I recently discovered that the bolts which fasten the cast iron cylinder front cover (215 six) to the front engine support had been held in place pretty much by rust. Three of the four bolt holes in the cast iron cover were shot. I have successfully drilled and retapped so I can bolt these pieces back together. When I bought the bolts this morning, all the store had were 6-point hardened. Now, I'm pretty sure that when I torque these guys down, I won't risk stressing the bolts. But what about the cast iron? My question is : 1/2 inch diameter coarse thread into 11/16 inch thickness of cast iron...where would I find torque values for this? Note: I don't plan to crank on this thing to a point where I'll mess anything up. I'm just curious if the metal that the bolt is threading into is as much a determinant as the bolt itself when specifying torque. Thanks

 

"I'm just curious if the metal that the bolt is threading into is as much a determinant as the bolt itself when specifying torque."

Generally speaking, no. A torque spec is designed to stretch the bolt by a determined amount. A quality bolt will keep pressure applied consistently. This wouldn't apply in all cases. For example, a valve cover gasket will be destroyed long before you ever stretch a hardened bolt.

You obviously have to use some common sense if you have a bolt that isn't stock, and threads of questionable condition. When talking about an engine cover or anything of similar importance. I would go a little light on the torque, and add some insurance like a lock washer and/or a liquid thread locker.

 

I have to second the thread locker. Get a good Locker from Loctite and let it do the work of holding the bolt in not torque. Especially since you question the reliability of the threads. Then all you have to do is snug the bolt down very little so you don't strip the threads and the Loctite will hold it in.