about a month ago i bought a engine that i thought was a si for a 1990 crx. I blew it the othere day and saw that it had zc stamped on the block. The head is good so im just going to throw another block in there. But here is my problem, does the zc mean that it is in fact a zc or does that mean something else and if it is a zc can i put an si block on the head. If not what are the differences. thanx a lot

 

As long as it is the sohc zc your plan of action will be fine. The SOHC ZC is basically a japan only version of the d16a6 here in north america.