Joined: Thu Oct 5th, 2017
Interests: Science, technology, horses
Reputation Points: 1923
Is it standard procedure to replace head bolts nowadays? Back in the 1970’s when I twisted wrenches for a living, we never replaced the head bolts. I guess things change without me noticing. Of course, I haven’t changed a head gasket since the mid nineties.
Many modern engines have single use bolts now - they are torqued up to the yield point so reusing isn't a good idea!
The K series Austin Rover engine has bolts that run right through the head & block and screw into a frame that carries the crank bearing caps in the sump! This amazingly light and strong engine has fully floating cylinder liners and basically falls apart once the bolts are removed!
Instead of using a series of bolts to close the cam carriers-to-head and head-to-block and block-to-ladder, the K does this by using one long bolt which goes right the way through the engine. The metallurgy of this bolt has been very carefully designed and the torquing at 64Nm brings the bolt to its yield point. Effectively the point at which the bolt will stretch with the block under its cyclic loading, to distribute these loads very evenly throughout the block.