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99 Head Gasket Blowing By

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99 Head Gasket Blowing By

Posted by Bob Matthews at March 07. 2017
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

Re: 99 Head Gasket Blowing By

Posted by anna jeannette Dixon at March 08. 2017
Previously Bob Matthews wrote:
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

 Hello Well a do have a cylinder head alloy file  it was made for Lycoming  flat four engines  cylinder head    but did you do up you cylinder head from the centre outward   starting with centre stud that the front three studs and then the back stud under the back of the barrel  and then the four side bolts do these up in stages  then the two under the barrel front then the two front in between the rocker boxes  and have all four rocker adjusters fully slackened off you can play with the pushrods after you have the head fastened down and torqued up right     and do  try using  Stag Wellseal  put it no with a small paint brush artist size  brush  brush on both size of gasket stag wellseal does not dry out     have fun  yours anna j  

Re: 99 Head Gasket Blowing By

Posted by Bob Matthews at March 08. 2017

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.

Re: 99 Head Gasket Blowing By

Posted by Martyn Watson at March 08. 2017

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....

Re: 99 Head Gasket Blowing By

Posted by Martyn Watson at March 08. 2017

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

Re: 99 Head Gasket Blowing By

Posted by David Cooper at March 08. 2017

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.

Re: 99 Head Gasket Blowing By

Posted by robert_tuck at March 08. 2017

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.

Re: 99 Head Gasket Blowing By

Posted by anna jeannette Dixon at March 08. 2017
Previously Bob Matthews wrote:

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.

Hello Stag Wellseal is no ordinary gasket Goo  Has you call it!!   I have used this stuff for years  on 6-inch diameter  flanges  for high-pressure steam  up to 800 PSI  with no problems, It sounds to me to be a problem with the head not fitting over the spigot   now try this out for size   have you any engineers  blue  if not I could send you a small pot full  I have tons of the stuff    now with your engineers blue  put on the cylinder head recess  by a small paint brush   with all  studs removed and no push rods in the way  fit the over the barrel spigots  and then you see where it's not seating down fully   the other way of flatting off a cylinder head, Is by using a nice size Glass  8mm thick and valve paste  course to start with  and rub the cylinder on the glass with valve paste on the side you need to flat off  in a crucial motion  and you can file the  recess that fit to the spigot  with a small needle file   i have sets of these to  all sizes  and some gasket do not fit right has well these need a file around them  has well   have fun   you know where to find me if you get  stuck with it      yours anna j

Re: 99 Head Gasket Blowing By

Posted by Gordon Johnston at March 08. 2017

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.

Re: 99 Head Gasket Blowing By

Posted by robert_tuck at March 09. 2017

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.

Re: 99 Head Gasket Blowing By

Posted by Bob Matthews at March 09. 2017

Thank you all for your suggestions.

Indeed 1.5 thou is not that big a gap and I too would have expected either the head to 'pull' down or the gasket to compress by that amount, the Norton head must be very rigid indeed.

I have checked the spigot height by fitting the head sans gasket and checking the gap between head and barrel (there is none) and by measuring the spigot height (0.130") and head recess (0.139"), the gasket is from RGM and is 40 thou.

I have also checked that every single head bolt is not 'bottoming' out on the threads and does indeed clamp the head.

I am sure that the use of a composite gasket and some 'goo' would probably solve my problem, but I feel it's not really the proper solution as I would like both surfaces to be as flat as possible.  I can just imagine being 100 miles away from home going flat out uphill and blowing out the gasket then having to limp home on a sick engine.

I did some scraping and filing of the barrel tops last night and have improved the situation a little - it's a slow process - so I will continue for a few more hours and if I can't achieve what I'm after, then it will be off to the engineering shop.

 

Strange that the barrels have this concave surface to their tops and I can only assume that they came from the factory like this 57 years ago - maybe a 'Friday afternoon job'.

 

Bob

Re: 99 Head Gasket Blowing By

Posted by robert_tuck at March 09. 2017

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.

Re: 99 Head Gasket Blowing By

Posted by Barry Carson at March 09. 2017

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

 

 

 

Attachments

Re: 99 Head Gasket Blowing By

Posted by Bob Matthews at March 09. 2017

Previously Barry Carson. wrote:

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

 

Hi Barry

I can only assume that it is perpendicular as there seems to have been very little removal of material from the head mating surface - I almost expected to see the head face flush with the cooling fin on such an old engine - but this is not the case.  I will put an engineer's square on the bolts when I get home this eve, but I am expecting it to be square.

 

 

Re: 99 Head Gasket Blowing By

Posted by anna jeannette Dixon at March 09. 2017

hello the only way to tell if your cylinder head is not warped  is by removing all studs from barrel and cylinder head  and with engineers blue spread out 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  

Re: 99 Head Gasket Blowing By

Posted by robert_tuck at March 09. 2017

The problem is with the barrel .

Re: 99 Head Gasket Blowing By

Posted by Jonathan Soons at March 10. 2017

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.

Re: 99 Head Gasket Blowing By

Posted by ian_cordes at March 10. 2017

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".......

Re: 99 Head Gasket Blowing By

Posted by robert_tuck at March 11. 2017

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.

Re: 99 Head Gasket Blowing By

Posted by ian_cordes at March 11. 2017

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....

Re: 99 Head Gasket Blowing By

Posted by Bob Matthews at March 11. 2017

Update:

I went to see the 'main man' in my area last night, he's a highly respected mechanic who has worked on British motorcycles for more than 60 years and still produces some stunning restorations at an alarming rate.  He has confirmed what some of you are saying about the solid gasket.  Apparently all modern copper head gaskets are too thin to give good compression and compliance (the RGM one I used is only 1mm thick) and to use solid copper it would have to be 2mm thick or use 2 gaskets.  Better still is to use a composite gasket which I now have on order.  The 'original' gaskets were apparently a very tight fit over the spigots and the spigot to barrel top surface had a small radius which causes the gasket to curl up very slightly at this joint upon tightening the head down to create a gas tight seal.

He also gave this advice - when tightening down the head, tighten the centre bolts 1, & 2 and leave the head for 10 minutes or so before tightening the other bolts, then torque the centre bolts and again leave for about 10 minutes before torquing the others, this allows to head to 'relax' into its final position.  He also said not to use any compound.

By scraping and filing I have now reduced the scalloping of the barrels to less than half a thou.  (I discovered during my work that someone in the past had aggressively cleaned the tops of the barrels with either a flap disc or an extremely coarse wire brush in a drill to cause the dishing).

Hopefully by early next week I should have my final fitment of the head :)


Re: 99 Head Gasket Blowing By

Posted by anna jeannette Dixon at March 13. 2017

Hello  Well I have been telling you this all along,  and I just happen to be a Marine engineer since I passed out 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   

Re: 99 Head Gasket Blowing By

Posted by anna jeannette Dixon at March 13. 2017

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 have to 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

Re: 99 Head Gasket Blowing By

Posted by Jonathan Soons at March 13. 2017

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 have to 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.

Re: 99 Head Gasket Blowing By

Posted by Bob Matthews at March 13. 2017

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 :P

 

Bob

Re: 99 Head Gasket Blowing By

Posted by John Shorter at March 13. 2017

Don't argue, Anna knows best!

Re: 99 Head Gasket Blowing By

Posted by Jonathan Soons at March 13. 2017

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?

Re: 99 Head Gasket Blowing By

Posted by anna jeannette Dixon at March 14. 2017
Previously Bob Matthews wrote:

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 :P

 

Bob

     Hello try 45years  marine engineer    
 
anna j

Re: 99 Head Gasket Blowing By

Posted by anna jeannette Dixon at March 14. 2017
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 have to 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 there should be No gaps anywhere     Yours   Anna J 

Re: 99 Head Gasket Blowing By

Posted by Gordon Johnston at March 14. 2017

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?

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