my friend is having a problem with spark. it's really weird because cylinder 2 and 3 have spark but 1 and 4 dont. does anyone know what could be the problem?

timing and the distrubutor are fine....

 

Sometimes the contacts inside the distributor in your case 1 and 4 don't pick up the correct current when the rotor arm passes them, if you give the contacts a good clean up this can rectify the fault once you clip the cap back on.

 

x2 for replacing dizzy cap.