Some details:
I bought the car in April, and the night I got it here I broke a rocker arm on the 3rd cylinder (exhaust). It sounded like a bad coil (WRX sound) as the exhaust valves weren’t opening on that cylinder, so I spent a day or so troubleshooting, changing plugs and injectors and coils, etc.
When I found the broken rocker, I found the rocker retainer, but never found the valve shim. Some friends of mine who have built engines more than once advised that because I didn’t find it after flushing 2 oil changes through, it was probably lodged somewhere safe and I shouldn’t go through a tear-down just to look for it.
I replaced all 8 of the rockers, and after I had the car running again, I did a compression test and a leak down test, as I was getting some gas in my oil. The compression numbers were pretty even across the board, cylinders 1, 3 and 4 were about 120, while 2 was at about 110 if I remember correctly. I figured that the aftermarket pistons could account for the numbers being below the usual 140 that I see in threads, but because they were all within 10%, it should be fine to get me through the rest of the season.
The leakdown test stayed in the “green” range on the tester, not perfect, but again good enough to get me through the season.
I figured that my 1/4 mile times would give me an indication how strong the engine was, and my best this year was a 12.9 in July at 106mph. This was slower than my 112 mph 13.1 in June with crappier tires, but still…12.9 is respectable. I knew that with the dyno graphs I had seen for the car, I should have been in the low 12’s, but I wasn’t far off.
I broke a rocker on the 1st exhaust cylinder again at the beginning of August, and it took some things with it. Namely the aluminum dowel that keeps the timing chain on the crank gear when you drop it from the cam gears, and the rocker retainers, etc.
I figured that this is what damaged my timing chain, as there is some minor cosmetic damage around the outside of the chain and one kinked link. If the rocker had “jammed” on the aluminum dowel for a moment before breaking it, it could have easily done the damage.
The timing chain was the main reason for this re-build. I knew that I had some bottom end issues, what I though was a possible washed out piston from the rocker arm issues and troubleshooting that I had done. I figured new rings and I’d be golden. Nothing serious. However I was getting a lot of smoke/blowby from the valve cover breather as of late, so this re-build was definitely needed before the end of the season.
I did a compression test before I pulled the motor this weekend.
Cylinder 1 120
Cylinder 2 49
Cylinder 3 115
Cylinder 4 108
My battery was dying and the starter was having troubles, so I figured #4 should be a little higher with a decent crank.
Obviously cylinder #2 is in trouble.
I was hoping that the rings were just shot.
Now I find this:
3 of the pistons are beautiful, besides the carbon built up in the middle, it basically wiped off.
But check out piston #2.
It’s destroyed!!
The dark side looks like some pieces are broken off…
The light side looks like maybe possible detonation, but I don’t think so, because the marks/pitts are pretty big, and it’s right on the edge of the cylinder.
Is it possible that the valve shim from April made its way from the head to the combustion chamber some way? I have no idea how it would…
Is it typical for detonation to occur on one cylinder, and only at the edge of the piston?
I should have heard this, or my “knock control” should have picked up on it.
You can see the damage on the head as well.
To add to this, my effin GT2871R is toast. There’s crazy play in the shaft (axial), so I have to deal with that as well. Can you buy rebuild kits for BB turbo’s, or do you need to buy a whole center section? I guess either way it’s going to be expensive.
So Polar…no, I won’t be putting the same internals back in…
Sorry for the long upload times, my damn internet connection is in/out all the time.
If anyone can give me some insight, please do so.
props bro
you a cool dude!!
