Amazon: Core Plugs

[Bracpan]

I am rebuilding a cylinder head with hardened valve seats and new valves and guides etc im going to replace the 3 core plugs in the head.
I don't want to risk them leaking so what would be recommended as a good sealer to use when I refit them ?

[142 Guy]

The most important part is to make sure that opening in the casting that receives the plug is absolutely clean and free of any burrs. For the large domed plugs used on the B20 block and head, I placed a small ball peen hammer with the flat side of the head applied on the high point of the domed plug and then applied a firm tap to the back of the ball peen hammer with a 2 or 3 lb mallet. The general guidance is that the contact implement' should be about 1/2 the diameter (or a little less) of the plug. Too small and the deformation of the plug at the contact point will be too high. I used a brass drift on the smaller plugs.

I never used any sealant on mine and it has been fine for 10 years. If you feel better using some sealant you can find competing sources which recommend both anerobic flange sealants and RTV like sealants. Permatex 51531 / 51550 is an anerobic sealant for very thin gaps (0.015"). Anerobic flange sealants tend to be thin bodied and the Permatex requires a cleaner / surface activator. Permatex Ultra is an RTV like 'gasket maker'. If you think you have some significant deformations (> 0.015") in the sealing surface of the casting hole then I would be inclined to go with the Ultra or some similar gasket maker like product. Just don't go overboard with the RTV because you don't want to squeeze excess into the casting hole and have chunks of RTV floating around in the cooling system.

[Volvo_133]

Its been a long time since I replaced a core plug. As mentioned ensure the casting is clean and fit core plugs dry.
An old trick I was taught was to fill the cooling system initially with water only. Use the car for 1 week, which will allow a harmless small amount of rust to form. After 1 week drain the system and replace with antifreeze mix.
For obvious reasons this is a May to September job in the uk.

[blueosprey90]

Prior advice is excellent, but ....

Not Volvo, but if you want something trick. take a look here.

https://www.mgexp.com/forum/mgb-and-...21425.4621613/

See post #3. I have the core plug strap retainers shown in the first 3 photos of post #3 on my MGA Ghost Main engine.

I have the Hemi style core plug shown in photo 4 of post #3 on my MGB 3 main engine - and those are really sweet. Scroll through the two links in post #3 for some ideas on how they might be fabricated.

I have the Dorman style acorn plugs on my MGA 1622 engine - Google Dorman 02483 to see what that looks like.

Also see post #6 in that thread if you go with the stock type core plugs.


With all that said, I don't have a clue what I have on my Volvo B16B engine.

[Derek UK]

If the seat for the plug is corroded and rough, clean up as much as possible and use a bead of marine JB Weld around the seat before before seating the plug with ball pein or small socket. Suggestion only.