As some of you may have read. A couple of weeks ago my engine developed a knock, started as a very small tap and after 25 miles became a loud knock.
I got the car recovered to a local garage that does a lot with Imprezas and it's been there since.
Compression test shows 135 130 driver side and 95 90 passenger side, the knock seems to be more top end rather than bottom. The car lost no power, all gauges were normal and there was no smoke, however, when I lifted the bonnet after I stopped to get recovered the engine was red hot.

He's going to start stripping it down shortly but any guesses as to what the problem maybe? Head, cam?

Thanks