View single post by Esprit2
 Posted: 07-21-2020 03:40 pm
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Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 547
Those plugs are for oil passages, NOT coolant. See the attached illustration. The plugs are known to develop leaks, but oil, not coolant.

They were plugged with 1/8 BSP (or BSPT ?), Allen drive grub screws (plugs). The threads were originally sealed with automotive grade silicone sealant (RTV), like the Permatex Ultra series.

I'm not a fan of using silicone sealants in engines, especially in part of the oil system. But given that it would be a challenge to get all the old silicone residue out of the threads, it's probably best to stay with silicone.

Note that the cam shafts are 'gun drilled' full length to deliver oil to the bearings. At the front of the cam, a grub screw is first screwed in full depth and seated. It's threads are sealed with a little silicone sealant, and a little more is smeared over the top. Then when the bolt that secures the cam pulley is installed, it's threads, and the threads in the bore are also smeared with silicone sealant (use a Q-tip/ cotton swab).

Tim Engel

Attachment: 9XX Cyl Head - Oil Passage Drillings for Cam Bearing Lubrication - 95kb.jpg (Downloaded 128 times)

Last edited on 12-01-2020 02:20 am by Esprit2