This is a general small engine question.
When installing OHV head bolts I am sure they should be clean but should they be lubricated prior to torquing? If so should just the threads be lubed or should the underside of the bolt heads get some too?
Thanks to all who responded to my 12.5 hp
Vertical questions a few days ago.
Knots
#2
Scrubcadet10
I've never lubed head bolts (unless stated by the manufacturer, which is rare for small engines). i just make sure they're clean and torque them... i usually run the engine to operating temp for a while, let it cool down, and recheck... occasionally 1 or 2 may need a 1/4 turn or so.
No .
Unless otherwise stated all torques are for a clean dry new bolt in a clean dry hole .
Any lubrication will reduce the friction thus lower the torque readings on your tension wrench.
Tension wrenches do not measure tension, they measure the resistance of the thread to the rotation of the wrench which the engineers convert to clamping tension via the type & pitch of the threads.
The long & short of it is lubricated threads are torqued to a much lower reading ( up to 40% ) to achieve the same clamping force .
The other problem is excessvie oiling can fill a blind bolt hole and split the castings .
