I have a ka24de turbo that runs a megasquirt fuel management system. I purchased the car with the system, and although I am familiar with it, I have never installed one. Recently I have had troubles with my DB37 cable, and I purchased a new one. 2 days after changing my db37, I turn on my car, and hear a horrible rattling sound coming from the bottom end of my engine. I check the connections on my megasquirt relay board to make sure the engine isn’t just knocking due to misfire. The sound goes away but I am not sure if it is due to me securing the relay board or due to the car warming up.

The next day I turn the car on and hear the same sound except this time I realize that the intensity of the sound changes when I press or depress the clutch. I attempt to drive it to work but it dies on the way.

It is in my garage and I have been trying to diagnose what has happened.
The car will turn on, but won't idle and is very hard to keep alive. The same rattling sound is coming from either the bottom end or the bell housing. It is definitely not timing chain rattle.

I compression tested the cylinders, and they are ok. I did not use my analog tester because I have forged pistons, and they don't get good compression unless the motor has been allowed to warm up.

I tested for spark, and all four cylinders are firing well.

I dropped the oil looking for metal shavings, and did not see anything unusual. I did not drop the oil pan because the cross member is in the way, and I am not confident I can pull the motor without ruining the megasquirt wiring harness.

While under the car I see a very large oil stains on the underbody of the car where the transmission meets the driveshaft. I drop the oil from the transmission and there is less than a quart in the transmission. This is when I believe I found the problem.

I remove the transmission, clutch and pressure plate. The clutch still has meat on it still. I have only changed clutches when I completely destroyed them, and I am unsure if this clutch is still ok. I have included pictures of the clutch, flywheel and pressure plate. There is some minor scoring on the clutch, flywheel and pressure plate, that I am unsure why it is there, or if it is ok. There is also a very minor rattle when I shake the clutch.

I then bolted the starter back onto flywheel and attempted to start the car, but it won't start. The engine is turning but it won't start. There is also a loud of metal on metal rubbing sound, that I don’t know if is normal. Perhaps this is a normal sound that is just louder due to there being no bell housing to muffle it?

Either way, I am unsure if my problem is the transmission, or the bottom end of the car. Before I start to buy the necessary parts I want to be confident that I know what the problem is. ANY input would be appreciated. Thank you.