Twin H intake casting welch plugs

WABOOM

Hi guys. Sone of the casting plugs on my Twin H are leaking. I bought some new ones. Can you tell me the best way to install these?
Also is the hole in the casting a full 7/8"? After driling to remove the first one I took out, I can tell if there is maybe another in the manifold... like maybe 2 were stacked in there. See pic. 
Thank you

cheyenne7271

Just knock them in with a socket and hammer

cheyenne7271

It is 7/8” and not very deep

WABOOM

So the 7/8 diameter goes right thru the wall of the casting? If so. someone must have doubled up one of them.

WABOOM

Nevermind. You said not very deep.

ratlee2

Just put them in the hole with the dome facing up and hammer flat using a smaller socket.  They will expand when flattened.

WABOOM

Thank you gentlemen. 

GrimGreaser

A bit more information, for those inclined: Seastrom Manufacturing (seastrom-mfg.com)