projectheaven

What are expansion plugs?

joe_padavano

They are also known as freeze plugs. These are the shallow cup-shaped metal plugs (sometimes steel and sometimes brass) that are pressed into the sand core holes in the block and heads. Since frozen coolant expands and pushes them out (hopefully before cracking the block) that's where the "expansion plug" and "freeze plug" nomenclature comes from.

projectheaven

oh ok. Makes since now.

Oldsmaniac

They were also called core plugs according to my shop teacher and as stated were there to simply plug the holes after casting the block. Although they sometimes can protect a block from freezing they were not designed to do so. This "protection" would be a by-product of design.

442garage

If you are in the process of replacing expansion plugs, freeze plugs, or core plugs, be sure that you get the right depth and diameter. I had to rebuild my motor because an engine builder used shallow freeze plugs that were not deep enough to seat properly. Dorman makes the proper one for Olds, do not use Pioneer brand!

wmachine

Actually, Joe, it was a dual design. The foundry does need openings for the water jacket core for the core support and to clean out the water jackets. In applications where a cored hole simply needs needs to be plugged, a core plug and/or welding up the hole would be done by the foundry. At some very early point in the development of water jacketed engine blocks, the freeze plug use of the those cored holes was recognized and has definitely been part of the game plan ever since. That's why the holes don't get permanent plugs.

wolfman98

I have always known them as freeze plugs up here in the great white north.It seems to me that in very cold areas many cars used block heaters that would be put in the block where a freeze plug was. when I lived in saskatchewan I had a 72 grand Prix 454 that had duel block heaters and still I had to add a circulation pump and battery blanket so it would start on those -45 degree mornings.

88 coupe

And the myth continues.

Norm

wmachine

So you say, Norm. Care to substantiate your claim like I did? I've been in the foundry business for 35 years. Your credentials?

88 coupe

You did not substantiate anything.

Do you have any evidence showing that "freeze" plugs actually work in the manner you suggested?

How many of those years were you involved with the type of engine castings we are discussing?

As I have said many times, I have no "credentials".

Can we assume that your 35 years of "experience" in the field would enable you to defend your position, without resorting to the "credentials" card?

Norm

wmachine

That's what I thought Norm. Nothing to substantiate you or your myth claim.
The word "expansion" as in "expansion plug" refers solely to the "freeze plug" aspect of its purpose, because "expansion" has absolutely nothing to do with the foundry casting making process.

88 coupe

And nothing to substantiate your "freeze plug" claim.

Any documentation to back that up?

No one said it did.

Norm

wmachine

Sorry Norm, I'm not going to spar with you. What has already been said speaks well enough for me.

88 coupe

Why am I not surprised?

Norm

88 coupe

Also, depending what region one was in, they were called casting plugs, or soft plugs.

Referencing Coldwar in post #11, the correct name is, expansion plugs. It has nothing to do with freezing water, and everything to do with its design and intended use: Expanding and contracting, in order to maintain an air or watertight seal with the dissimilar metal around the hole it plugged.

This is the way I learned it.

Without documentation it is not possible for us to know why it was done that way, instead of having them closed at the foundry. Might have been cheaper to do it, as part of the machine operations.

If I was interested in learning why it was done that way, I would not be consulting a “foundry worker” who had nothing to do with the design of the product. Instead, I would seek the engineer who designed it, if not one who was equally qualified, who could could explain the principles behind the decision.

I think your use of “sometimes” is a bit of an exaggeration but, unfortunately, I do not have any “credentials” to base my opinion on.

Has this ever been documented? Or is it based on several generations of folklore?

Norm

Oldsguy

Chill guys, nobody else cares....

wolfman98

I do not know what the original intention of these" plugs " were but I spent 13 years living in saskatchewan which was a very cold climate over the winter months , not unlike North or South Dakota Minnisota etc. Many car dealers would install the block heaters on the new car when or before it was purchased. In northren climates having an expanssion plug would make sense as the block would go from very cold to hot quickly., the block heaters would have been designed sometime afterwards to help with very cold morning starting. I know that my big block did not like -45 or -50 mornings. I remember having a 79 Park Avenue while there and it had a plush interior with soft seats. On a -45 degree morning when you first jumped into the car to start it it was like sitting on a rock. it was that cold that the seats would freeze as hard as a rock. They would issue warnings that exposed skin would freeze in 30 seconds or less. if the wind was blowing it could reach a wind chill of -70. I guess you would have to experience it first hand to appreciate it , as I did the first winter I went out there which turned out to be one of the coldest over the previous 50 years. Most workplaces had parking lots with posts containing plugins cause if you did not plug your car in while you were working then it would not start after work.

wolfman98

As far as I know there was nothing changed on the cars and I just got the recommended brake fluid from the shelf. On really cold mornings I would go out and start the car then run back in the house for 15 or 20 minutes.