Thread size of plug in back of 2 1/4 head

[Homestar]

As per the thread title, what is the thread size of the big plug in the back of a 1960 series II 2 1/4 petrol head? It's around an inch and a half, but an exact size and thread pitch would be handy.

Cheers - Gav.

[JDNSW]

Pretty certain it is an unthreaded Welch plug if you mean the one at the back, not the one on top at the back for the heater, which is 1/2"BSP.

John

[Homestar]

Definitely a threaded plug in this head - the old one was rusted through and was replaced with an aluminium plug that was bought specifically for the job while the engine was out, but it doesn't say what size it is. The aluminium plug was a PITA to tighten as it just had a thin slot in it - and it still leaks. Engine is back in the car now, but it isn't too hard to get to. I was going to remove the Ali plug and screw in a steel one with a decent 1/2" drive recess in it.

[Homestar]

Ok, a bit more googling has revealed a different supplier that says its 1" - but not what thread it is. As it looks physically a lot larger than 1", I'm guessing BSP?

That thin slot didn't lend itself to being tightened up more than a few turns, which is probably why it's still leaking.

Welch Plug Suits Land Rover Series 2 2a 3 2.25L Petrol & Diesel

[JDNSW]

One of the plugs in this engine is a weird thread (British cycle or something?), intended for a block heater, but I thought it was in the block, not the head.

John

[50LRO]

Hi.

The ally bung on the side of the block is 1" NPT. Not sure if its the same?
I took a new ally bung to a bolt shop, they measured it as 1" NPT.
A new thread tap was close to $200. So I found one one eBay for much less.
I also assembled mine with " stag" it's a plumbers joining compound that handles heat.

Taz

[Homestar]

Thanks - I hve a tube of Stag compound so I'll use that. I'll run down to the local hose joint and see if I can get a 1" NPT steel plug with a recessed 1/2" drive or something in it.

Cheers,

[scottvdw]

I went back through my Ebay history because I bought a tap when I rebuilt my 2.25 head. The tap I have is a 1" x 16 TPI however I think this is for the plugs in the top of the head (Under the rocker cover).
I think I remember using a thread file to clean up the plug hole in the back of the head but I don't recall the pitch.
I used an aluminium plug from roverparts plus item no R230250 "WELSH PLUG (BACK OF CYLINDER HEAD) - L/ROV (1 3/8") (1.375") screw in (1 req.)" but it had no drive at all (no slot or anything...) - I cut a slot in the back and wound it in with a lot of stag. I also peined the edge of the plug to expand it slightly into the hole after it was fitted.

Scott.

[schuy1]

X2 about the "stag"jointing compound. Just be aware it does harden over time so can make stuff hard to get out, other than than that there aint many modern compounds that are better With the alloy bungs in the head and the side of the block water jacket I use a reamer to take them out to 1" and fit brass drive in welch plugs, problem solved
I have seen the alloy threaded plug in the rear of a '60 2 1/4 motor but not on a '62 model and later.
Cheers Scott

[mick88]

Service removeable Loctite (Blue 242 or 243) will seal it and won't be likely to deteriorate over time.


Cheers, Mick.