Need help diagnosing 240sx

[Bkahl]

I just got an sr20det s13 and I was doing pulls with a buddy and his 5.0. Everything was going fine but after the 2nd pull. I slowed down and noticed when I gave the car throttle it didn't fully gain speed it just kinda built up boost but didn't do much accelerating. Which led me to believe clutch or transmission. At this time I noticed the engine was super hot as well. I started to notice a knocking sound as well. From in the car it sounded like it was from the transmission but I can't be too sure. The knocking is present at all times unless I have the clutch engaged. But if I have the clutch engaged and still rev the car knocks. I got it home let it cool down. I turned it on and gave a little gas and could still hear the knock. So I shut the car off and went to start it one more time and the starter didn't even make an attempt to start. But the battery had 10volts when I was trying to start it.