The actual torque value I cannot help you with...
But always torque heads in a criss-cross pattern. Are you familar with that? It's difficult to describe on a post, so I made a quick sketch (just a start, but I'm sure you can follow through from there). It's just a sketch, but gives you the intent of the criss-cross pattern. It would probably be better to work from the center out each way, actually (rather from the corners). I've seen both methods used.
It's also important to do a progressive torque. This means you'll torque three times. The first would be at 30-35 percent of the (finish) torque value, the 2nd would be at 60-65% of that finish torque value....the third would be at the finish torque value.
The intent is to pull the head down evenly which is what the criss-cross pattern and progressive torquing provides.
Sometimes heads require retorquing after a specified number of hours too. Also, if you do find a manual and it differs from my sketches, always go with the manual!