I just completed my first rebuild on my 95 Mustang 5.0 everything went pretty smooth and the car started right up and idled great. However, when I push the RPMs up I get a very bad vibration. This happens in neutral as well as driving down the road so that should eliminate anything to do with the drive shaft. After doing some research I think I might have made a rookie mistake...... Almost all of the parts in the engine are new with the exception of the block, the crank, and the connecting rods. The mistake I believe I made was not having everything balanced together. Everything I purchased was balanced at 50oz, but I've been told that even if they are balanced the same, they still need to be balanced together by a machine shop. One additional thing to note, I did NOT have the machine shop line hone the mains/crank (Another no no) and when I got it back from the machine shop the crank was pretty tight, but I used thinner bearings and everything checked out with plastigauge. Can anyone weigh in on if I'm on the right track or a possible solution? I have removed, cleaned, and reinstalled the harmonic balancer and there was no change. Thanks!