Actually, the two engines are exactly the same. The head is turned around on one of them lol. They are both OS HZ-H engines (I want the -R!). The reason the one head is not black is because that is the one I had to heat up with the torch to get the head off of to find all of the internal damage. The one on the left was Gaba's engine and it's perfect in every way. The one on the right runs and runs pretty good but has some damage inside it. But, both run.