As the title states. I had finished adjusting the first intake valve lash and tried torquing it to spec and the bolt snapped. Should've known better than to use the torque wrench in the first place. Broken bolt head sank into the engine oil, and I'm not sure what to do now. Any advice?

 

1) Find and remove the broken bolt head.
2) You will have to remove the broken bolt. If it is protruding you might be able to grab it and unscrew. If not, you may be able to use a bolt extractor, or you will have to drill it out and then clean up the threads in the hole.
3) You need the torque wrench to get the proper torque; you also need your torque wrench to be accurate. Most can be calibrated using relatively simple procedures that you can find in various Youtube videos.

This is just my assumption, but I have always thought that a given torque wrench is more likely to be accurate in the middle of it's range. In other words, I wouldn't use a 1/2-inch 10-150 lb-ft torque wrench to torque critical bolts to 10 lb-ft.