Discussion and questions related to the course Practical Engine Building
Hi guys, I have some questions about an experience I had with my own personal EJ257 engine that I was not able to figure out exactly why my engine failed. I'm hoping maybe someone could look at the information and confirm what is was so I can avoid the failure in the future when I rebuild this engine again. So Ill dive into it with some background. The failure was a spun bearing on the 3rd cylinder (Ill have to double check if absolutely necessary) The vehicle is a USDM 2005 Subaru Impreza STi. I purchased the car with 150,000 miles with a blown engine. I had the engine rebuilt by a reputable builder (before I got into all this awesomeness) totally stock so I could get my car running. In between that point and the failure I performed all required maintenance IE oil changes every 3000 miles, fluid levels, etc. and the failure occurred just shy of the 50,000 mile mark of that rebuild. I was never all that abusive, just regular fun you can expect with an STi. Closer to the exact point of failure I was getting into some drag racing with some friends at a location we were granted the ability to do said races. We did rolls and digs and after every race I would let her run a few minutes, shut the engine down and then double check all fluid levels like oil and coolant. When the failure occurred I did a dig against a boosted Honda and returned to the staging point to check fluids, as I was about to shut the engine down a supposed "NA" Mustang called me out so of course I couldn't refuse. (I later found out this Mustang had spray) Shut the hood and lined up. We got to the end of the line and I went to turn around when the engine shut down and I was no longer able to start her. When I got it towed back to my buddies house we checked oil level it was good. Coolant good. So I started on maybe an electrical or stater issue. Turned out it was not that but when I got the car to my school (Wyotech in their high performance class) I was able to tear apart the engine and rebuild it as a project for class and we found the rod cap bearing spun up into and under the main rod bearing and the rod nearly welded to the crank. So with oil level in the sump good would it likely have been a plugged oil galley or pick up tube failure? I cant provide much after that because I was rushed in the rebuild process with class only being so long so detailed inspection was not not performed. I know the factory oil pick up tube is a weak component in this engine but the tube itself seemed structurally sound and i put a Killer B aftermarket pick up tube in the rebuilt engine but I was hoping maybe someone can shed a little bit more light. Thanks guys.
Was there any evidence of knock on the piston or head?
Without being particularly familiar with common failure modes on those engines I imagine there is a potential for oil starvation on hard launches due to oil movement in the pan but seems unlikely if you upgraded the pickup. Were any of the other bearings marked badly?
Did all plugs look the same?
do you know which injector was on each cylinder? Might be worth getting them flow tested, perhaps that cylinder was running a bit leaner and just hammered the rod bearing?
Any other evidence of bearings running hot?