Re: Head Bolt Check
The hardened head bolt washers with thread lubricant on both sides helps reduce fricton when torqueing the bolts plus it prevents galling between the bolt head and cylinder head by having a hard smooth surface. If you knew how much torque was required to over come friction from the threads and the bolt head you could add that amount to the spec torque to get the proper clamping force. You don't know what it is so you try to reduce it as much as possible by having clean threads and a friction reducing lubricant.<br />Don likes to follow the book, no problem with that, but the book is not always right ( I have found errors in factory manuals) or the best way and manufactures tend to get by with the lowest cost. Head bolt washers don't cost much but if you add up 100,000 sets the manufacture would use the cost adds up so if they can get by without them they will. Engines that have been assembled and dis-assembled several times tend to have some galling in the threads and under bolt heads which increases friction. This is the reason most race engines use studs rather than bolts for heads and main bearing caps, it saves ware and tear on the threads in the block because they aren't exposed to torque friction.
The hardened head bolt washers with thread lubricant on both sides helps reduce fricton when torqueing the bolts plus it prevents galling between the bolt head and cylinder head by having a hard smooth surface. If you knew how much torque was required to over come friction from the threads and the bolt head you could add that amount to the spec torque to get the proper clamping force. You don't know what it is so you try to reduce it as much as possible by having clean threads and a friction reducing lubricant.<br />Don likes to follow the book, no problem with that, but the book is not always right ( I have found errors in factory manuals) or the best way and manufactures tend to get by with the lowest cost. Head bolt washers don't cost much but if you add up 100,000 sets the manufacture would use the cost adds up so if they can get by without them they will. Engines that have been assembled and dis-assembled several times tend to have some galling in the threads and under bolt heads which increases friction. This is the reason most race engines use studs rather than bolts for heads and main bearing caps, it saves ware and tear on the threads in the block because they aren't exposed to torque friction.
