cylinder head help

[hrdrsrman]

just removed plugs from a 1959 johnson 35 hp seahorse. lower cylinder plug was removed and seemed as if a sleeve came out with the plug. question is.....was this a factory sleeve or was this done following a rebuild? Not sure about this engine history as it came w/a 1958 cruiser inc. found in a barn.

 

[ibnfshn]

Sounds like someone stripped the threads and put a helicoil in it.

 

[hrdrsrman]

Sounds like someone stripped the threads and put a helicoil in it.

Doesn't appear to be a typical helicoil as it is a threaded sleeve both inside and out. I need to research this engine more as it appears the top cylinder has a similar sleeve that remained intact when removing the plugs. Thanks for the reply.