Ok kids,

When you have never done this particular job on a mini, I have a few questions.

1. Are they welsh plugs, welch plugs or core plugs???

2. There's three across the block front and one at the side - correct??? (I always thought there were 5 in a mini)

3. When putting them in, is Loctite 243 a good enough sealant.

Cheers all

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Rod
http://smg.photobucket.com/albums/v607/Rodney/

1. Welch or core plugs - same thing
2. Three plus one = four.
3. Make sure all surfaces are spotless (no paint, rust or scale) and use a sealer sparingly. 243 is a thread locker, use a non-silicon gasket cement or thread sealer. Your GMH dealer will sell you a small tin called 'Holden Sealing Compound #3835215 which works a treat on most applications like this.

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Curly
'64 Cooper 'S' (Group Nb spec)
'67 Mini Marcos GT www.mm7056.wordpress.com

1275 has 5 plugs - small bore has 4

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David L


My greatest fear in life is that when I die my wife will sell my Mini and tools for the price I told her I paid for them!

Wot they all said but there is more.

To get the old ones out you get a medium drift and a hammer and simply place the drift at about 3.00 and tap it with a hammer. The plug should start to turn in the plug hole. Grab it with a pair of multi grips and pull it out.

Pay particular attention to cleaniless around the plug hole. Make it real clean.

You will find the flat surface of the new plug has a convex shape - note that.

Push and very lightly tap the plug into position in the plug hole until the outer ring edge is flush with the block.

Then get the drift you used to remove the old plug. Put the drift dead centre on the convex part of the flat surface and give it a sharp tap with a hammer - it should go slightly concave. This spreads the load across the plug hole and locks the plug in place.

Loctites and the like are a good idea but they wern't available when these engines were being built. It was done as i just described.

Mike

Maybe the A+ 1275 engines had 5 (2 smaller ones on the side I think), but I'm pretty sure that my Cooper S engines only have 4.

There's also a different design of plug between the small blocks and big block. The small blocks have discs, the big blocks are cup-shaped. Mike's advice is spot on, they never used sealers originally, but back then the holes hadn't been in service for 40 years .

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Curly
'64 Cooper 'S' (Group Nb spec)
'67 Mini Marcos GT www.mm7056.wordpress.com

Stag is a good sealant i find.

Matt

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And they can pop out at the worse possible time......

One way to stop the silly flat ones from blowing out is to fit retaining screws to keep them in.
You drill and tap a small hole into the block on each side of the plug and use a screw and washer overlapping the plug to keep it in. You can even fit a strap across the plug for more strength .

1100S etc and later 1275 ones have 5, the S had 4.

The cup ones are easier to fit, I select a socket that just fits inside the rim and tap them in with BFH.
As said clean the opening out well, and Stag is the best sealer ever invented.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Isn't the (partial) idea of them to give somewhere for excess pressure to escape by popping the plug instead of cracking the head in extreme conditions or is that just a myth ?

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I have heard that in the event that the water or coolant were to freeze the welsh plugs are the weakest point so these are forced out thus preventing damage to the head block etc etc. Not sure how true this is though. Can anyone verify this?

Matt

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I know they are a by product of the casting process as well but I've heard them explained like that . Anyone ???

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The real reason for these holes was to get the sand out after casting.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Yeah but wasn't there an ulterior motive to using a pressed in plug rather than something more substantial or was the "prevent cracking" an excuse to cover using a cheaper pressed in plug instead of a more expensive threaded pulg or something . I'm talking engines in general , not just mini ones .

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The Yanks call them freeze plugs because if you freeze the water in the block, the expansion pushed the plugs out. Dunno if it saves the block from cracking though.
I remember Mitsubishi had some problems with the early Astron blocks cracking near the welch plugs, but it was a design fault.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.