4 replies to this topic

[whistler]

Friend of mine had a head gasket water blow and when we removed the head we found that 1 of the 3 small core plugs in the head face had perforated. We fitted a new head gasket but I'm concerned that we couldn't swap out the rotten core plug. Anyone know the part number for these little beggers. It seems to be the 12G940B head that has these not the standard 12G940.

[nicklouse]

are you on about the brass plugs in the head? they are not all present and they are not all the same size.

 

pictures of your perceived problem.

[Spider]

Some heads had solid plugs and the later ones use a miniature freeze style plug and I'd guess here that your friend has the latter.

 

When these type need replacing as there is a shoulder in the head, I turn up solid brass plugs and fit them proud with sealant, then a light skim of the deck. This way, you can be sure they won't move, which was an issue in the earlier heads and can be in these if there's room for them to move.

 

In the earlier heads that don't have the shoulder, I have threaded cast iron plugs that I fit and again, skim the head deck. Brass plugs in these heads is asking for trouble, I'd say around 50- 60% of these I've come across have shifted and caused problems.

[whistler]

They're like a miniature versions of the block core plugs, being made of steel and like the top of a rattle can. I have a spare 1992 carb 12G940B head and that has the same.
I've attached a picture of my spare head, showing the 3 plugs circled.
The top left one is the one that has about a 3mm hole in it.
I'm hoping that there is a part number for these as that would be the ideal fix, just to replace it.

Attached Files

•  DSC_00201.JPG   81.65K   2 downloads

[whistler]

Just had a reply from Tony at bullmotifminispares and he thinks that 12G3503 is the one. Also used as oil way plugs.They're the correct size and look correct. Thanks Tony.

http://bullmotifmini...up_1980_onwards