21 Stud block question
 

I have what appears to be a bare 21 stud NORS service block. Are there any identifying numbers in the casting. There is large 38 cast into an area inside the block. See photo.
I have never seen a block where the interior water passages looked new like these. Is there a process to clean them to the point they look new with no rust damage. Even the thin casting flash in the water passages looks brand new.
Also, do all 21 stud blocks have core or freeze plugs in the pans rails. See photo.
Those plugs might have saved all the 24 studs blocks I have seen with cracked pan rails from freezing.

Re: 21 Stud block question
 

Never saw that freeze plug set up before. Hope someone can
tell us the story.

Re: 21 Stud block question
 

All of the 21 studs have the welsh plugs. There is a slight step in the size of the holes for the plugs and the plugs rest on the step and can be punched to lock them in place at the step. It is possible there were problems with the steps on your block and the block was drilled out to accept the freeze plugs so there are no leaks.

Re: 21 Stud block question
 

But if the oil pan is attached they cannot function as freeze plugs.

Re: 21 Stud block question
 

Good observation David.

Re: 21 Stud block question
 

Core plugs

Re: 21 Stud block question
 

They are core plugs. Used solely for the purpose of supporting the cores in the sand casting process. Once cast and the sand cleared, the holes are plugged. Threaded fitting were used in the 19th century. The "Welch brothers " had a better-cheaper idea for filling the holes in the 20th century.
No such thing as a "freeze plug".

Re: 21 Stud block question
 

Thank you all. Welch plug it is, and with the pan on, that's all it is. Anyone have an idea of how the water passages could look like new. Is there some process I am not familiar with.

Re: 21 Stud block question
 

Not all the 21 stud blocks had core/welch plugs in the pan rail; I have one in my collection that has none!

Re: 21 Stud block question
 

I have come across two of those blocks with the 'super clean' water jackets. One other feature they have is the third hole drilled and tapped at rear of block for oil cooler. They seem to be a very high nickel casting. One of those blocks came out of a bren gun carrier; very low mileage, it still had V8 branded sparkplugs, never seen those before either....anyway, my experience with these blocks is that they crack big time!! In both instances, these blocks have cracked in numerous weird places, neither block was abused. I now avoid them. You think when you find one, 'wow! what a great block; no corrosion, you spend lots of money machining them up, then, down the track you start getting water into cylinders etc. Gets somewhat demoralising...your experience may differ, for your sake I hope so, good luck

Re: 21 Stud block question
 

Stripping will leave a block looking as new as far as no rust, scale or core sand.
High quality engine builders have been doing it since it was invented.
It is the only system that will get scale out of the bottom of water jackets.

Re: 21 Stud block question
 

Bake, blast and shake processes, when done correctly, leave a cleanly blasted interior and exterior block finish. A glance of the pictures here seem to lend themselves to indicate that is what was done to the pictured block.

Re: 21 Stud block question
 

Correct I have one of each.. The pilot block does not.

Re: 21 Stud block question
 

I've done it with phosphoric acid.

Re: 21 Stud block question
 

It's not good to use phosphoric acid on cast iron as it removes carbon from the grain structure. Better to use caustic.

Re: 21 Stud block question
 

What is caustic?

Re: 21 Stud block question
 

Caustic Soda (Sodium Hydroxide) is what is used in "hot tanks". But, it doesn't dissolve rust. It may loosen rust though.

Re: 21 Stud block question
 

Thank you for the info. I have 59L block that went through the bake, blast & shake process at one machine shop, and it still had a loft of crust in the water jackets. I elected to move the machine work to another shop for unrelated reasons, and they hand blasted the water jackets to clean them out. It didn't look as good as this block though.

This block has the 2 standard threaded holes in the bell housing boss, one for the oil pressure sender and the other for ? See photo. I take it there were oil filters for the 21 stud.

Re: 21 Stud block question
 

Those two holes are present from the beginning of V8 engine production, which predates Ford adopting an oil pressure gauge and an optional oil filter by three model years. In the '32-'34 versions those holes are filled with square-head pipe plugs as their purpose reaches back to the machining of the oil passages within the block.

Re: 21 Stud block question
 

I get it, they were for drilling out the oil gallery. Thank you.