Your crank pulley is about to come apart.When it does,the engine jumps time,and the valves will hit the pistons.I would not suggest driving it any further,as if it lets go,it can ruin the engine.
The fix is removing the crank,and having it machined to accept a newer style gear which will not slip.
Do a search on this site,there is a TON of info on this subject.
There is also an updated balancer and alternator pulley to help take the load off the gear as well.