Cylinder Head Venting

[Muddy]

G’day from Australia Aficionados

I have finally gotten around to starting the engine reassembly of a 1964 C72 Dream that I purchased several years ago.

The engine had sat around in previous owners’ sheds for long periods of time and was rather neglected when I picked it up.

Mud wasps have got into a lot of the crevices and holes. Two of the worst affected holes are those in the vents of the cylinder head either side of the intake manifold. These are the small vent holes that usually have the barbed fitting screwed into.

I have cleaned out the mud wasp nests and found lots of what appears to be aluminium corrosion in the holes. I’ve cleaned this out with a drill bit to a depth of about 50 mm (2 inches) and hit what I think if the head casting. I cannot blow compressed air thru the vents and can’t determine where the holes lead to within the head.

I’m very interested to know what the purposes of these vents are, where they go to in the head and if they are necessary. Does anyone have some knowledge they can share please?

I’m also interested if anyone has just chosen to blank these holes off – they appear to be an M8 x 1.25 mm thread.

Thanks.

Regards

Muddy

[Tim Allman]

Originally they were connected to the air filters. (The filters had suitable nipples but apparently the connection is unnecessary as the later air filters had no nipples.) Here's a video with an explanation which seems plausible.

https://youtu.be/Vce9k1nsQx8