bolt
 

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I believe that they are all high tensile. Use once then throw away, replace with new ones.

The head bolts are deffo stretch, not sure on the others, is it worth the risk for a few more pounds?

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They are all re-usable, ive been building scooby engines for over 10 years :)

I'd imagine they can be reused but the likes of the head studs and rod bolts i'd replace personally.

Lol the machines in my work are 110 years old and still have their original bolts and they've been on constantly, the steel used on them is soft. I know they aint an engine though.