I was asked a question today that I couldn't answer without some input from you experts here.....
Can the wrist pin bolts be replaced with a regular (grade 5?) bolt? There is a shoulder on the bolt that sits in the pin cut out - is it critical that this is a shoulder and not threaded?
My thinking is replace it with a good original (which I have no spares of - hence the question).
You could but you need to drill a hole for the cotter pin. The vendors should have repro ones. Is there a problem with the repro's?
I heard that the repros are really brittle? Apparently they are snapping off. I haven't even had a repro one in my hand, so not sure how true it is.
I used repro pin bolts on three engines the last two years and didn't have any problems.
The shoulder is needed to prevent the piston pin to turn and will center the pin in the middle of the piston. A full threaded bolt is a little smaller in diameter and the threaded part is more fragile. As Ted said you also need to drill a hole for the cotter pin in the bolt head.
My opinion it is better to use a good original than a regular 5 grade bolt.
Thanks for the info. I will order some repros for him if he can't find any originals. I am wondering if the ones that broke were tightened too much.
Oiling threads causes false torque readings:
Ralph - that is what I was thinking. Oiled the threads than started cranking on them with a torque wrench. I was also told by an old timer to leave the toruqe wrench on the bench and just get them good and snug.
You don't need a torque wrench. There's no correct torque for any bolt on a Model T.
Be careful not to overtighten wrist pin bolts, its very easy to strip them.
If you don't oil the threads on any bolt, you take a chance on galling the threads.
Use the old bolts if they are any good, or find some replacement originals.
Forget the cotter pins, use new lock washers, and torque to 30 Foot Pounds.
Cotter pins will not hold the bolt from turning back and forth, and can wear.
I made a hundred or more and am willing to share if you need a set. Ken
I sent you a message.
I am in the process of stripping an engine and there are bits of wire throughout the motor. The only place they could have come from is wire on the wrist pin bolts. I was taught to use cotter pins, clearly other folks were not.
I have used old bolts except on one occasion when I bought a new set from Snyders, no complaints that I know about.
On reflection I don't think the cotter pins could come loose or break, I have never seen a partial one on the pin bolt, but I have seen several like this engine (including my first rebuild) where the wire has broken. I suppose the forces involved are huge and repetitive, the cotter pins seem to withstand it much better.
My bolts came also from Snyders. For the cotter pins just use the right one and you will see they are to long and will hold the bolts from turning.
The right bolts have a higher head and are easier to get your wrench on.
Keep it save
About the torque.
40 Years ago, as I started working as a mechanic, an old timer told me: Crank you bolts and stop 1/2 turn before the bolt breaks or galling the threads. Now 40 years later I can feel when a bolt is going to break or the threads are running of.
I only use a torque wrench on the head bolts.
I am thinking: Isn't it Independence day in the USA to day??
Enjoy the day
Folks like to blame the bolts when in fact the are just heavy handed and don't understand.
Sorry for the soapbox, but as Andre says, there is tight enough and there is too tight...hardly ever do we hear too loose.
The first 'foible' is that most tables are based on something called 'dry' and that really does mean medicinal dry, something you never find in out of the box bolts.
The second foible is that most out of the box torque wrenches are going to be 'off' by about 10-12% to begin with and you can add about another 10% the first time you drop it.
The third foible is that most don't understand fastener technology and believe that when they go to a grade 3 or a grade 5 fastener they have to up the ante! Typically, the majority of Ford items were based on what is equal to Grade 2 technology today.
No need to learn the math, but the torque developed has a formula to get back to clamping force. Clamping force is what you need and probably Ford based all of their calculations on clamping force. You take something that (say) was meant to take 32-34 ft-lb if we use a torque reference, and dump 50-52 ft.lb. on it, you ARE using near 50% more clamping force than Ford ever intended to be used. (Heads do cause the imponderable because once you ante up the compression ratio you need to add that much additional 'clamping force' to the head bolts to make it behave the same as originally intended)
I know that no one ever wants to hear it, I know that the present day mentality is to torque wrench everything, but there are too many variables to try and table a torque value.
Ford 'proabably' used a lightly oiled bolt and not a dry bolt, Ford used for the most part Grade 2 bolts based on the original bolt specs (you just can't harden the material they used to get the higher spec requirements of the other Grades). Ford DID start to migrate to a material that would be Grade 3 rated material probably about the time when Rouge came on line---but...since they didn't change the geometry of the Ford tool list sizes, you can rest assured that they expected the same prior torque or in reality the same prior 'clamp load' and this change in material was probably one of economics and not strength.
Want to have fun with your own 'Z' tools? Figure the average 'pull' of a man to be around 30-40# of pull. The point just before you have to put upper body twist into it or use your other hand for leverage. Measure from the center of the claw to the center of the grab point and change it to feet. Multiply the two together. B-I-N-G-O ...THAT's the 'clamp force' that Ford was looking for in the first place.
Yeah, I know...I'm a broken record on this...but when I rebuild something I don't snap bolts, I don't strip threads, they don't come loose, and I don't have leaks. I know...I'm just lucky
You aren't Lucky, you just know how to do it.
Lube the bolt, and it will back off that much easier. That's probably why re-torquing head bolts is called for.
Did the bolts work out for you?
I have posted this before but I wish dry torque charts were not published. Dry means chemically or mechanically stripping a bolt, and the nut or threaded part, of ALL lubricants. If you actually had a dry bolt you would lubricate it just by picking it up by the threads with your bare hands. Dry Torque is NASA stuff. Always use wet torque values and be aware that different lubricants will affect the final torque values.
I had sent you an email awhile ago - sorry if you didn't get it, my emails have been bouncing around lately.
Bolts worked great! Thanks again!