tick tick tick

Hey guys working on a 318 that was rebuilt, with about 15 thousand miles on it so I thought I would install a 280 480 comp cam and there lifters and there springs all went well did all the right break in stuff.had no idea of the tick when I first firered it up because of the open headers.Well today I installed my exhaust kit sounds great but I have a tick at the top end booth sides pulled the valve covers off and has good oiling at the rockers,also new oil 10 w 30 any thoughts of how to find out what is happening,I dont have an oil pressure gague so no clue what its at,if I rev it its still there o I am useing the stock 318 heads for now.I guess rebuilding that 360 will happen over the winter now if we cant get this tick figured Thanks guys looks like geting her out this year is dead now:angry7: