Join Date: Mar 2002
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Re: Intake Manifold leak, how hard to do myself?
When wrenching, always do your best to apply counter torque to the head of the wrench... in other words, if at all possible, put one hand on the wrench handle and another on the socket wrench head or wrench head. Push and pull with both hands at the same time.
The idea here is that you want to do as much as you can to eliminate any force on the bolt that is not a twisting force (torque) centered on the axis of the bolt. When you pull with just one hand at the handle on the wrench, you are applying a tremendous amount of shearing force to the bolt as well as twisting force (torque - what you want).
Some bolts are all but impossible to do this with due to their location and others will shear even with proper counter torque applied due to them being brittle from heat cycling. Header bolts are some of the worst for this. Keep in mind that any time you use a universal joint or swivel to get a socket on the bolt head, you are complicating the torque path, reducing the effective torque you are applying to the bolt, and probably not going to be able to avoid applying some shear force in the process. Don't try to overcompensate for the complicated angle. Always be pushing and pulling in directly opposite directions.
Remember, you only want to pull on the wrench head enough to eliminate the shearing force. You want the torque to be centered on the axis of the bolt.
You may already be doing this, but just one more thing I thought should be mentioned when talking about shearing off header bolts. The rear-most stud on my 258 was sheared off inside the head when I bought it. If there are any that I would recommend being extra careful with, it's that one. With the firewall right there, it was a real PITFA to get a drill square to the head.