This all seems to stem from an user error made a few months back. I did not tighten the CAS retaining bolt after adjusting my base timing. The sensor shifted far as possible at the worst possible time. I knew I fucked up when all the sudden I had a subaru exhaust note in the middle of a 3rd gear pull. my heart dropped. Although it still "ran", the poor thing was burning oil ever since. So I put it away and finally got it all apart.

Beyond the missing chunk of piston, what about the detonation? how long does it take detonation to damage the piston like this? Could it have been from the single incident or is it symptomatic of a longer term issue? The pistons in cylinders 2&3 also had some minor det signs but nothing close to this. Cylinder 4 had none that i could see. The engine is stock and I am running a TSE kit with the stock WG about 12 psi on my gauge. i'm using the base timing map from trubokitty... Its got about 10k miles in this state and has 4 track days with the turbo. The other embarrassing thing is that I unwittingly ran the car at thunderhill after this incident in 110* ambient temps, so maybe some of this happened at that final track day. Please hit me over the head with some some feedback!

side note: any machine shop recommendations in the bay area?

carnage

 

What city?

 

i'm in the walnut creek area.

 

similar thing happened to a buddy of mine. Had been playing with his tunes and had two different project files made. Forgot the timing sync # was fairly different between the two, when he switched to a different project file the advance in timing almost immediately blew one of his stock pistons ringlands very similar to yours but worse.

But with cast repeated detonation will eventually take out the piston, but severe detonation will take it out very quickly.

 

Main machine in concord or S&S in San Leandro. I believe TriValley (PH) closed many years ago and I'm not sure about Morgans in WC.

 

Got it. This does seem like a common location on the piston to give up. I've seen several photos now of similar failures. it sure did take this one out quick!


thanks for the machine shop suggestions! any chance you know if one of these guys have a torque plate for the bp engine. The shop I called in antioch was so booked up they basically said just call back in three months and they might have time for me... I guess business is good!

 

Trivalley might since they used to do Rebello's work. I would call Main first they might have one or can borrow one.

 

Cool, appreciate the advise. This is my first time going through this process. Robello was the shop I called in Antioch, they came with a great reference. It seems they're super busy and/or uninterested to work on these engines. I'll give Main a call tomorrow.