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Posted by Clint Dixon [74.206.63.42] on Tuesday, August 21, 2012 at 19:13:02 :
I have been reading the posts about your bolts failing on your front engine mount.
If I am remembering correctly, this engine is the one in your truck that has the swivel frame? If so, I am not so sure that frame twist caused the bolts to fail. The swivel should allow the two frame sections to remain straight and without twist unless you have maxed the swivel out against hard stops, and then caused the two short sections to twist further.
I believe you mentioned that the mount bolted to the engine block with a 1/4 inch thick timing cover sandwiched in between? If this is the case, I can see why the bolts sheared. The engine mount should have been designed to fit flat and tight against the engine block, with nothing sandwiched in between. The mount should also have been doweled to the engine block. The dowels would take most of the load off of the bolts. I assume the bolt holes through the mount were a clearance fit to the hardware - not an interference press fit as you would find for dowels? The engine block would be drilled and reamed for slip fit to the dowels as the holes would be blind holes - not passing through into the crankcase. A 1/4 inch thick spacer between a plate with clearance holes and an engine block with tapped holes would only aggravate the problem even more as the holes through it probably have even more clearance to the hardware. You were in effect cantilevering the engine out there on the hardware and creating a natural sheering effect.
All in all, not good to have the surface between the mount and engine block in a vertical orientation. That is why the side mounts work better - not truly horizontal, but not vertical either.
Can't say for sure without personally inspecting the parts. Just adding something to think about.
Junior
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