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yes the head gasket, thats the done thing with metal gaskets to re-use them

I figured copper spray would be the more appropriate sealer.

i have no experience with copper spray, i've always been told to use hylomar spray on head shims (steel) and when i queried my engine machine shop on re-using MLS gaskets he says he normally washes each layer to remove oil/grit etc and then sprays them with hylomar.

time will tell i guess, but at the moment its working with no leaks!

also googling it seems to bring up aplot of results saying not do much one or the other but saying use copper/hylomar spray or nothing as the two alternatives ?

We always use hylomar on our mls gaskets but on one occasion I had a useless ba falcon 6 that kept leaking no mater what down the side of the block under the extractors something wasn't right and customer didn't want to remove the block to deck it so loaded the head gasket with silver spray paint from a pressure pack and jammed it on didn't leak but buggered if I'd want to remove that head though

but isn't hylomar a thick goopy mess? I have is a tin form and due to its goopyness I only use it for very limited applications as it often does more harm than good.

I find it good around o ring style intake gaskets around only the water ports and some o ring applications. Else where i use the brown aviation sealer ( the tar stuff) that shit is the bomb!

I coat paper gaskets in it and let it soak in an dry to a finger drag tack and it makes the gaskets last much much longer and seals much better. I even used in in a light coat on main seals to aid install and also seals them in really well against possible future weeps as seals shrink a little., just dont use it on tinny shaft seals as the seal may slip out. With hylomar those seals just pop out straight away. So I conclude that although hylomar seals great, but it is and stays as a lubricant making contact surfaces move about easy.

How thick is the spray anyway?

If you get it in the tin yea it's hard to use but it comes in pressure packs which makes it easy to get on in an even coat. Tends to spray on maybe a little thicker than paint 1 coat of hylomar maybe close to two coats of paint from a spray pack and seems to dry out in that state once the air is removed and it tacks off pretty quick used that way

do you have to re-torque it? I imagine you would knowing what hylomar is like. I have used in on thermostat housings and I had to a couple of times until is settled.

Don't really use on anything but head gaskets and most the head gaskets I've done are all TTY so can't really re torque them but it seals pretty good the first time as far as I can tell and were using it on anything from 3l engines to 16l inline 6 with 18-20:1 compression and dirty big turbos pushing 30psi haven't had them blow out or leak after

This is what i use, from what i can tell its good for filling in very small gaps in machining surfaces or gasket imperfections etc. The MLS gaskets are pre-coated with a similar type of surface but after use and washing alot of this can be removed, so its effectively putting it back on.

Top stuff, love cheap horsepower. Even though I have a 265 torqueflite pattern block at home that I will build and run with a mains cap cradle and forged pistons etc I am first going to use the original motor that came with the ute and bolt the turbo to that. It doesn't leak oil and doesn't blow any smoke so I put on a new head with a graphite gasket and will wait to see what happens.