Lost Frost plugs
An electric run in stand does not break in an engine. It is useful for verifying oil pressure and checking compression on all cylinders--that's about it. Good news though as I would bet Dollars to Donuts that there were never any plugs in the offending holes. Don't use sealant--use Permatex/Loctite Green Sleeve retainer--It works the best--forever and ever. J.Rob