I've searched the threads trying to find an answer to my problem and I was unable so here it goes. Two weekends ago I began to tackle the job of replacing head gaskets on my 2000 blazer with the 4.3 vortec motor. After many long nights after work I finally got the car running again during the first test drive the car had random miss fires (verified with OBD scan). I replaced the distributor with a known working one and the now the vehicle will crank with no start. I checked the timing and it is correct. Just for wits and shiggles I put the old distributor back in and the motor still will not fire. I've checked fuel pressure which is within specs and am getting fuel to the motor, checked the ICM and the coil which are both good. I'm getting spark in all cylinders as well. During the first test drive (when it had random missfire) the tachometer was not working which did work before the project was starting. Not sure if it has anything to do with the no start though. Any help or information would be much appreciated.