yes they`re called o-rings, but are not your average rubber/neoprene o-rings

they`re stainless steel/wire rings so they can bite into the head-gasket for sealing a higher pressure

they generally require far more head stud torque to seal properly,,, more like 60lbs , so it`s suggested to obtain some good quality fastemers (head-studs & nuts)

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.