The Stovebolt Site Forums The Shop Area General Truck Talk Guess that bolt

The last time my dad and I were changing fluids on the WD 45 Allis my pops couldn't remember the socket size for the oil plug and he danced his fingers around and said " get on that thing" meaning, search the web. I've cleaned up all the bolts, replacing most, but not sure where some go. Have new pressure plate,clutch, bell, engine supports.... this is a master class if you know these. I wish I would have been there for engine removal but if you can take a guess I appreciate it.1953 3100

When you're putting it back together, just match the threads and carefully screw the longer ones in place. If they bottom before the head hits, then use a shorter one.
If you have any left over, just toss them in a old coffee can, the traditional container for leftover bolts.

Hard to tell from your pics on size, but those may be for the rear engine mount. The shorter ones may screw into threaded holes in the bell housing to hold the mount in place, and the longer one down thru the mount bracket and the crossmember with lockwasher and nut on the bottom. That's a WAG for sure.

I’m sure some engineers will baulk at this, but I remember the engineers saying, at the large heavy equipment manufacturer I worked at for 37 years, the bolt hole depth needed to be at least twice the bolt diameter to get the proper torqued stretch. Beyond that didn’t add any holding power.

I imagine that might be valid for critical connections, but I've never heard that before. I have heard that bolts need to extend three threads past a nut, which doesn't really add much to strength, IMO, but is just to make sure all the threads in the nut are fully engaged.

Extending past a normal thickness nut a bit is required for maximum strength
I would need a white board to explain it best
You can do experiments in a tension puller to prove it
But it’s remarkably calculatable detail
There is a inverted cone of unsupported material along the shear surface in the center of the bolt face at the top of the bolt when it’s flush
This lack of material means the top most threads in the nut have less shear material so they are engaged in threads but they are not able to fully benefit from the bolt bulk which will deform and pull away in a cone shape not a flat surface shape
Flats happen from stress cracks and defects
Pulling metal samples to failure use to be a standard engineering class in like 2nd year or so and was very non intuitive
Half the point of the lab experiments is to drive home how something so simple has phds and years of research behind it and is not intuitive at all
The material failure modes are applicable to many other situations not only bolts and helps people think more critically and ask the right questions - what don’t I know about this and maybe it’s not at all the way I think it is.
-s

Good points. Kind of way detailed, but still good. I would agree with loading to failure, but most bolted connections on our trucks are way over-designed ( or I should say have an adequate safety factor. ) I would say that a nut and bolt connection will more likely fail at the thread root somewhere between the nut and the bolt head if pulled to failure, even if the bolt threads didn't extend past flush with the nut. Full disclosure: I have not done that test.

I spent a week or more in a classroom setting teaching my auto mechanics students to stretch/break bolts threaded into a tool steel stress plate. It was better to let them experience a bolt failure under controlled conditions than to have an "OOPS" moment on a shop project! Then they got to remove the broken off stub with a lefthanded drill bit or an EZ-out.
Jerry

I have the 2 side bolt that affix the rear engine mount to the bell/clutch housing. does anyone know the third bolt used that goes into the cross framing?
the drawing i have says 1/2-13x 3 1/2 but that seems way long. Doesn't the bolt pass thru the U channel and into the bracket. 1953 1/2 ton 3100- thanks

In my bag marked "REAR ENGINE MOUNT BOLTS", I have four 7/16 coarse thread x 1-1/4" bolts with lock washers that go into the bell housing and two 7/16 x 1 fine thread bolts and nuts that go thru the crossmember. I believe your engine mount should be the same as my '51.

nice-thanks bolts go up through cross frame and split washer- that's what my drawing shows, but its says all models and there is a sleeve that the bolt runs through. so that
is not for the 3100. great work on your truck.

weewilly,

Is the attached pic below (taken from my 1947-54 FAM) the diagram you are referring to???

If your rear mount is like this, that long bolt needs to have the sleeve (spacer) and the "bolt lock" plate to install/secure the mount and bellhousing correctly to the crossmember.

If my info is inaccurate, am sure fellow Bolters with more knowledge will come along and offer more info.

Dan

Here is how the mounts were on when I received the parts back after engine removal. Did not have bolt sleeves or long bolts in bucket of hardware, but had the 2 on each side of the bell.I'll guess the mounts are upside down and the sleeves and 3 1/2 bolts are needed. What would be the purpose of the thick rubber rands on the side if they aren't touching the frame.

My rear mounts don't look like the FAM (which is 53-54 stuff). Here's a couple of pics.

[On edit]weewilly, Your mounts look like mine, and just need a short bolt thru the bottom of the mount and the frame. The rubber for vibration isolation is between the metal parts that bolt to the bell housing and the crossmember. Added another pic of the driver's side.

Perfect. Thanks for the pics, thanks to all for the guidance. Lots of little bell housing casting changes from the 1953 GM 3701433

The 1954-up bell housing has a redesigned mount and a different angle cast into the housing (around 45 degrees). That's the one that requires the long bolts and sleeves. It also needs a different crossmember with angled, not flat mating surfaces for the mounts. The later style mount is far less likely to deteriorate and separate than the vertical ones.
Jerry