Spark plug leaks

[pan620]

I have two different knucks around the shop and while pressure testing one of the manifolds for leaks I found the rear spark plug leaked bad around the seat area, swap a new plug in with the same outcome, tried the other engine with same results. Front ones on both engines seem fine, any thoughts? Thanks Dave

[1950Panhead]

Are you using D16 ?
There is a seal ring on the plug.
The seal ring is shot or you have a head defect, check both.

[T. Cotten]

Dave!

I cut oversize seal washers from PEEK when they can cover the blemish or crack. And of course, I cut different thicknesses for indexing as well.

....Cotten

[pan620]

Yes I have been using D-16 plugs but tried other brands,(New) with same results.I do not see a crack or blemish in either head but i dont see as good as I use to. Tom I will be in touch with you soon, Thanks

[pan620]

I tried one of the Peek seals I got from Cotten on one of the heads and all is well, no leaks! Hopefully with a little more time I will have it running like new.