Looking to find out if it's OK to plug the rear pipe on the left side of the block's water jacket. I'm using the engine in an MG, and don't need heat (at least for now). I'm not sure how critical this pipe is for water circulation in the block. The pipe's already out, and it looks like I can tap the block for a plug, or use a freeze plug. Just don't want an issue later, where #3 and #4 cylinders don't get enough coolant.

Mate,
are ya sure thats a water pipe? Do you mean the left side of the block as you are sitting in the car? If so, that is an air port for crankcase ventilation.

My 2 cents worth

Indeed, it is on the left rear side of the block. The few and far between pictures I've seen show a pipe inserted, so I assumed (yeah, I know what that means and does) it to be a water pipe. A quick peek will reveal if it's open into the water jacket, but it sure seemed to... At any rate, it's an issue for the morning.
The port on the rear of the head is a water port for the heater, correct? If so, I'm pretty comfortable blanking that until I install a heater of sorts.
Thanks for the insight.

Just got a better diagram and pic. It's looking like a PCV valve port. Much better than what I thought to be a water jacket gateway, and I'll be sure to put it into operation. A "vapor vent" search did the job for me.
Thanks again

Yeah I think your rear heater port comes out of the back of the head. I am putting my a14 into an mg too, but mine will be without a heater so I am thinking of connecting the two header ports up just to get some heat out of the back of the head and help in circulation.

Quote:
The hot water supply for the heater comes from the back of the head, but temperature regulation at the heater is done by controling the amount of water that flows through the heater core.

In summer, the heater is normally turned to the 'no heat' position which closes off the water supply completely. This means that during the hotest part of the year, there is no coolant drawn from the back of the head, yet the engine sufferes no ill effect.
Just plug this hole & don't wory about additional plumbing that will have no beneficial effect whatsoever.

The hole at the back of the block is indeed the direct link to the crankcase for the removal of nasty crankcase vapours & the means of preventing crankcase pressure build up.
It will be a wise man who retains the PCV function, even if it means a little custom plumbing to clear the firewall or other obstructions.