FYI - Core (Freeze) Plugs

[James_Douglas]

Hi All,

 

Have been ill, then family death, then...

 

I have not posted in a while.  I am starting to work on a replacement block for the '49 Desoto.  One thing I had trouble with, if you read the decade old archives, is the core plugs.

 

On the '47 I used brass and they blew out.  Turns out the Dorman brass plugs were 0.02 smaller in diameter than the steel ones.  I also have had issues with the steel ones leaking over time and I am sure it is because getting a proper hammer blow on the plugs with the engine in place was not optimum.

 

So, on the 1949 engine I want to do it once and never have to do it again.

 

To that end, I contacted a company here in California that makes, among other things, core plugs.  They have them in steel, brass, and stainless steel.  They also have the engineering staff that knows the "correct way" to install them.

 

I am going to have my general machine shop, not my auto machine shop, bore the core plug holes a few thousands over from their current size (1.631") to some larger and perfectly round size.  I will also make the "correct tool" for installing them. That tool does not press directly on the center portion of the plug and it has a flange that bottoms on the outside of the block so you cannot pound them totally flat.

 

One thing I learned from them is that you are NOT supposed to hit them in the middle if the hammer on the plug is anything less than the entire size of the plug!  If the center is flat they will eventually leak at the outside.  You are supposed to press them in to something like 30% of the original dome height and not depress the center of the dome.

 

Once I get the done, I will post photos of everything for those that are interested.  Also, I may have to spend $200 for 100 plugs if they are custom sized.  I will use their stainless steel ones unless they tell me otherwise. I may have a couple left over...

 

I hope everyone is well. 

 

Best, James

[Mark D]

Glad to have you back. Sorry to hear about your troubles. I've always wondered about freeze plug removal and replacement. Look forward to seeing the photos.

[captden29]

James, you can also use the dorman plug that goes on with a wrench or socket. part # 568 010. I used them on my 265 flathead and they have been in about 4 years, no leaks. very easy installation. it has a blowout pressure of 300 psi and can be a permanent installation. good to carry one as a spare. about $5 each at most auto parts stores. they will not look as nice as what you are doing but they work.    capt den

[Plymouthy Adams]

Everyone else seemingly has had no problem with the purchase, installation and enjoy leak free service with the stock Dorman over the counter core plug for these engines.  Is all this truly necessary?  I believe you generally hit the nail on the head with proper installation being easily accomplished when engine is out of the bay...something you have stated as already handled.  I think purchasing a freeze plug installation tool would be the better money spent.

[Dodgeb4ya]

I use a heavy flat blunt driver... never have had a failure with these flathead core plugs.

I use a tiny amount of JB weld if the plug counter bore is pitted.

Some pics....

[James_Douglas]

I think a lot of it has to do with the condition of the block.  I the case of the 1947 that block was very clean in that it was acid dipped to remove all the rust.  I think a previous owner had "cleaned" the holes and may have made them a hair larger.  When I used the Dorman brass plugs everything looked very good.  When I started to run the engine hard after break in the brass plugs started to blow out.

 

After months of trying to figure it out we measured the brass plugs versus the steel one.  All Dorman.  What I found was that the brass plugs were a couple of thousands smaller in OD than the steel. 

 

The problem in my engine bay is there is no way to properly hit the plug with the fenders in.  I got them in and I had to put a little JB weld on them to make sure they did not move.  This has worked but it was a pain in the ass.  Also, I have had one other plug leak a bit, but that one was OK to get to and I replaced it.

 

The 1949 Engine bay is MUCH tighter than the 1948 and earlier models.  Keller's smaller on the outside and more room on the inside 1949's! 

 

I know of some people that have never had an problem with the plugs and I know some people that have a lot of problems with them in the flathead's.  I also have seen a LOT of casting differences in the flatheads as far as quality is concerned.  This '49 block was not nearly as good a casting as the '47 block or the failed '49 it is to replace.

 

So, I want to make sure that I do not have any issues.  To that end, as I said above, I wanted to seek out the people who engineer the plugs and find out what is the engineering behind them as opposed to the "normal" conventional wisdom on installing them. 

 

I will make sure that the interference fit is right at the minimum block ID and the maximum plug OD before they are pressed down.  Using the correct tool with the flange.

 

Also, stainless steel plugs would be nice.

 

James

[James_Douglas]

I am talking with a place in LA to make me a set of stainless steel core plugs. I went digging in the archives as I know that I posted some stuff on this about 10 years ago when I had the brass ones blow out....and yes they were installed correctly.

 

Don measured a set he had and they were the same brass and steel.  I have a set still that are about 10 Thou different.  Also, in the Dorman Catalog they show as being slightly different in size. 

 

A cursory measurement of my block I am currently working on has the holes as 1.631.  If I have them custom made, I can make up for rust/wear and I can get the "best" interference fit possible.  I am going to measure all seven holes in three places and come up with an average for an order.  I suspect I will end up with 100 of them...

 

James.