have a 1969 5 ton in shop with blown head gasket.guy that owns truck brought in with head gasket blown in front. we had heads shaved and tested,popped the gasket in back.i don't have a clue how multifuel works.could this be the pump out of time or the manifold,or blower. this is a Lds-465-1A engine may be someone has had this problem before.I'm stumped thanks