My DD '08 Subaru Legacy (N/A EJ25/ 5 speed) lost all compression in one cylinder. Pretty sure I toasted a valve or had the valve guide slip issue occurr. I've got a bore scope arriving tomorrow to see what's what. Assuming it's a head issue... I'm hoping to fix this car on the fast and the cheap. (I really like the car, but realistically, long term it will probably make the most sense just buy another one in better condition, these cars are really thin on the ground with manual trans, so it's going to take a long while to find a nice one. I'd like to limp this one along while I look for a replacement.)
There's a dude selling a complete EJ25 engine with rod knock but pretty low mileage- 125K? . I'm tempted to buy it to snag the heads, but I have to wonder if the same issue that caused the rod knock (presumably run low on oil or poorly maintained) is going to mean that the heads are jacked too. Galling of the cam bearing surfaces? Lots of bearing material packed in the oil passages which will ruin my engine? I know no one can say for sure, but is this a terrible idea or a reasonable one?
A spun rod bearing resulted in galling on the cam bearing surface of my Dodge Neon. (2.4t)
OR oil feed issues resulted in the spun rod bearing and galling. (hard to say really, but a possibility to consider in your case as well)
YMMV.
Depends on what caused it, if it was run low on oil then the valvetrain will probably be ruined too, which should be easy enough to see with the cam covers removed. If it was something specific to the bottom end and it wasn't run long after failure you'll just need to run it all through the parts washer to be sure there's no debris from the bottom-end failure in there.
Thanks for the info! Sounds like the consensus is that the heads might be dubious. Maybe it would make more sense to fix the heads that I have depending on what I find with the borescope. If I have to buy the used rod-knock engine, maybe I'll lowball the seller knowing that I might be buying junk heads- I doubt he'll let me disassemble and inspect them.
I've been through a few EJ25s with spun bearings. It's hit or miss on whether the heads are good. There will likely be some scoring on the cam and bearing surface in the cylinder head. If you have cam phasors they are potentially packed full of bearing material on the donor engine. Also, every single time I've replaced a short block I've found the heads need some machine work (typically decked, valve grind, and sometimes guides)
EJ longblocks with rod knock are super cheap because there are so many of them. I don't think it's unreasonable to ask the seller if you can pop off the valve covers before purchasing.
