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I could be wrong but Looking at that photo I still think it should have been a dish type of plug . In all my years in the motor trade I have never seen a cup type in core plug hole with a shoulder. It may work better than the metric dish type they are selling as imperial.[bighmmm]
1950landy - I cannot imagine a mechanic putting a sleeve in because he doesn’t have the right size plug. BUT it was certainly a cup style that came out and it had been in for a very long time. So - mystery remains but I did put back what came out and don’t think it’ll give any trouble. https://uploads.tapatalk-cdn.com/201...749af40cae.jpg
Replaced this disc plug on rear of block and 3 welch plugs on side in my '61 LWB. Has its original engine block but later head ,which has some differences from original type. Obtained steel replacements for both from Land Rover parts supplier. Note the side welch plugs are an odd size and brass ones either not available or hard to get. Apparently disc plugs were used a bit in some motors long ago. Local tractor mechanic had some in his collection but not 1.5 inch.
With motor in vehicle, is necessary to cut a hole in firewall to get at this plug. Thought best to replace it along with welch plugs, of which one was starting to leak through a rust pit. Also cleaned out rusty sludge accumulation in bottom of water jacket. Chassis number and transfer gear instructions plate had been moved down to hide where hole had been cut apparently with chisel. Firewall metal bent to gain access and then bent back again. I replaced this with a tidier larger angle grinder cut hole and made a bolt on plate to cover it. Moved the vehicle ID plate to the right of its original position.
Now important point to BEWARE! I cleaned metal surface of block and tapped disc plug in. Recall originally with a socket of size slightly under 1.5 inch OD with long extension that was tapped with happen. Then further tapped it in middle when in place so disc should slightly flare and be tight fit. Forgotten exactly what I used as gasket gunk under it but obviously was not good enough. Later local tractor mechanic reckons he has used Loctite 680 ((strongest one I know of) and none have come out. However, my first effort proved a failure. Fortunately not resulting in cooked motor. First time it got hot enough to pressurise cooling system, disc plug blew out. Would have spat out all its water very quickly but short trip around farm finished both before this was noticed and motor got hot. Then ordered another disc plug (and of course found the displaced original later) After the fright of nearly cooked motor, I drilled small holes in block each side of disc plug hole and tapped them with quarter inch UNF threads. Bolts in them hold piece of metal with two holes in it that presses on disc plus so it cannot possibly come out again by itself if sealant is no strong enough.
Anyway, seems to me that these thin disc plugs are a very poor way of pugging casting holes in engine block water jackets. Good that they have rarely or never been used on more recently designed engines so some mechanics nowadays have not come across them
The holes are where the 'core', for forming the water passageways in the casting, was held in place. With modern casting methods there is no need to have these holes any longer.Quote:
Originally Posted by mox
The discs (Welch plugs) work perfectly and last many, many years as long as a corrosion inhibitor is used in the coolant. In all my years of motoring I've never had a problem with one or replaced one (of course one will probably start leaking as I type this now !).
Mass production means they needed a low cost way of plugging the holes. The holes were originally tapped and a plug screwed in until the Welch plug was invented by the M.D. Hubbard Spring Company http://www.britishcarweek.org/welch_plug.html
I'm not sure when the parallel ones came about.
Americans call them 'freeze plugs'. If you don't run anti-freeze and the water in the block freezes the plugs push out because as ice forms the volume it takes up expands. They were not designed as 'freeze' plugs but are leftover from having to hold the core in place when casting but some people claim they were a 'safety' measure to stop the block cracking if the water froze !
As you mentioned, a 'modern' mechanic wouldn't have seen one before.
Colin