Head bolt leak.

[Ian Williams]

This is an interesting thread, like Jim I have in the past lapped heads and blocks, fitted gaskets with a smear of grease and not had issues. More recently I have been having the top of the blocks and heads very lightly skimmed by the machine shop who do my reboring, they obtain a nice fine finish and only remove the barest minimum of metal. However I have recently started to discover issues both on engines I have built and on engines where head gaskets were fitted by others. There is evidence of water seeping across the gasket into the bores, this leaves rings of pitting around the bore at whatever height the piston was sitting and also sometime damage to valve seats. Occasionally there is evidence of water bubbling up the central stud where the gaskets get hottest and are under most stress, other times nothing until the engine is stripped for a valve grind or other work. This is a new one for me, I have still to come up with a conclusive answer, gaskets have changed we no longer get Payen, and I am not lapping heads but having them ground. I would immediately suspect the latter if it were not for the fact that other engines have exhibited the same issues where they have not been through my hands.

[Hedd_Jones]

If the cars were being run on plain water as they would have done when designed and built in the early 1920's any leaky studs in the lock would soon seal of their own accord as they rusted up. Of course the threads when new would have been nice and accurate and easy to seal. This is how we seal rivetted pressure vessells on our steam engines. We accellerate the sealing by urinating in the water

Nowadays most blocks are cracked between 2 & 3. The threads are either original and worn or stretched or new and bigger or helicolied. Theres no wonder they leak, particularly given the use of antifreeze.

I put a mixture if steam oil (1000 grade) and graphite flake made into a thick paste on the studs for the head and manifold and this seems to work well when it come to take the offending article off. Even on studs sealed only at the nut end.

The RP will have had a new gasket on it, but father only ever used grease. There is a block ready to go on the bench should the addition of goo not be successfull. The head gasket (and new water manifold) is on order.

[Colin Reed]

HI Ian,
When the head & block are either skimmed on a grinder or hand done.are all the water corrosion marks removed.
because if any black marks remain they are porous.    one solution is to bore out and weld in plugs which are then redrilled.
 just a thought

Colin NZ

[Ian Williams]

Head it is not water coming up stud threads but seepage across gaskets, I always seal all studs, and the seepage is obvious when reading the gasket.
Colin yes good thought, the waterways are often corroded so plugging and re drilling them may help. What I can not get my head around is why the change, for me this is a new issue that has manifested in the last 10 years, and why do some people report having no problems whatsoever. Perhaps there are a lot of gaskets currently seeping and going unnoticed because the cars do comparatively low mileage, perhaps when a few more engines have the heads removed for valve grinds we will start seeing more issues. But the question remains as to why it happens on sound flat blocks, and if there is an issue how we fix it. My feeling is there must have been a change in the composition of the gaskets which prevents them compressing evenly under our modest stud tensions. Currently I am having reasonable success with a light coating of Hylomar spray, but I know some old hands who swear by aluminium paint.

[JonE]

Ian - I presume Hylomar spray has less mass in it than the Loctite product? Is that something you would advocate only if the surfaces have been meticulously prepared?

[Bob Culver]

I suspect whatever modern substitute gaskets are made of, it is inferior to the old. I ran my Seven then a Javelin for decades with heads very frequently off both, and reused gaskets. The wet liner Jowett cars with different expansion rates are somewhat more prone to gasket trouble than other makes. But present owners seem to experience a lot of random head gasket failures at low mileage and this despite improved and standardised fitting procedures.

[Ian Williams]

I am not advocating for or against either product particularly Jon, I am simply saying that I am still experimenting but have had reasonable success with the Hylomar, however there may other products equal of better. I think any installation will benefit from meticulous preparation and I am very interested in hearing others experiences in order to learn.

[Chris KC]

HI Ian,
When the head & block are either skimmed on a grinder or hand done.are all the water corrosion marks removed.
because if any black marks remain they are porous.    one solution is to bore out and weld in plugs which are then redrilled.
 just a thought

Colin NZ

I've used a similar approach on a head without catastrophe so far. The water passages were slowly 'growing' at the gasket face so they were over-bored, threaded, plugs screwed in (with Loctite) then re drilled. The whole thing given a light skim after to ensure flatness.

[Hedd_Jones]

Ian. I would suggest that leakage up stud threads is far more common than you think it is. As for gasket leakage It is without doubt the composition of the gaskets. On my steamer I try to use only asbestos jointing, and have a good stock of it. But occasionally have to use modern equivalent in the larger sizes. With a smear of the graphite flake/oil paste I mentioned earlier tje asbestos can be re used time after time. The modern stuff gernerally fails at the first part. And is far less tolerant of marked lands. Its not unusual for a joint made with modern gasket to have to be remade due to leakage. Its unusual that an asbestos joint has to be remade.

[carfan]

Informative thread , very interested to see recommendations for high temp copper silicone Loctite 5990 for head gasket installation. ( Am at a copper composite head gasket on a side valve engine , bigger than a seven  )

I note to apply thinly , presumably one still needs a complete coat ,what does anyone use to apply it / spread it ?

I would be afraid of excess 5990 squeezing somewhere it shouldn't ,when torqueing down !

I'm guessing best approach is  to lay the gasket down & apply the 5990 to the block side of the gasket & also to the head ?

Presumably one needs to be reasonably quick doing applying the 5990 & torqueing down , as you don't want the silicone starting to set up ?

Interested to get any tips .