????? about Valve timing

Okay so I lined up my cam gear and timing belt and 1piston at tDC took off the timing belt put my skunk2 gear on put everything back on and now it wont start this fn sucks I thought I did everything right and its such a Bisnitch taking and putting the timing belt back on and off. What am I doing wrong.. The other mech in my shop said that once you take off the timing belt the piston will tend to drop on its own is this true?/ Did I take to long to put the belt back on?? What might be the problem?? My valves aren't bent or hitting so thats good when I tried to start it it just had a hollow backfire......Adn when I did a compression test so the compression was only like 75 80 normal is like 135... Are my valves no closed all the way how do I fix this problem any advice will help Im tryin to fix this myslef or else I will just have to take it to a shop and have it professionally done....

well its sounds like your timing is off so i would start from scratch with the timing just be patient double check your self , and your compression is very low you may have a serious problem with that. but first check your timing use a chiltons book.

Yeah I solved that problem by swaping a GSr into it

Did you take off your crank pulley, and set the crank at TDC. Or, did you half ass it, and leave it on, while just trying to change cam gears?