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Need some direction .. my 1940 pick up truck im running a 1951 216. When i start my truck im getting a big sqeeling noise after about 45 seconds it goes away and comes back somewhat when i step on the gas for a high idle. I tried swaping fan belts to a smaller with 3/8 and it got a little better but didnt completly go away. Heres what i noticed my water pump pully seems to wobble a lil bit but then starts to spin staight and noise goes away. Is this noise my water pump bearings? I tugged on the water pump pulley and it doesnt seem to be loose. and if it was my water pump bearings why does it go away after a short while. Its not an easy job to replace water pump so i need some advise or someones expertise opinion. Also im really confused on what size pulleys i have. The 1951 216 does it come with a 5/8 pully ? And what width size belt do i use ? The belts never say 5/8 or 3/8 in example the belt i just installed is 13/32 W x 42 5/8 L and the one i was using before that was .53 W x 42 1/2 L so whats the correct size for 5/8 pullys which i think i have.

As far as fan belt I have a 5/8 on my truck. It was on 1950 216 and now on a 1957 235. I used my 216 water pump/pulley , generator, and harmonic balancer .
Here is a picture and specs for the belt. Are all of your pulley sizes the same? Water pump, generator or alternator, and balancer?
That is a Napa belt fyi
How loose or tight is the belt?

I believe the pullys are the same . I purchased a 5/8 pully for my alternator becuse i assumed the pullys on engine and water pump were 5/8. The belt is tight but i tried running it a lil loose and tight still had the sqeeking noise

Start with the basics and Confirm each pulley size. Do not assume. You are describing the slipping fan belt.
Also, changing the water pump on a 216 is not a difficult task. Hopefully you don't need to.

When u say i am describing the slipping fan noise . Are you saying you think its just the fan belt making the noise ? I say its difficult to change water pump because on my truck i need to remove almost the whole front end including the hood to get too water pump. Any pointers on how to exactly determine my pully sizes ? When i measure do i measure rim to rim of pully and it should be 5/8 ?

Yes, descibing fan belt noise. Here are the two different pulley sizes ( from a generator) . Sorry, just saw a 1940 truck, I understand .
On the picture of both, the 5/8 is on right 3/8 on left.
Let me know if this helps. The 3/8 (smaller one) comes almost to a "V" point at bottom. The 5/8 does not if you can see that in the pictures.

Yes it helped alot. I got 5/8 belt pullys .. question i dont have a 5/8 belt seems i never did even with the two diffrent belts i used they were 13/32 which is 3/8 pretty much and .52 which is like 1/2 .. is it pretty obvious that this is the problem . Using a true 5/8 belt should be the fix ?

I would think so. A 3/8 belt really does'nt fit in the 5/8 groove. I would think it's slipping and then finally grabs from tension? Has it always been set up that way or?
Depending on your actual pulley's and set up the Napa one might work?? I can check the actual belt lengh tomorrow if you need.
Todd

No help on chasing the squealing, after checking belt alignment to generator and damper I would probably get spray belt dressing and hose it down, then I would know if it’s the belt᠁᠁and then change it out no matter what.
Don’t know the under hood space on your 1940 but on my 46 w/235:it's not exactly roomy, i swapped water pump out without removing the radiator, center hinged hood, or anything other than the generator᠁.just took a little patience.

Chuck

Thanks chuck ya i been kind of looking around and it might be doable just no sure if the patience outways the effort to just remove whats in front of water pump idk i will have to decide once i eliminate belt forsure᠁ Todd i landed ordering the napa belt that measures 19/32 X 44 .. i looked up your belt number and got the specs so im good on that but thanks anyways you been a great help .. ill will keep you all posted

You say the waterpump pulley wobbles some on start up and then goes away. Take the belt off, grab the fan and see if it wobbles any by hand. Any wobble at any time is concerning. Plus... a 3/8 belt will bottom out on a 5/8 pulley.

While you have the belt off, check your harmonic balancer to make sure the sheave is still vulcanized to the rubber damper.

I recently had a squealing/squeaking noise on another car that I attributed to the water pump. It turned out that the sheave on the crankshaft balancer had become unstuck from the rubber that is sandwiched between the pulley hub and the sheave.

It would squeal on startup and then catch after a little while.

Per Otto: Check the sheave on the balancer and check for a failed bearing in the pump. I have seen the same sheave problem on other engines (Ford) and it's a tough problem to diagnose and often the last thing checked.

My former next door neighbor had a 51 car with a 261 with 5/8 crank and generator pulleys but a 3/8 water pump pulley. He could not be convinced that the application listing for 3/8 belts for that car was wrong. He ended up buying another pump with a pressed on 216 sheave so the 3/8 belt would fit. Not only did it slip in the crank shiv but it threw a fan blade through the hood. Made a nice clean louver. I eventually ended up with that pump after I gave him a 5/8 truck pulley for the factory water pump and convinced him that since it was a truck engine he should go with the truck application listing. This whole process took a couple of years, meanwhile the engine would over heat if he drove it out of the neighborhood. I think it eventually cracked the head from overheating.

Otto can you explain a liltle more on where or what the sheave is and how to check if it is still vulcanized to the rubber damper ? Sorry i know a little but never got into the pulley system enough to know what your really saying. Im going to replace belt with a 5/8 but want to check all that you and everyone else jus mentioned.

I think i got it .. i went to go look around at the crankshaft pulley to see what the sheave could possibly be.. i tugged on the fan which had no concerning wobble. I spun the fan by hand and could here the squeal .. i started the truck snd squeal was there i sprayed the water pump pulley with water and it immediately went away comes back once water drys up i spray again and it goes away. The belt seems to be slipping on pulley .. the fan pulley even just spins by hand way to easy slipping off belt. I have belt really tight so it has to be the width size of belt.. waiting on 5/8 belt had to order it no auto store carried a 5/8 x 44 i tried a 43 but could not get it around pulley .. belt teeth kept it from going on so i have go a little bigger on belt size..

The sheave is the term for the grooved portion of the pulley. It's basically a ring with a belt groove in it that is bonded to the half inch ring of rubber which , in turn, is bonded to the hub of the pulley.

It's possible that the water pump bearing is going bad causing excess strain and belt slipping. If your belt is adjusted correctly and it still squeals, I would check the water pump more closely. All the water is doing is lubricating the pulley/belt interface.
A bushing type bearing can squeal or rattle if it has excess clearance causing the shaft to bounce back and forth inside the bearing bore. That's usually intermittent until the shaft centers itself and stops bouncing.
You may be looking at replacing your water pump if it has too much turning resistance. Maybe a visit to the parts store to compare with a new/rebuilt water pump. They should let you check one prior to purchase, but you may ultimately need to replace it.

The belt should never contact the bottom of the sheave. If it does, the sides of the belt are not doing their job and the belt will slip (and hopefully make noise so you will know something is wrong).

Try feeding something small like a piece of solid (not stranded) 18 gauge wire or maybe a flattened soda straw between the bottom of the belt and the pulley. If it will slide between them the belt is not riding on the bottom of the sheave (that is good). If you can't, I'd recommend get a one step wider belt.

Attached a quick guide for belts
Maybe it will help select the right belt

1950 Chevy used B belt
By 1953 they changed to A belt
That’s why the early water pumps come with two different pulley options
-s

The harmonic damper rubber in a 216/235/261 is not vulcanized. It is simply what looks like a rubber vinyl record sandwiched between two pieces of steel discs, held in place by rivets. I had to fix one that I dropped, causing a horrible wobble. I drilled out all of the rivets with a drill bit which coincidentally made a hole which a 10 mm bolt shoulder made a snug fit inside. I bolted it back together and chucked the snout in a lathe and strategically tightened the nuts, maintaining trueness until all of the nuts were securely tightened. This process is applying even pressure on the rubber disc. If the pessure is applied unevenly, The balancer will wobble.
All of this is trivial to the OP's need for a new waterpump and the correct belt, but sometimes I get carried away.

Its fixed i installed the new napa belt 2522434 19/32 x 44 the squeel is gone .. the whole problem was i was never using a 5/8 belt .. thanks for all your help greatly appreciated.. one more quick question i had trouble starting my truck today with the push start. I had to slam on it hard to get it too turn over .. is that a sign of bad starter or something wearing down on the push rod that hits the starter button ?

Once engaged, did it turn over and start up normally?

If so, yes, check the linkage, etc. where the lever contacts the starter button. One trick is to put a bottle cap over the starter button if things are worn away. Take out the rubber, seal, first.

Yes it started normally once i slammed on the starter button .. but a normal step on the starter button i dont even get a sound..

It seems like maybe the spring on your button is collapsed or broken or the linkage has some slop in it or something.

Check all that out.

You can work the starter rod/lever by hand under there and see what happens when it contacts the button.

Ok ill check all that out thanks