Originally Posted by bygddy
Honestly? No idea.....just what I have always been told to use for ultimate strength....
The only time you need "ultimate strength" is when under ultimate stress.
This is all about keeping well away from ultimate stress.
You cannot tighten the head bolts any tighter and it won;t help
anyway if you did. All you will do is crack the head or strip the threads out of the block.
Won't keep the head gasket in any better.
When you keep combustion normal , without detonation, there is no excessive stress.