528e engine swap
Alright guys I need some advice concerning my 1986 528e. I purchased the car over four years ago not running from a friend for $400. At purchase the odometer read over 300k. Previous to my buying it, it hadn't ran in 2 years. We put over $1000 into it trying to get the engine running and able to pass smog. New timing chain and guides, fuel pump, radiator, hoses and water pump. Eventually we got it running but the engine felt absolutely dead. After all of this our mechanic could not get it to pass smog either due to low compression in one of the cylinders. I don't want to just get rid of it because of all the work we've put into it but the engine and drivetrain looks all but dead considering the mileage on it. My dad said he can get a used m30( I believe this is correct for 528e?) for $600. I have roughly $2000 of my own money saved up that I can put into it as well. My question is, how much money and difficulty is involved in doing just an engine swap compared to a whole drivetrain swap including tranny and diff. I have the impression that used engines and trannys are fairly affordable with the right amount of searching and I still have pretty new parts on the old engine I can salvage. But is it really worth it at all? Am I better to just save my money for some other car? If anyone has any experience/advice/suggestions I would love to hear it considering I'm at a crossroad of not wanting to get rid of something I've already put good money into or is it a lost cause at this point ?