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The original 1960 Shop Manual states:
Bolt-Pressure plate cover to flywheel:
5/16 -18: 18-25 ft-lbs
3/8 -18: 25-30 ft-lbs
My issue is, I have six 1/2 bolts holding the pressure plate to the flywheel. I'm not sure if those are the original bolts or not. I assume not, but figured I would check here for any thoughts on the subject. Thanks in advance.
Welcome to FTE. That doesn't sound as though the 1/2 bolts are original to the truck. Are they fine or coarse thread? Do you have the 4 Speed tranny? Here is a site that seems to understand torque to a deeper level than I do: Fastener Torque | Engineering Library
They recommend 42-64 for coarse and 52-77 for fine thread, without lubrication on the threads. Does the flywheel appear to be stock. I guess someone could have messed up the threads of one hole and then in effort to keep things balanced, drill them all out over sized?
One more thing, the 3/8-18 thread listed is not normal off the shelf stuff, probably some Ford thread just because they wanted to. Coarse 3/8 bolts are most often 16 threads.
spurredon, thanks for the information and the link. I did forget to mention it has a 4 speed with the in-line 6.
I'm going to assume the flywheel isn't stock, based on the "farm truck" mechanics I've come across since diving into other things. I did verify the threads as coarse, so I figured I will likely torque the bolts to an average foot pounds and go from there.
Just so we're clear, bolts are measured by the shank size, not the head size. I could be mistaken, but I'm guessing you're using a 1/2" wrench thinking you have a 1/2" bolt, when it's probably a 5/16. Typical 5/16" bolts will have a 1/2" head. I don't think there's enough area on the pressure plate or perhaps even the flywheel for a half inch hole and bolt to attach. A true 1/2" bolt typically will have a 3/4" head. Pressure plate bolts are special with a countersunk hole and a corresponding shouldered bolt, so you really want to make sure you have the right parts to prevent failure. If you don't have the correct pieces, I would highly recommend getting proper replacement parts.
If someone really did hog out the flywheel and pressure plate for true 1/2" bolts, you really should pitch the whole mess and start over. It would be dangerous and a disaster waiting to happen, and it could actually be deadly. Ask Don Garlits what happens to your feet when a clutch blows up. With the correct pressure plate bolts, and a good flywheel drilled with the right hole and good threads, I'd use a drop of blue locktite and torque to 25 lbs.
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