I hope you used a torque wrench to tighten the screws. They only need to be a little bit more than finger tight.
The other thing is did you check the oil filter for the 4 little holes at the other end? If the holes aren't there the head doesn't get any oil and you can trash it very quickly. If you don't know take out the oil filter and check it. Please!
When you post what you found wrong we all learn. Thanks.