Silicone gasket choice

You can talk about almost anything here

Moderators: John@sos, charlesp, Charles uk, RickUK, Petergalileo

User avatar
40TPI
Posts: 451
Joined: Fri Jan 26, 2007 7:08 pm
Location: North Buckinghamshire, 110 miles south of Yorkshire, England.

Silicone gasket choice

Post by 40TPI » Wed Mar 12, 2008 2:55 pm

There is a very large number of silicone "instant" gasket products available. Anybody in the UK care to share their preferred choice for use with our copper head gaskets on Seagulls? And probably most importantly why the nominated product is their preferred choice?

Peter

Vic
Posts: 629
Joined: Fri Nov 03, 2006 4:26 pm
Location: UK

Post by Vic » Wed Mar 12, 2008 8:04 pm

I would have thought that a silicone instant gasket product was quite inappropriate for this use.

They are intended aren't they to be used in place of a gasket not as a gasket cement.

I thought the copper gasket on a Seagull should be annealed and used on its own.

Ian Malcolm
Posts: 108
Joined: Thu Mar 30, 2006 11:42 am
Location: London, ENGLAND

Post by Ian Malcolm » Wed Mar 12, 2008 10:27 pm

Silicone Gasket compound is *rarely* the right stuff for *any* engine. (except where specified by the OEM)
and is *NOT* a gasket dressing

If reusing a head gasket, thin down some Hermetite red (non-hardening, high temperature tolerant) with a little thinners and brush evenly on both sides of the annealed gasket, and the joint faces or spread the thinnest of smears with an old credit card . If the sheets of copper the gasket is made of are seperating a bit, take a sheet of stiff paper and work some of tye thinned compond down between the sheets. Allow to dry till barely tacky before assembly.


Hermetite Red and Hylomar Blue should find a place in everybody's toolbox.

User avatar
John@sos
Posts: 614
Joined: Fri Mar 03, 2006 8:16 pm
Location: Essex, UK
Contact:

Silicone gasket sealant

Post by John@sos » Thu Mar 13, 2008 12:22 am

Contrary to the excellent advice already given on this subject, I have to add that in the latter days of British Seagull ALL the motors were sealed with orange heat proof silicone sealant!


Years ago Seagull issued a memo recommending the stuff for head gaskets (they even placed rubber tube of it in gasket sets for a while, till they realised it would have gone off by the time the dealer sold the set!)

All crank halves were sealed with it as well as cylinder bases and gearboxes.

The thinking was that it would take up any slight discrepancies, especially on used motors with slightly corroded heads etc.

I have used it extensively for 15 or more years and though it can look untidy if not cleaned off, it does do what it claims to do, 'seal'

This is not to say you cannot use other sealants, it is just what Seagull, and I have found to work.!

I also use the black heat proof silicone to seal round the top of exhausts, and for sealing ht leads into the rubber caps, it is the right colour not to be seen! and it works again!

Hope this helps,
John
SOS

Ian Malcolm
Posts: 108
Joined: Thu Mar 30, 2006 11:42 am
Location: London, ENGLAND

Post by Ian Malcolm » Thu Mar 13, 2008 11:50 am

Interesting information John!

As I said,"except where specified by the OEM!"

It seems that Silicone sealent is fully approved by Seagull for just about all the joints in a Seagull.

Using it as a gasket dressing *IN* *ORIGINAL* *PRODUCTION* still smells of bodgery though. I wonder if they were having quality problems with their castings in later production or if they just couldn't be @rsed to keep more than one type of gasket compound on the production line.

I personally dont like Silicone sealent because its *so* fussy about surface cleanliness and I've seen a *LOT* of water penetration past joint surfaces and gaskets dressed with silicone over the years due to it failing to bond totally to the joint or gasket face and capillary wicking happening through the hairline gap (outdoor electrical equipment housings, not even immersed). Invariably, if the housing was undamaged, a good solvent clean of the joint faces, a new lightly greased gasket and evenly tightening (but not overtightening) the fastenings provided a total cure.

However as Silicone is sanctioned by the OEM, + John's years of experiance that it *actually* *works*, one would be a fool *not* to use it where appropriate. If one has *got* to use the stuff, I've had better resuts with the orange goop than any of the others It *still* sets in the tube before you next use it though - another reason to dislike the stuff.

If using Silicone for electrical purposes (HT lead!), It is *ESSENTIAL* to use a grade that does NOT liberate acetic acid while curing. This may be labelled as 'electrical grade' 'acid free cure' or 'oxygen sensor safe' The ordinary stuff *will* corrode right through a copper wire or contact in time. The thinner the wire the sooner the trouble.
The fumes can also do damage although not as quickly as direct contact.

As the commonest black pigment is carbon black and high temperature Silicone is not likely to be specced for electrical applications, I'd personally choose to use CLEAR silicone on HT leads.

If you want a gasket dressing for all except top end and fuel system applications, I strongly reccomend Hylomar Blue - originally developed by Rolls-Royce to keep the oil in :-)

http://www.hylomar-usa.com/_resources/_ ... ducts.html

I would still stand by Hermetite Red for top end applications, I have just put a year's running on a Yanmar 1GM10 single cylinder diesel with no trouble that I had the head off to regrind the valves after it let me down on passage. I had no choice but to reuse the original gasket, many years old, with *carefull* application of Hermetite. No water in the oil or cylinder, No loss of compression
and thats with minimal onbord tools, torquing the head nuts by educated feel.

User avatar
John@sos
Posts: 614
Joined: Fri Mar 03, 2006 8:16 pm
Location: Essex, UK
Contact:

Silicone

Post by John@sos » Thu Mar 13, 2008 12:47 pm

Hello Ian,
You are dead right about the Silicone needing to be on clean surfaces, and it can leave an aweful mess if not cleaned up. Does not look 'proffessional' sometimes.

Prior to the recommending of silicone Seagull did not recommend ANY sealant on their gaskets...

Re the HT lead application. I recommend replacing leads at least every 5 years, (Not the 1 year Seagull recommended) Asthe rubber caps tend to crack in 3 the silicone does not have time to damage the sopper,if indeed it gets into contact with it.

If you can get hold of electrical grade fine, but as you say, they stuff goes off in the tube so the next time you reach for it, it is solid!

Sadly old Seagulls do need a bit of extra help sealing heads especially, and that orange stuff seems to work for me...

The Blue Hylomar keeps longer and yes Ihave it in my tool kit!

The Orange I use is 'Comma' brand.

Regards,
John
SOS

User avatar
charlesp
Posts: 2564
Joined: Mon Mar 06, 2006 1:37 pm
Location: Poole, Dorset, England

Post by charlesp » Thu Mar 13, 2008 1:14 pm

There was in fact one short period when British Seagull used sealant - they actually specified a Bostik compound whose number I have somewhere.

This was in the days of the FV, FVP, and LS. The 'Little Model Forty and its brethren had that strange aluminium-steel-iron-aluminium construction which made the power head extremely susceptible to corrosion.

Reassembly was recommended with 'liberal' amounts of the stuff smeared over the jointing faces of the gaskets and around the roots of the studs.

If you get one where this has been done it's challenging to prise apart, the stuff hardens over time into something more akin to Araldite.

User avatar
40TPI
Posts: 451
Joined: Fri Jan 26, 2007 7:08 pm
Location: North Buckinghamshire, 110 miles south of Yorkshire, England.

Post by 40TPI » Thu Mar 13, 2008 1:31 pm

OK I‘ll come clean on why I posed the question. Having had more tubes of Hermetite ooze across my toolbox trays over the years than I care to remember my unthinking action as an older biker would be to simply anneal and re-use without any gasket dressing. To date the block surfaces I’ve seen on rebuilds have not been that bad and I have simply annealed and refitted without trouble. The head surface of the 1980 model 90 block in front of me looks terrible and brought to mind CharlesP's assertion that foundry and machining quality suffered badly in later years. I have a good example here!

Now I’m also aware that modern high performance engine joint sealing and gasketting is an integral part of the overall engine design concept and has required the development of new materials to solve new problems. The resulting new gasket dressing and gasketless sealing products just might bring benefit in our old tech engines.

Having read British Seagull’s recommendation in the service manual to use (now) old fashioned Wellseal as a dressing at Service Sheet No. 4 and then seen John at SOS prescribe high temp silicone RTV I decided to find out who had started to experiment with what and why. So please, John and anybody else, which brands have you used ?

Peter

ps I'm really going to learn to key faster when I start a reply. I see John has answered the question before I got the above posted up !!

bruce nickerson
Posts: 106
Joined: Mon Feb 04, 2008 9:06 pm
Location: USA- Boston area

annealing head gasket

Post by bruce nickerson » Fri Mar 14, 2008 9:44 am

A few mentions of annealing head gaskets in this thread. How do you do this?

User avatar
40TPI
Posts: 451
Joined: Fri Jan 26, 2007 7:08 pm
Location: North Buckinghamshire, 110 miles south of Yorkshire, England.

Post by 40TPI » Fri Mar 14, 2008 1:26 pm

Depends on who you have to answer to. Either the gas ring on kitchen cooker or the propane torch in the workshop is good. Pliers/grips are mandatory.

Peter

bruce nickerson
Posts: 106
Joined: Mon Feb 04, 2008 9:06 pm
Location: USA- Boston area

annealing

Post by bruce nickerson » Fri Mar 14, 2008 2:23 pm

40TPI:

TYVM I am master in my household, at least while my wife is at work. I am now fully retarded and am no longer employed.

Since I am old enough to have gone through my undergaduate engineering training using a slide rule and am now suffering from CRS (Can't Remember S--t) I have forgotten most of my metallrugy.

You have listed the tools, but how much to heat the gasket?

Vic
Posts: 629
Joined: Fri Nov 03, 2006 4:26 pm
Location: UK

Post by Vic » Fri Mar 14, 2008 3:46 pm

how much to heat the gasket
heat until a dull red
..............................but see
http://www.motorcycle.co.uk/reference_a ... inium.html

bruce nickerson
Posts: 106
Joined: Mon Feb 04, 2008 9:06 pm
Location: USA- Boston area

gasket

Post by bruce nickerson » Fri Mar 14, 2008 4:06 pm

Vic:

TYVM. Good site!

User avatar
Charles uk
Posts: 4772
Joined: Wed Feb 27, 2008 4:38 pm
Location: Maidenhead Berks UK

Post by Charles uk » Fri Mar 14, 2008 8:32 pm

I heat mine with a gas torch gently all over, on a block of wood until I see the first few green flickers appear in the gas flame,

That's it, remove heat & let it cool.

This is what I do every time I remove a head, then I coat with a very thin coat of any high temp RTV.

I must have used every colour, the only problems I've found are that the excess that squeezes from the joint forms rubbery spaggetti that could block water ways, & the ones that have better adhesive properties stick the head on so well that a knife is needed to remove it causing some damage to the gasket, this being the only reason I've found to fit a new gasket.

Charles in NZ

RickUK
Posts: 483
Joined: Wed Mar 08, 2006 12:58 pm
Location: Huntingdon

Post by RickUK » Fri Mar 14, 2008 10:30 pm

Call me old-fashioned- copper is annealed by heating to a dark brick-red colour with flashes of green in the flame (the copper oxide burning off) - and then chilling in cold water - maybe air cooling is OK. This is opposite to steel which is hardened by heating and quenching.
If making copper cooling pipes from a new copper coil, do as much as possible by hand and use benders where necessary, but after manipulating the pipe, it will then be work hardened and need annealing for further major bending later.
Any gasket faces need to be immaculate before making a joint, and assuming a copper gasket is in good condition, only a smear of lubrication is necessary, but sealants are invaluable in the right situation - eg erroded faces etc blah blah! Rick.

Post Reply