Toyota Repair: 2000 rav4, engine noises, timing belt

Question
i went on vacation for 4 days and when i came back and started my rav it made a hell of a noise coming from the engine that lasted for about a minute and then went away and car seemed to run fine after that .i have had a new block and vales installed 3k ago. and everything seemed fine until this .i am wondering if the oil septed out of the head from sitting so long or if i screwed up and and should of had the O-rings done too.
thanks for any advise  

Answer
Even after sitting for four days there should be no noise from the engine, from your description I can't tell what the problem may be, I need a more specific description of the noise, ie: knocking, grinding, clicking, etc.
It's possible that there may be a problem with the timing belt or the water pump, these are the most common failures that cause engine noises on this model.