How hard should I torque the transmission drive plate bolts?
Ford never issued any torque specifications for Model T's, the method used then was to use a proper length of the tool so the torque got about right for a medium strong man = not very precise, but it usually worked.
I'm only using my torque wrench for the head bolts, the main and rod bearings and the transmission/flywheel bolts in the engine. You can use loctite and wire the bolts together to make sure they won't fall off.
It's common to find cracks in the 26/27 brake drums where these bolts goes - such a brake drum sholdn't be used. There are good ones out there - I've found a few. Reverse drums without cracks is harder to find. A reproduction drum is another more expensive option.
Just tighten the bolts. Sheesh.
..And tighten them in a cross wise pattern like all assemblies with several bolts
Here's a link to a site with generic torque values for various english size bolts:
The MTFCA DVD (Restoring the Transmission II)I watched suggested 35-40 lbs. At 35lbs two of them stripped. I just wanted to make sure I didn't strip them again.
Have you checked your torque wrench? 30-35 is about all an average person can get with a regular socket and 3/8" ratchet wrench or box wench. Torque specs didn't exist in the Model T era so any specs suggested are approximate to say the least. And if the bolts were wet (lube, antiseize, etc.), the spec should be reduced drastically.
Reminds me of an event with the B.I.L. I was helping him install a trailer hitch on his truck. The hardware was all grade-8 9/16" and made in USA. All he had was a 1/2" ratchet wrench and appropriate sockets. They're what, 10" long? He asked how tight they should be and I said; "As tight as you can get them". That was a mistake! I didn't take into account his stature and strength. He promptly twisted a bolt in two. I tighten the rest and had him put another 1/16 turn on them.
If you look at a set of wrenches 3/8 to 1 inch they come in different lengths. That is the built in torque setting. Without going out to measure I think the Ford wrench for the rod nuts is something like 7 to 8 inches. The average man pulling that wrench can only pull it so tight, which is about 35 LBs. A 9/16 wrench (normal type not special) is about 6 inches, that's how tight you want to go. Even using a normal length 1/2 inch socket wrench might be too much torque unless you choke up on the handle.
35-40 lbs is too tight. Overtightening these bolts risks cracking the bosses that hold the internal threads, at least on the earlier brake drum. I snug them up with a thin wall socket and 3/8" ratchet. If I had to put a value on the torque, I'd say 25 ft lbs. maybe a bit more.
Thanks. I thought 35lbs. felt too tight. I should have followed my feeling.
Don't confuse bolt head size with the nominal size given for bolts. A 9/16" bolt usually requires a 13/16" wrench size for the head. A 9/16" wrench will not fit a 9/16" bolt. A 9/16" wrench is for a 3/8" bolt. (Standard sizes)
I'm pretty certain the factory used speed wrenches during assembly. They're shown in use throughout other assembly operations in many factory photos. About the most you can get on this type of wrench is about 20-25 ft/lbs. That's what I would use. They won't come loose since they're supposed to be wired together in pairs.
For what it is worth. I just first read the question. My very first thought was "about 20 pounds". I do not know who wrote that book, and hope I do not offend anyone too much? But the threads in the drum are cast iron and not nearly as strong as a good steel. 35 to 40 sounds good for a good quality steel into steel and solid compression torque. My "first thought" may be a little low. But all I have ever done on those bolts is a good hard pull with a short handled wrench. Then wire the bolt heads reasonably well.
Drive carefully, and enjoy, W2
Sure it wasn't stated as inch/lbs?
Just to clear up, I meant 35 for the Ford rod nut wrench not the 6 inch 9/16. 20 ish sounds about right.
Richard is right, NOT under 25 foot pounds, and not over 30, and oil the threads.
Thanks Khonkne, Great low tech way to measure between pulley and drive plate!