valves??

so i got my engine together i go through the steps of timming it i make sure im at tdc, and my cam is in up position, my dizzy is fireing on the first cylinder i get the car started did not sound good. a few friends say "my pistons hit the valves if i had a really off timming on it"...any info on this one????thanks

mnaually put you car back to tdc and see if the marks line up

Your friends are right to an extent...if your timing was off a lot then the exhaust valves would smack the top of the piston, but if it was off only by one cog on the top timing gear then it will just run like crap. When you put the timing chain on the two gears, did you make sure that the slack was out of the chain and that all of the timing marks lined up??