The Stovebolt Site Forums The Parking Lot Panels 'N Burbs Radiator core support

I think I know how this goes but just want to make sure. Working on my 52 GMC Sub and ready to install radiator so I can fire up the 5.3. I'm not exactly sure which way the squared u-bolt with springs, flat bars, and rubber pad are installed. U-bolt and springs up inside the support facing down or hanging down from the crossmember with nuts on the inside of support? Do I make myself clear? I'm thinking it is the first way with the u-bolt and springs showing inside the support. Also I'm not sure how thick the rubber pad should be. Been reading the hood install post and it says you need to maybe shim the support.

Thanks, Richard

Richard,
This is the set-up on my 46 so it is probably very similar to yours. The main difference is I could not locate the correct U-bolt so I used 2 bolts instead. In your case, the U-bolt goes through the metal bracket as a way to level the curve of the U-bolt where it goes through the radiator frame.
Hope this helps you.
Harold

Thanks Harold,
So the springs are under the crossmember. How did you decide to use 2 rubber pads? How much compression on the springs?

Thanks again

1952 (47-54) GMC radiator support bracket and springs

But, the nuts on that replacement part are probably not like the original nuts.

U-bolt through the top with a plate or two (whatever is not used as shims). Under radiator support is the rubber isolation pad and whatever shims are needed for alignment of the front sheet metal. Then through frame cross member with a spring, large washer and Marsden nut on each down leg of the u-bolt put on from the bottom. You want to lightly compress the spring. Not too light but leave some room for things to move when the truck flexes going down the road. The Marsden nuts are important as they are a lock nut which is hard to use a lock washer against a spring.

You don't want to use a Marsden nut, which is free-running until tight. It wouldn't stay tight with just the spring tension. A prevailing torque nut (interference fit on the threads) or Nylock nut should be used. Or drill the u-bolt for cotter pins and use castle nuts.

Maybe I am using the wrong term for the nut which is very stiff to turn. This is what GMC put on the trucks. The 47 pick up was hard to get a pic of the nut but you can see it matches the nut which I am holding in the next pic. That came from the 47 panel as did the rest of the parts pictured. The 48 is not here but I am positive it has the same nuts holding it together. I am sure the nylock nuts will work. I guess I assumed that everybody keeps, catalogs and saves these parts like I do

Marsden is a specific type of self locking nut. What you've pictured is a type of prevailing torque nut. There are a bunch of types of them.On yours the split conical shaped part is bent inward to tighten against the threads.
When you posted the Marsden nut reference, I'd never heard of it so had to look it up.

I dimly recall that my 54/55 2-ton GMC's radiator housing looked like the attached image (with a Marsden-style nut?).

Thanks Kevin. I was using the wrong name. I read through the fine print of the manual and they are referred to as special locking nuts. As such, any sufficient lock nut will work. I presume that there would be no torque rating to let you know how tight to go due to the lock nut drag?

Correct. Prevailing torque nuts are the same “feel” as soon as all threads are engaged. Some look like normal nuts but have a couple divots pressed into two flats to deform the threads. The ones with the conical split section are probably better to use as they have some springyness to avoid deforming the bolt threads and are more reusable.

Again, thanks all. That picture was just what the Dr ordered.

Richard

As Kevin says a Marsden nut is not what you want to use. It needs to be tightened to lock. You want a prevailing torque/deformed thread lock nut. So you can "adjust" the spring tension. Make sure you use the same grade nut as the Ubolt. Which is probably Gr 5. The American Classic Truck unit has incorrect hardware. They show a free running nut with lock washer.
The TF (55.2-59) Blue Chip GMC trucks use the same style spring loaded attachment. May be exactly the same. I have a set to look at.

A Marsden nut does "look like" a deformed thread nut.

Be sure your ubolt threads are nice and clean and that a regular test nut goes on OK.

Harold's idea is just fine, I myself don't like nylon locking nuts.