Weeping Core Plugs

[ian_h]

Hi
I have a couple of weeping core plugs on by 100M
Have changed a couple of times over the years (new core plug put i place and hit in centre with round headed hammer) but they don't seem to seal properly.
Does anyone have a better method or magic sealant I could try?

I believe you can also get rubber plugs which tighten with a screw. Does anyone have experience of these?

Many thanks
Ian

 

[Randy Forbes]

Historically, you'd smear some Permatex around the perimeter & put them in. Nowadays, I use Loctite 518.

 

[Michael Oritt]

Ian--

I would not recommend using the rubber plugs and I regard them as temporary fixes. Dorman and others make a two-piece all-metal plug which tightens via a nut on a stud that expands the cup. Simply for esthetic reasons I would not use them on my Healey but do on the MGA race engine of my Elva Courier and bed it in JB Weld after carefully cleaning the shoulder, etc. of the hole. I have never had one come out.

 

[CraigC]

Hi
(new core plug put i place and hit in centre with round headed hammer)

This right here is your problem. I don't care how many different places you have read it or heard it, it is WRONG!
I was shown the correct way 40+ years ago by the machinist who prepped my 100 block during a rebuild. The dish-type plugs seal and hold in place by generating outward pressure while being nearly flattened. The proper tool will leave a slightly concave center in spite of the tool being essentially flat. This is probably where the incorrect method came from.
Go to this page https://www.hubbardspring.com/product/expansion-plugs-brass/ and then click on "installation instructions". There you will find the image below.


You will see that the tool is flat with a slightly dropped center. This will create considerably more outward pressure to secure the plug. My 100 is good testimony to that. Never lost a core plug and never had weeping from the perimeter. Old age and corrosion did them in. They were replaced last year with brass. If they ever need replacing again it wont be by me. I dont expect to be around another 42 years.

As a distant second to the correct tool, one could use a socket of nearly the diameter of the plug. Turn it around so the back of socket faces the plug. Using a (sacrificial) extension(make sure it does not protrude past the back of socket) strike the plug until it is close to flat around the perimeter. No need to get carried away, you don't want to break the block!

As always, a little sealer in the block cavity for good measure. I always used the Permatex red liquid sealant on core plugs, both to seal the perimeter and coat the surface exposed to coolant.

 

[Randy Forbes]

+1, as evidenced by the UHMW "tool" I have in my hand, along with the sealant and core plug. I like the way it dampens the blow__and leaves no tool marks whatsoever.

 

[ian_h]

Excellent many thanks for the insights
what is the best way to remove the old plugs?
i guess you could drill small hole in centre and insert self tapping screw and then lever out but not keen to get swarf in the block?
ian

 

[Randy Forbes]

They're usually weakened from the backsides corroding, so you can drive a screwdriver into them and lever 'em out. I'm typically sending the block/head to be hot-tanked anyway, so I don't worry about a little bit of shavings in the water-jackets (if you've seen some of the things I've pulled out of them, you'd know the manufacturer desn't worry about it either...).