so today i was going to put in a adjustable cam gear and timing belt on i made sure the up mark on the cam gear was right and the marks on the oil pump and where the belt goes around, the problem is i can turn the crank over manually and itll spin freely but when the spark plugs are in it'll only turn for a second then stop and i dont want to force it if its jammed a valve or something.. Ive taken it off and redid it a couple times... Im not to sure bout timing never had to deal with it.. what could be the problem? thanks in advane

 

The crank should be a lot harder to turn manually with the plugs in. This is because the plugs block air from coming out the cylinders.

Check that timing between camshaft and crankshaft carefully. Unless one is careful, it is very common to be off a tooth.

If it turns fine without the plugs in; if you have set the TB tension properly; if you followed an official shop manual to do the TB change; then you should be fine.