Engine work

[driveslikejehu]

Maybe more of subie forum question... Pulling the heads for gaskets and hopefully not much else.
Then I found some minor scoring in cyl 2. (see pic) It's been a minute since I did cylinder/piston work. I'm wondering if I can bore/hone out the offending cylinder .010" and get +.010 rings and maybe a stock piston.
Alternatively, its .030" over for all four and 4 pistons and rings?
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[Bicyclops]

I wonder if .010 is going to clean the bore up. That piston has a lot of wear on the skirt too. In an oversize bore it will rock even more. Seems to me that if you are going to bore, you should provide oversize pistons to the machine shop so that you get a good fit. As much trouble as it is to do an engine change on an 818, I sure would want to do the overhaul right so I didn't have to do it again anytime soon. I was absolutely sick when I spun a bearing on my 1000 mile new engine on the dyno.

Ed

[Grubester]

Bicyclops -- Sucks that a new engine has this problem. Was it a purchased crate engine? I've seen the odd sad/horror story on the forum with serious early engine problems.
Not sure what to expect with my BPE 347 that I will start up for the first time a couple of months. Sure, there are the various comments of people experiencing problems, but as an ex-QA Mgr., I have to wonder what the defect rate really is. I'm used to dealing with PPM failure rates for units. And I hear BPE has a great warranty, but it's the having to deal with tear-downs, engine removal, etc. Ugh.

[Railroad]

My choice would be: Hit that cylinder with a hone, no boring, check the bore diameter for piston clearance, buy piston with right clearance, weigh and match the piston weight, new gapped rings, check wrist pin movement, put it together and go.
Not for everyone, just me.
Good luck,

[driveslikejehu]

The engine is stock from a '06 STI with over 107,000 on it, so not feeling too bad about its performance. No ring land probs or valve issues. Probably an overheat somewhere in its life or possibly some debris.
I'm considered going with a short block, but I enjoy the work so probably just rebuild this one. Not interested in a "build" at this point; power is not my lap time problem, lol.
I found it be pretty easy to pull the engine/trans; especially compared to a real car. Easy to remove the rear body parts then fairly wide open.
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[Bicyclops]

Howdy Grubester,
It wasn't a crate engine. It came out of my 02 donor with 225000+ miles on it. I didn't want to have to install it twice (Ha!) so I had the Subaru tune shop I had selected overhaul it. It sounded like they did it right - new STI crank (2.14L stroker), pistons to get the CR right, racing bearings, ARP studs, etc. I had them setup the heads and I installed those along with the pumps and timing belt. I upsized to a Blouch turbo and large injectors for E-85. I tried to break it in right, limiting RPM, staying out of boost, avoiding lugging. Had about 775 miles on it when I brought it in for tuning. He reported that after adjusting the tune, he got less power out of the next pull. You could hear it knock at idle with a little clutch disengage. Not good. It ate a rod bearing. All I can think of is that the assembler didn't check all the sizes on brand new crank and bearings. I think the tuner actually farmed out the build. Between him and the engine shop, they agreed to make the bottom end good for me and even trailered the car home to me so I could pull the engine and bring it back. I couldn't believe the amount of 1/16-1/8" copper colored chips in the oil! Since I had gone with a dry sump, I had to take the pump back for inspection and flush all the hoses, and flush, and flush, and flush. What a nightmare. The happy ending is that, after I broke it in again (very carefully) for a thousand miles and changed the oil to Motul synthetic, he tuned it on pump gas and again on E-85 and it runs absolutely great with tons of power (386WHP, 367lb/ft). Pay attention to break in instructions and you should be fine. I just had a piece of bad luck.

Ed

[Bicyclops]

Howdy Jehu,
An overheat usually warps the block and/or heads. It's why Subies have a rep for blown head gaskets. From what I've read, very sensitive to oil starvation and low coolant, that and lugging. Better check for flatness.

A hone, piston, and rings might work. I don't think oversize rings on a stock piston are the best idea. Wrong radius circle for the bore.

Ed

[driveslikejehu]

Ended up doing new pistons, one size over-bored. Has been a great winter project.
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One new valve, the rest lapped in. A few exhaust valves took enough work that the clearance is off. So I'll measure again after heads are bolted on and get new buckets.
Latest fun was making a rear seal tool from a PVC cap.
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[J R Jones]

My 818 engine came with the unfinished kit. It was a 2002 WRX with 132K miles. I tested compression/leak down finding one low cylinder and leaking from an exhaust valve. I read that head cracking can cause that. I sold the engine on Craigslist, good enough for the street.
I have installed an Acura V6 that tested very well. Injectors leaked and the PCV system was coked-up from a bad PCV valve.
jim

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[aquillen]

JR - looks like I'm about due to come and see your progress in person - looking better every day...