got any head bolts you can part with?

[Ron]

That's interesting... I've seen gaskets made of copper and it didn't matter. Weird!

[David T]

The use of copper was very common on older gaskets usually as rings around the holes that coolant passed through the gasket. Copper is also used as a sealing ring on engines with very high compression around the combustion chamber. The new composite gaskets are part of the system designed to seal the heads to the block. The clamping forces from the head bolts, the compression of the gasket, the pressures inside the combustion chamber, the heating, cooling, expansion and stretch of the bolts is all calculated and tested experimentally till it is all correct. In the PRV the clamping forces must also prevent the liners from moving and maintain a proper seal between the liners, the head and the block. The tensile strength of the bolts, the pull-out forces on the threads in the aluminum, all of this must be just so. That is why it is so important to assemble the engine according to the Workshop Manual using the recommended parts. The W/M does NOT say the head bolts can't be reused. Because it does not say that, one can assume the bolts are not torqued-to-yield. On some motors (not the PRV) the bolts are tightened so much that they stretch and cannot be reused. On some (not the PRV) motors you can actually measure the diameter of the bolts and if they have been used and stretched they are to be thrown away. The procedure for tightening the bolts is also important so that you get and maintain the correct clamping forces which is indirectly measured by the torque of the bolts. On the PRV there really is no good reason to replace the bolts unless they have been damaged or lost. As for the gaskets, asbestos hasn't been used since the 70's in the US. I don't know when it was stopped in Europe but they could have used it till much later. The original heat shields around the exhaust in the Delorean are asbestos! Asbestos is a common mineral and was used for many years in brakes and gaskets and fire-proofing. It was cheap and plentiful and is excellent at absorbing heat. Unfortunately the tiny fibers, once airborne, can cause lung cancer if inhaled. Modern replacements are getting better all the time and are now equivalent to asbestos but are expensive. Asbestos used to be sprayed all over the steel inside buildings to protect it in case of fire. Not anymore! On 9/11, when the towers went down, tons of asbestos went airborne contributing to many of the cancers that later developed. Every time a steampipe in NYC bursts, they have to decontaminate the area because of the asbestos that was wrapped around those old pipes underground in the streets.

[Parzival]

asbestos hasn't been used since the 70's in the US. I don't know when it was stopped in Europe but they could have used it till much later. The original heat shields around the exhaust in the Delorean are asbestos! Asbestos is a common mineral and was used for many years in brakes and gaskets and fire-proofing. It was cheap and plentiful and is excellent at absorbing heat. Unfortunately the tiny fibers, once airborne, can cause lung cancer if inhaled. Modern replacements are getting better all the time and are now equivalent to asbestos but are expensive. Asbestos used to be sprayed all over the steel inside buildings to protect it in case of fire. Not anymore! On 9/11, when the towers went down, tons of asbestos went airborne contributing to many of the cancers that later developed. Every time a steampipe in NYC bursts, they have to decontaminate the area because of the asbestos that was wrapped around those old pipes underground in the streets.

Thermal systems insulation or (TSI) is the most dangerous asbestos containing materials. That's what is on those steam pipes (its class 1) it has high concentrations of asbestos, and its easily crushed or pulverized (the term used is "Friable") Asbestos used in vinyl floor tiles for instance is far less dangerous as there is basically no way for the asbestos fibers to be freed (short of grinding it up with an angle grinder or something)

I lived asbestos everyday, and held every certification the EPA ever dreamed up as far as asbestos goes. Largely I worked as an analytical microscopist, I actually had to look at asbestos everyday, and even count fibers per square micron. Its an amazing material for everything but breathing.