need help asap

I just finished a rebuild on my ej25d but now it has no compression in cylinder 3? i need some help on what it could possibly be. could it be in the heads? i put the piston rings in proper order with a 180 offset. i've got an ej22, will the sohc head fit on the 2.5 block? if so are there any special requirements? i really need some help to get my baby back on the roads, any help would be greatly appreciated.

How are the valves adjusted on those heads?

the only thing i did with the valves was replace the valve stem seals, but the valves appeared to have seated properly.

did you put the ''buckets and shims '' back where they came from. the buckets are interchangeable when factory new (not sure about them after 100k miles of wear), but the shims are specific to each valve and determine valve clearance.

if you did all that right, you used the wrong timing marks when you installed the belt.
what alignment marks did you use?
NOT the ARROWS, NEVER the ARROWS.

those are the two most likely causes.
even if the valve shims are not perfect, if you put them back where they came from the engine should start. so if you paid attention to that, the timing is off.

being mistimed, is the number one cause of a no start situation after major engine work.

i think i know what i did wrong. apparently there's 1 offset piston and i didn't realize it because they all looked the same diameter and side skirt length, but i just so happened to run into a subaru tech and was talking to him and he said that was likely the cause of not having compression at all in one cylinder.

the car still started up though, it was just running off of 3 cylinders.

and i didn't memorize the location of the shims, i had them in order but my friend rearranged them. 0.o