timing marks

hey i know this has probobly been covered a million times but i have my bottom sprocket mark lined up properly and i have the one and arrow at the mark up top on my cam and i dropped my distributor in and its pointing at number one and it cranks and runs fine. when i put a timing light on it the mark is pointing up straight up like with the mark on the bottom sprocket when i put the belt on instead of over on the timing guide on the timing cover. whats up with that


thanks in advance
justin
ps i love this site so far im really learning alot

U apparently have ur truck timed at 0 degrees Top Dead Center (TDC).Factory specs call for 6 degrees before TDC (where the mark is on the cover).U can leave it there I guess except u will notice some ping and valve rattle unless u run high test.BJ

but when i put it to where the mark is on the cover it wont run. this is the only place it will run and run good, the truck is .40 over with a weber and header, and full exaust would this change anything

Then if that is where it runs best I would say leave it there.Ihave a Weber ,cam ,stiffer springs and al retainers,aluminum underdrive pulley,Accel and my truck is at 5 degrees BTDC and runs great there.Maybe where u r timed is where u need to be.BJ