Recently bought used .61 super tigre engine and downloaded manual from internet. Ran it for first time yesterday. Looking at manual this morning noticed there should be a gasket between exhaust manifold and engine but there is none. Question is is it necessary and if it is could I use liquid gasket in a tube or should I find some kind of material to make one. Also very hard to tighten muufler to engine, screws want to come loose should I use lock washers or lock-tite(used lock-tite once on engine and almost could'nt get screws off again.)