hauffmanstuppe

Hello, I recently had some issues with my daily driver 94 Civic CX (threw a rod) and purchased a used engine from a parts yard. Original engine is a D15 b6 and replacement D15 b7 non v-tech engines. My question is that after putting in the used engine things just don't sound right when cranking. the engine isn't running, I have both spark and fuel, and know the timing is set up correctly because while the used engine was out I replaced the belt, tensioneer, and related. Simple compression test showed 50lbs. in #3 cylinder and 100+/- in the other three. I just have trouble understanding why the engine wont at least start, even with a low cylinder? I still have to do a leak down test and find out if I might have some bent valves on the used engine or if the #3 lower end is toast. I had thought that there wouldn't be any issues with ECU going from b6 to b7 (just more valves in the head)? Anyone with any suggestions?? I have taken it to local mechanic and he thinks I don't have the timing belt on correctly, he wants to charge me another 250 to tell me if I did it correctly or notThanks in advance.