Core Plug Sealer (1 Viewer)

[Stevepipeman]

The machine shop has no experience with the shallow core plugs for my 71 "F" block. What's the preferred sealer of choice of experienced Land Cruiser builders? Thanks

 

[thebigredrocker]

The core plugs are supposed to be dented. They are Welch plugs, which are installed into the stepped hole in the block and then whacked in the center to spread the plug a few thousandths, locking it into the hole.

Ideally, a Welch plug should be flattened for maximum expansion. If there is a dent in the center but much of the disc is still convex, then there is wasted expansion still in the disc. The hole and the lip the plug registers against should be clean & smooth. Seal the outer edge with Permatex#1 or equivalent. If the plug won't fall into the hole easily, then use a large OD socket or pipe to drive the outer edge in until it registers on the lip. Then turn the socket around and use the flat top to flatten the plug.

 

[thebigredrocker]

This is incorrect in 2 ways.

First, a Welch plug is a very specific type of convex round plug w/ a sharp edge. It is installed in a hole w/ a stepped bore. The plug has to be beaten flat once installed to expand it for the proper seal/press fit.

Second, 'freeze plug' is hillbilly slang for a core plug. Core plugs are used to plug core out holes in complex castings (engine blocks, heads, manifolds...) that are used to clean out the casting core material (usu. sand). Core holes are usually finished to a smooth bore and sealed w/a press fit cup plug. Vintage engines may use a welch plug for this purpose, but manufacturers got away from them ASAP, because of the more expensive machining and installation cost. Aviation and racing engines may use threaded core plugs.

The proper sealant for either a welch or cup plug is Permatex #1, hard setting. Silicon RTV sealers are actually slippery which is good for gasket expansion, but bad for mechanically retaining a plug.

A cruiser tip for the rear oil & cam plugs: If there is a concern that the plugs might leak or pop loose in use, fill the outside of the plug w/ JB weld, put a piece of clear packing tape over the plugs, then immediately bolt on the BH. After goop has hardened, remove BH, peel off tape, proceed w/ engine assembly as normal. Solid goop will insure that internal oil pressure cannot blow plug out to back of bore and really gush oil.

That's all I got.

Happy holidays or bah humbug, your choice.

 

[3_puppies]

The machine shop has no experience with the shallow core plugs for my 71 "F" block. What's the preferred sealer of choice of experienced Land Cruiser builders? Thanks

go to a different shop.

 

[Stevepipeman]

Thanks for the great info. and your consideration.

 

[FJ40Jim]

You're welcome.