So... what’s your criteria regarding when to use Wellseal and when to use Loctite ?
I'm not sure there is one (a criteria) , being an Antipodean I simply prefer British sealant on a British bike.
Anything troublesome would get ThreeBond mastic, it might even have the edge over Wellseal with high temperature.
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The days of shellac (if that is what they were) type sealers are all but gone that once baked turned into a hard varnish type of thing so no wonder things could leak.
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I have never used any form of 'gasket eliminator ever (iirc) over a intended gasketed joint even if that was what it was for , I think the word used to be gasket dressing and that is what I do, dress the gasket lightly with 515.
The gasket eliminators have merit but not when they are used as a shortcut and used in excess.
So for me it is only used with a gasket sparingly as a back up (Machined surface finish on 50 year old parts can be way different to something contemporary.
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You might even then (in the case of a 850 base gasket) consider this.
Once the cylinder head is in place there is then no access to the four long cap screws, do you torque them (after optional lap checking of the heavy washers) to 30 ft/lbs and be done with it or do you fit the cylinder and retorque it over the following days/week on the bench then fit the cylinder head doing the same cycle.
Not to be confused with over torqueing as another option as there is still the possibility of some settling of the gasket and structure (cylinder / head) . (Its not like it's race day tomorrow)
Everything can be debated(yes I saw the thread)
Do you anneal a copper head gasket ?
On a modern machined surface perhaps not, on a 50 year old machining technology surface perhaps yes so the gasket can conform to the surface at its best with interval retorquing. (Something you would not want on an engine where the through cylinder head fasteners are not accessible after full assembly)
Or you could just slap it all together, it will still run.