I am bolting homemade parts to my block and wanted to know any rule of thumb for how deep a bolt has to be.  does an 8mm bolt need 8mm of thread depth?   a certain number of threads?  are socket head bolts as strong as hex, at least for the intake/exhaust manifolds?   when do I use lock washers?   I always wondered why Lycoming engine case halves never had lockwashers and used std (not fine)threads.(at least mine came that way)    kevin   n3773@comcast.net <mailto:n3773@comcast.net>