Half moon cam plugs

[Tim]

I had a 'moment' at the weekend with smoke pouring out from under the bonnet, but it was just one of the half moon cam plugs having come out at the rear of the engine on the exhaust side so oil was splashing out and burning off on the hot exhaust. I found the missing plug in the drip tray in the garage and decided to replace the lot. I ordered a new set along with, new selocs, nylocs, cam cover gasket, avaiation gasket No 3, Loctite high temp sealant (as Rohan advises) and will take the opportunity to check and torque the head bolts. So far so good.

The new half moons arrived today. They look great and have the same "BJS" logo as the one that fell out, but they look much smaller (see the attached photo). Both thinner in section and radius. Before I try to fit them and get into a mess (I am a terrible mechanic and usually make everything worse when I try to fix it) does this sound right? Do they swell in the heat when installed, absorbing oil from the cam cover, or does anyone think the new half moons look wrong?

[billwill]

They look OK to me. Perhaps your old ones had swollen a bit from absorbing oil or heat.


You need to put them in with sealant of course, but the top surface is covered by the cork cam-cover gasket, so it should still seal well with a dab of sealant.

[checkrail]

I have found sometimes that they are too deep for the cover to compress so trim with a scalple and steel rule
Watch the fingers!

John

[cadwell]

I have bought some Triumph Stag half moons which seem to be much better, they have side shoulders which locate the seal and are the correct size. Has anyone actually used them on their car? Mine is still in rebuild.

Peter

[fatboyoz]

Hi Peter,
Have just removed the lip type half moons. I was told that they didn’t require sealant, but they seeped enough oil to run down the face of the front cover.
I am awaiting, hopefully today, some aluminium half moons from Lotus Marques in Melbourne. I have had them fitted in the rear of the head for many years with no leaks. I am going to fit them to the front as well, fitted with sealant, they also sit flush with the surface of the top of the head.
If fitted with sealant, I think the lip type half moons would be fine.
Cheers,
Colin.








quote="cadwell"]I have bought some Triumph Stag half moons which seem to be much better, they have side shoulders which locate the seal and are the correct size. Has anyone actually used them on their car? Mine is still in rebuild.

Peter[/quote]

[rgh0]

Generally I find the half moons shrink over time rather than swell but i guess either could happen depending on the rubber compound actually used. A new half moon should be a tight fit in the cut out half circle and sit flush with the head outer face and top face. if your new half moons are at all loose I would look to get a set elsewhere.

cheers
Rohan

[promotor]

As mentioned earlier the Triumph Stag & TR7 plugs fit, although a little bit of trimming is needed for the ones at the back of the head as they get bent out of shape.
The ones in the photo are nice and soft - compared to proper Lotus ones which seem to be almost made of plastic.
They do give slightly different look to the head though!

[rgh0]

Look like a nice alternative to the standard plugs. i musty order a set to compare

cheers
Rohan

[promotor]

Look like a nice alternative to the standard plugs. i musty order a set to compare

cheers
Rohan

The Stag and TR7 engine use exactly the same size line bore for the cam so these fit nicely in the cam tunnels.

The design should at least stop them blowing / falling out!

[2cams70]

Lotus Marques supply these as well. I fitted the Lotus Marques aluminium ones at the rear and this type with a lip at the front. Aluminum at the rear because they will never leak and are never removed during regular servicing. Rubber at the front (no sealant) because they may need to be removed during valve shim adjustment. Use Threebond 1217H on the aluminium plugs. You definitely need a good quality adhesive sealant to stick them in. The aluminum plugs don’t have the lower location “pip” the original rubber ones have. If the sealant fails there is a possibility of the plug falling either out or into the engine.

[gjz30075]

Volkswagon Rabbit / Golf uses the half moon with the lip, also. I have those fitted. In fact here's a good
buy:
https://www.ebay.com/itm/252927172162?e ... R_j70bSwYg

[phil1800]

Greg,

can you give more details about the VW Rabbit engine? Which one and what model year?

Thank you!!

Philipp

[gjz30075]

Phillip, I think they are for any Rabbit from the late '70s to early 80s. I don't recall having to be
specific (when I bought them from the VW dealer). I think many water cooled VWs with an overhead
cam used these plugs. Here's a good buy:

https://www.ebay.com/itm/252927172162?e ... R_j70bSwYg

[phil1800]

Greg,

thank you! Plenty available in OEM quality ( neoprene- silicon ) from Elring Klinger for @ €3 per piece.
VW part 049 103 491
I will report, once I have received them.

Philipp