I trust that this post finds you all healthy!
I am taking the Covid19-isolation opportunity to give my 3.5 litre MkIV some overdue maintenance, including a head job, water pump and radiator clean out. I removed my water pump with a view to replacing it with a refurbished one (thanks to Mike Wilding). Removing the cork gasket revealed another hole in the block next to the inlet hole from the pump.
The parts book only shows the reverse engine view so no clues as to why an engine would be built with a hole which is only sealed with the water pump plate gasket - or should it have had a welch plug?.
Can anyone enlighten me?
Here is my 3-1/2 L Mark V.
The water pump has an aluminum spacer casting so is different from yours but it seems to be just a blocked off port.
Looking at it more closely, it is indeed a core hole, in that it is a remainder from where the sand core had lugs which sat in pockets in the sand mold when the molten iron was poured in. The sand core forms the shape of the water jacket inside the block. It is broken apart and shaken out as loose sand when the block is shot blasted after it is shaken out of the mold. Unlike the other core holes, this one needs no Welch plug because it is up against the water pump parts.
To add to Rob’s remarks, when the block is not used as a coffee table, the water jacket does need to be sealed at that hole, but the sealing does not require a welch plug when sealed by a plate. Just make sure the sealing plate does not have corrosion preventing sealing when everything is cleaned up. On the Mark V the C.2810 Cover for Water Pump can corrode, so just use some awareness on making it seal well when put back together. The water pressure in the water jacket is close to atmospheric so sealing is not difficult, a plate can do.
When you’ve finished that one I have two other 3 1/2 Mk IV’s available for purchase.
One of which was recently in roadworthy condition in SA.
Let me know if you have any mates there looking for one.