected a greater degree of accuracy in machining, what you have measured is probably typical. A bit of "blueprinting" would not hurt.

the head is flat but is it square in relation to the heads nuts and bolts surfaces or is it wedge shaped effecting the way it pulls down and seals when torqued up.

Barry

as per diagram exaggerated of course

hello the only way to tell if your cylinderhead is not warped is by removing all studs from barrel and cylinder head and with engineers blue spreadout on a sheet of plate glass put your cylinder head on the glass with the engineers blue on it, and then lift it off and you see the high or low spots in the engineer blue fitting a gasket at this stage is pointless! Has you need to know why the cylinder head is not mating with the barrel in the right way I do know it's more work be Do it right then it will last, yours anna j

The problem is with the barrel .

Previously robert_tuck wrote:

The problem is with the barrel .

If you had the spigot milled off then it would be very easy to fix the barrel. I would grind it on glass rather than ruining my surface plate. A few on this list are running spigot heads with spigotless barrels and seem to be doing fine.

Previously Jonathan Soons wrote:

Previously robert_tuck wrote:

The problem is with the barrel .

If you had the spigot milled off then it would be very easy to fix the barrel. I would grind it on glass rather than ruining my surface plate. A few on this list are running spigot heads with spigotless barrels and seem to be doing fine.

Not ideal Jonathon, and a drastic action for this situation, which could well end up with the head blowing more than before. Bad advice imo. Far better to use a composite gasket and Wellseal. it is only 0.0015".......

I have a vague memory from 50 years ago of blowing between cylinders with solid gaskets, then I switched to the recommended composite ones. No failures in the last 50 years. So far so good, going to uncross fingers now.

As you say Robert, the composite gasket is the recommended one. I think you are making a lot of work for yourself for no good reason Bob. Try using the recommended gasket....

Hello Well I have been telling you this all along, and I just happen to be a Marine engineer since I passedout at 17years of age now 63 years of age Norton motorcycles are just something I owned for the past 46 years some of you just think because I just happen to be female I know nothing about Nortons or engineering But I can firmly say I can throw down the Gauntlet AT any Restorer and do just has good a job

have fun yours anna j

Hello And fitting a composite Gasket may still blow, the first thing you need to know for sure is the Cylinder head true and flat to do this you haveto Remove all Studs for a Start, and Removing Spigot is a very BAD idea Norton had these in place for a reason They only removed them has the Bore got so big they could not be accommodated anymore you find out the hard way there is not many short cuts in engineering

yours anna j

Previously anna jeannette Dixon wrote:

Hello And fitting a composite Gasket may still blow, the first thing you need to know for sure is the Cylinder head true and flat to do this you haveto Remove all Studs for a Start, and Removing Spigot is a very BAD idea Norton had these in place for a reason They only removed them has the Bore got so big they could not be accommodated anymore you find out the hard way there is not many short cuts in engineering

yours anna j

He told us the head is dead flat but the copper gasket still leaks. He may have better luck with a spongier gasket and Wellseal to fill the gap rather than flat surfaces.

Don't argue, Anna knows best!

Previously ian_cordes wrote:

Previously Jonathan Soons wrote:

Previously robert_tuck wrote:

The problem is with the barrel .

If you had the spigot milled off then it would be very easy to fix the barrel. I would grind it on glass rather than ruining my surface plate. A few on this list are running spigot heads with spigotless barrels and seem to be doing fine.

Not ideal Jonathon, and a drastic action for this situation, which could well end up with the head blowing more than before. Bad advice imo. Far better to use a composite gasket and Wellseal. it is only 0.0015".......

Ian, What prompted you to remove the spigots from your 650? Were they breaking up?

Previously anna jeannette Dixon wrote:

Hello Well I have been telling you this all along,

Anna the head is flat, end of. If you had read my post correctly you will have seen that it was the barrels that had the problem, not the head, so please stop going on about it.

I too am an engineer by trade, did a 5 year apprenticeship with British Steel in mechanical and production engineering, so you are not the only one with skills

Bob

Previously anna jeannette Dixon wrote:

Hello And fitting a composite Gasket may still blow, the first thing you need to know for sure is the Cylinder head true and flat to do this you haveto Remove all Studs for a Start, and Removing Spigot is a very BAD idea Norton had these in place for a reason They only removed them has the Bore got so big they could not be accommodated anymore you find out the hard way there is not many short cuts in engineering

yours anna j

He told us the head is dead flat but the copper gasket still leaks. He may have better luck with a spongier gasket and Wellseal to fill the gap rather than flat surfaces.

Anna, you mention 45 years marine engineer.

Can you confirm your education and engineering experience perhaps?

Selby Technical College, City and Guilds Motor Technician.

3rd Engineer ships March 1974 - October 1979.

Security Guard September 1999 to present.

Or is your LINKEDIN profile in error perchance?

Previously anna jeannette Dixon wrote:

Previously Jonathan Soons wrote:

Previously anna jeannette Dixon wrote:

Hello And fitting a composite Gasket may still blow, the first thing you need to know for sure is the Cylinder head true and flat to do this you haveto Remove all Studs for a Start, and Removing Spigot is a very BAD idea Norton had these in place for a reason They only removed them has the Bore got so big they could not be accommodated anymore you find out the hard way there is not many short cuts in engineering

yours anna j

He told us the head is dead flat but the copper gasket still leaks. He may have better luck with a spongier gasket and Wellseal to fill the gap rather than flat surfaces.

Hello Jonathan you alway check things yourself never trust anyone else unless you know them well enough anyone can say the head is true and flat if this was the case then thereshouldbe No gaps anywhere Yours Anna J

You are in danger of becoming a pain in the neck, or some other part of the anatomy, over this. So for some part of the last 45 years you were in marine engineering in some capacity. Many members are highly qualified as professional engineers or as engineering technicians. They seem to have been blessed with a modesty that you lack and a ability to know what it is that they know and what it is that they don't know..

Previously Jonathan Soons wrote:

Ian, What prompted you to remove the spigots from your 650? Were they breaking up?

Correct Jonathan. Mine are + 0.040" and the spigots had cracked. It was a case of a re-sleeve or have the spigots removed. I am not really happy with it, and suspect I will bite the bullet and have it re-sleeved to standard; with spigots! Removing them is the last resort imo, although others have been successful with it. That is why I said it is bad advice to suggest removing perfectly good spigots. With no spigots and a head for a spigotted barrel, I believe it leaves insufficient mating surfaces to guarantee a good seal.

Previously anna jeannette Dixon wrote:

Previously Jonathan Soons wrote:

Previously anna jeannette Dixon wrote:

Hello And fitting a composite Gasket may still blow, the first thing you need to know for sure is the Cylinder head true and flat to do this you haveto Remove all Studs for a Start, and Removing Spigot is a very BAD idea Norton had these in place for a reason They only removed them has the Bore got so big they could not be accommodated anymore you find out the hard way there is not many short cuts in engineering

yours anna j

He told us the head is dead flat but the copper gasket still leaks. He may have better luck with a spongier gasket and Wellseal to fill the gap rather than flat surfaces.

Hello Jonathan you alway check things yourself never trust anyone else unless you know them well enough anyone can say the head is true and flat if this was the case then thereshouldbe No gaps anywhere Yours Anna J

You are in danger of becoming a pain in the neck, or some other part of the anatomy, over this. So for some part of the last 45 years you were in marine engineering in some capacity. Many members are highly qualified as professional engineers or as engineering technicians. They seem to have been blessed with a modesty that you lack and a ability to know what it is that they know and what it is that they don't know..

Previously Jonathan Soons wrote:

Ian, What prompted you to remove the spigots from your 650? Were they breaking up?

Correct Jonathan. Mine are + 0.040" and the spigots had cracked. It was a case of a re-sleeve or have the spigots removed. I am not really happy with it, and suspect I will bite the bullet and have it re-sleeved to standard; with spigots! Removing them is the last resort imo, although others have been successful with it. That is why I said it is bad advice to suggest removing perfectly good spigots. With no spigots and a head for a spigotted barrel, I believe it leaves insufficient mating surfaces to guarantee a good seal.

Unfortunately aftermarket manufacturers are happy to make + 0.040" pistons readily available, and they don't come with a warning on the packet! In fact, Andover Norton, RGM and Norvil all offer +0.060" pistons..... I agree, +0.030" is big enough for the 600/650's, although no-one appears to offer pistons in that size.

Caveat emptor......

Unfortunately aftermarket manufacturers are happy to make + 0.040" pistons readily available, and they don't come with a warning on the packet! In fact, Andover Norton, RGM and Norvil all offer +0.060" pistons..... I agree, +0.030" is big enough for the 600/650's, although no-one appears to offer pistons in that size.

Caveat emptor......

Hello and what their offing are Giardini pistons there must be a mountain of them,And there on the heavy side, JP pistons are the better ones, But All The BHB Original piston went to the USA So there out there hidden someone's ones lock up or garage I found a set of New Old stock Orginal pistons + plus 10 BHB pistons with rings and I have seen too plus 30 oversize to with rings so is a matter of searchingthe internet

yours Anna j

My recent experience has been just the opposite! Having recently had my 650SS re-sleeved back to standard bore my service provider used JP pistons and they were approx 70 grams each heavier than the old, +60 pistons and couldn't be lightened sufficiently. I have now replaced them with Gandini pistons which are lighter than the old ones, so well lighter than the JPs. Additionally I had oil burning problems with the JPs and whilst these were diminishing with mileage the Gandinis have been fine from day one.

Funny you should say that Lance. My + 0.040"'s are BHB, and the borer said they were cr#p, with one slightly larger than the other, which meant he had to bore the cylinders different sizes. As a result the ring gap is really too large, so, despite 2500 miles since, including a change of rings to include the 3-piece oil control rings, it still burns oil.

What with that, the spigots cracking and Norvil having supplied me with a camshaft of I know not what specification, which has proved impossible to accurately time, I am despairing with this engine.

Anna, you mention 45 years marine engineer.

Can you confirm your education and engineering experience perhaps?

Selby Technical College, City and Guilds Motor Technician.

3rd Engineer ships March 1974 - October 1979.

Security Guard September 1999 to present.

Or is your LINKEDIN profile in error perchance?

Funny you should say that Lance. My + 0.040"'s are BHB, and the borer said they were cr#p, with one slightly larger than the other, which meant he had to bore the cylinders different sizes. As a result the ring gap is really too large, so, despite 2500 miles since, including a change of rings to include the 3-piece oil control rings, it still burns oil.

What with that, the spigots cracking and Norvil having supplied me with a camshaft of I know not what specification, which has proved impossible to accurately time, I am despairing with this engine.

Hello And this is All off topic and going no where Yours Anna J

Previously robert_tuck wrote:

Bearing in mind the Victorian factory these machines were built in I would not have expected a greater degree of accuracy in machining, what you have measured is probably typical. A bit of "blueprinting" would not hurt.

I agree entirely, the machine was probably pre war and still machining barrels until the non spigot variety appeared. 0.0015" seems quite accurate for machining around the spigots. Good luck with the scraping, I made my own surface plate as an apprentice in 1960, the hard bit towards the end was trying to remove it from the inspection plate when it would wring itself on, it is still going strong.