I was out enjoying the fall weather last week in my '67 327 conv't. All of a sudden it lost power and started running rough and backfiring. I got it home OK but can't figure this one out. It's hard to start and when it is idling it backfires out the exaust in a rythmic cycle. Almost like counting "one, two, three, backfire, one , two rthree, backfire". Also lokks wet on the floof by the exaust (raw fuel, water?). I took off the valve covers and it looks OK I also checked the timing (8 deg. BTDC)I changed the plugs and wires(They all looked good. tan and dry. What next? Head gasket? Cam?