Problem with SOHC

hey im not looking for any trouble im just genuinely in the dark on this. the problem is as goes:

replaced old ka24e with a model rebuilt by Attarco (sp?) out here near sacramento, for those of you who know it. it primarily deals with jdm engines and so forth, i know. but i bought the engine from an individual who stated that the engine cranked but would not turn over. i promptly jumped on the deal and bought the rebuilt sohc and tranny for 250. my buddy just installed both and now we are realizing the same problem. to prevent the simple questions: it has all fluids, new oil filter. i am heartbroken because i love my little 240. so if you could toss a couple hypothesis my way as to why the engine will not turn over, thatd be awsome. there was an individual that said it sounded like there was no compression. again, im not looking for ridicule because i already know i dont know much about cars. PLEEEEASE HEEEEELP.

engine will not turn over as-in ,when you turn the key to the start position it will not crank, or the motor cranks but will not start?

spark, fuel, compression, timing. check it all, in every step.