yes. they filled it with parafin wax @ the bottom to create an open airspace. they added the block fill, drilled vertical holes, and heated it to melt the wax back out. this creates open airspace or chambers for cooling to ensure that they don't hinder cooling around the cylinder walls. in theory... added strength, without sacrificing cooling capabilities/exessive weight gain

personally, i had never heard of it until i came across this motor. but, sinceERL did it... i imagine there was a purpose