Cylinder head core plug?

[vxah]

Can anyone enlighten me as to why a few twink cylinder heads don’t have a core plug on the mating surface at the breather box? There is a head for sale on eBay without it and it got me wondering as mine does not have one either!
I thought it might have been welded up at sometime but that does seem unlikely?

[rgh0]

I would need to do a bit more checking of some of my spare heads that have the core plug but I think Lotus changed the inside design of the oil disengaging chamber at some stage to not need the core plug for removal of the casting sand.

cheers
Rohan

[vxah]

Are these the correct numbers?

Hi Rohan, here is my head in case the numbers mean anything?

[rgh0]

ED004EF6-B61D-4D4E-BC5B-41B5738F62D4.png

Hi Rohan, here is my head in case the numbers mean anything?

Not sure what those numbers that appear on the bottom face of many of the heads relate to - probably some sort of batch numbering during the casting (the cast in ones done with dymo tape) and during the machining ( the stamped in ones).

I have had a close look at all my heads and only one, a late Weber head does not have the welch plug in the oil drain chamber. Looking closely I can see a faint indication when the light is at the right angle of where the plug would have normally been. Its not clear if this is a ghost mark left from modification of the casting pattern or where the hole has been welded up at some time. Maybe all the heads without the plug have just been welded up at sometime during maintenance, maybe Lotus changed the casting at some time or welded up the hole instead of fitting a plug during manufacture.

The 1973 Weber head from my Plus 2 has the welch plug so it does not appear to have been a systematic change during manufacture , as much as Lotus ever did anything systematically

cheers
Rohan