Just was putting the head on and one of the bolts 'felt funny' when I was going from 20 to 25 ft/pounds. I took it out and it looked like this.
That is typical of chinese made hardware, on any job that is important, it is important to be sure of the quality of the parts, and there is no way you can be sure of any bolt or nut made in china. US or European mad bolts are more expensive, but worth the money. I would remove all the head bolts and get quality ones, or you will pay more in the future.
Best
Gus
Here's a little OT: If the head torque is 55 lb, a grade 5 bolt will stretch a little in its elastic range to grip. Will a grade 8 bolt not be in its elastic zone at that same torque, causing it to come loose easier?
Same factory?
Ralph, I think the elasticity is the same on all steel bolts, but the grade 8 bolt has a longer range of elasticity before plasticity begins and the bolt gets permanent deformation (and soon breaks if more torque is applied).
Many modern engines are designed so the head bolts gets some plastic deformation when correctly mounted, so you have to get new bolts every time the head is taken off. Not so with the T if quality bolts (or studs) are used.
Thanks, Roger; you are a fantastic resource of knowledge.
I guess that's why I never heard not to use a grade 8 in place of a grade 5...
rdr
Roger, is something gained with the modern engines having plasticity at correct torque? Just curious if it is price of hardware or something else?
I'm not sure here, not designing engines - I'm at the exterior/sheet metal department - but I think it has to do with designing the head fastening so you won't need to retorque after the engine gets hot the first time. Much less problems with rational production flow if one torque (plus a certain angle) is enough. Many (most) engines will run their whole life like 300,000 miles without the head off ever - amazing when you think about the working conditions for an exhaust valve..