I'm not trying to turn this thread into a black/vs copper headgasket slugfest, nor am I saying the BK450 is now better or worse than`twas before, but-

We just put a new BK450 head gasket on a member's 1360S.
Then started the motor, ran until hot, retightened it again.
Noted the nuts had all loosened from 42 to 30-35ft/lb.
They all took near 1/2 a turn.
Please retighten these gaskets (and readjust rockers) when first hot, don't just assume she'll be right for 1000 miles or so and go for a drive....
And I'd check again at 500-1000 miles too.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Sound advice. Applies to all gaskets. Including S/S gaskets. I had an RB25 in my workshop the otherday, guy didn't re-tighten... it started at 80ft/Ibs and ended up at a low 70 something.

Who doesnt retighten head gaskets? Geez I even retighten monotorque head gaskets. I guess the people that dont retorque are the ones on the side of the road.

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Have a Nice Day.
If already having a nice day please disregard.

I've always retightened them twice but many don't.
However I've not seen them go down this much when redone hot.

I was going to add, tetightening applies to Monotorque ones too. They are good gaskets, just don't believe the monotorque blurb.

In the old days, I was taught to always retighten iron heads (particularly grey Holdens) hot, but alloy heads or complete motors cold.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

My dad always taught me to re-tension head bolts. I still do as I'm told.

I just fitted another gasket to a Cooper S (different car), used a BK450 NOS `Made in UK' one this time.
Retorqued it when hot, and it hardly went down at all. Rocker clearance was still correct.

Make of this what you will... but to me, there seems to be a difference in construction between the UK made BK450 and the current Belgian made one (Both in Payen packaging).

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.