Engine Block Drain Tap Made not to Work!

[svenedin]

I have been having a tidy up of my garage. I managed to give away 2x 1098cc engine blocks to a friend from my MMOC branch. They have been in the way in the garage for 35 years! Suddenly I have the floor space for a small workbench but I digress...

I found a brass block drain tap that I never got round to fitting. In the packet the instructions state that if you want the tap to actually work, you must remove a threaded insert. Basically, it is for show unless the end user takes the time to lap it by hand (see instructions).

I wonder if this is a very unusual cause of drain taps not working as intended? It does not apply to the originals, only to later replicas.

So how would one go about lapping this drain tap to make it work as intended? Brasso or Autosol in the taper and patiently work the tap round and round (having of course taken the split pin and spring off)?

Stephen

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[geoberni]

Stephen
This appears to be the same drain tap that ESM list, though currently showing as Out Of Stock....
https://www.morrisminorspares.com/engin ... ck-p830297



At £25, I'm not sure I fully accept the statement on that leaflet about cost effectiveness to justify it leaking....

[svenedin]

Yes that looks the same. I just found it rather absurd to have a tap fitted that is purely for ornament and blocked on purpose!!

In fact, the later engines just had a drain plug rather than a tap. Presumably this was done for cost reasons or perhaps also problems with the taps leaking. Ironically, it is even more useful to have an engine block drain tap with a later engine than it is with an earlier engine. This is because the later engines have a silly design of the heater return pipe going over the top of the thermostat housing and being secured on 2x cylinder head studs. To access the thermostat (some people like to have a Summer and Winter thermostat of different temperature ratings) 2x cylinder head nuts have to be removed and to be safe it is essential to drain the water below the head gasket (and to do this on a cold engine). A tap at least means that the coolant can be collected in a suitable container whereas a drain plug inevitably means coolant spills everywhere. Of course there is also a radiator drain tap so I presume the thought was that a separate engine block tap was not really necessary. The radiator drain has a very narrow bore and drains very slowly even when there is no sludge present and if there is muck in the coolant it is next to useless.

I have tested the tap by blowing down it and it seems to seal perfectly but whether it seals with hot coolant water under normal operating conditions is a different matter.

Stephen

[unclealec]

I regularly overhaul this type of tap for Riley RM series radiators. I find that fine valve grinding paste followed by a fine cut session using Solvol Autosol brings a leakproof fit.
The difficult job is getting the split pin out!

[svenedin]

I regularly overhaul this type of tap for Riley RM series radiators. I find that fine valve grinding paste followed by a fine cut session using Solvol Autosol brings a leakproof fit.
The difficult job is getting the split pin out!

Thank you very much! I will do as you suggest. Presumably that spring is quite powerful and makes getting the split pin out troublesome? I suppose it needs compressing somehow.

Stephen

[unclealec]

It's not powerful Stephen, but it is very short, so the compressionability (?) is minimal.
And it is usually encrusted with so much crud that it can well be beyond use due to rust.
In case it helps anyone, I cut through recalcitrantsplit pins with a junior hacksaw so that the brass washer and restrictor platecan be lifted off, then I remove the cone from the housing and hit it with a Mappgas torch. The remains of the split pin are easily drifted out using a fine pin punch.

[svenedin]

Ok. For the lapping do you just work the tap around by hand having put your fine valve grinding past inside?

Stephen

[unclealec]

Yes, that is how I do it, and it works most every time. Light smear of paste onto the cone, the push it into its bore and work by hand, checking every now & then. Doesn't take long with the soft brass.
You could check it with engineers blue to be sure.

[bobtail4x4]

I can see the logic, how many times has the tap been knocked half open without knowing?

[svenedin]

Yes, that is how I do it, and it works most every time. Light smear of paste onto the cone, the push it into its bore and work by hand, checking every now & then. Doesn't take long with the soft brass.
You could check it with engineers blue to be sure.

Brilliant. Something to do on a boring winter evening when the garage is too cold!

Stephen