Thread: Vin # and plastic head dowels

Originally Posted by Ean Austral

Am sure I read somewhere that the head bolts cannot be re used or re tightened...This always never made sense to me, but just assumed they were some type of bolt that may have been heat affected by the different metals they went thru/into..

Surely even if you replaced them 1 by 1 then its got to be a better option than the head gasket failing..

Something for someone who is not far from changing a head gasket to try..Makes sense to my small brain..

Cheers Ean

Thats correct, the reason being is because they are know as "stretch" bolts, as they actually stretch in length when torqued down, my post was a bit way off tbh as its not the done thing, but "if" you was to replace one at a time, who knows how effective it would / could be.

Torque to yield is just that, the bolts are of a specific material, length and diameter etc to be in the yield range of their tensile strength. This range is followed by the plastic deformation range, which is permanent failure, with a change in relaxed length, a removal of tensile strength for the unit itself.

This is why they cannot be re used or retensioned.

Basically, they are designed to act as a 'spring' to continue clamping force at a steady state.

High thermal or tensile loads outside the materials design strangth will render them useless.

JC