Pops' 1997 S6 - 07k BLK WDW

[85oceanic]

Dang man, I just saw this! Major bummer that you had some slap going on and those poor pistons. :( Bummer!

[Highlander]

Jamo has a good point. Don't B6/B7 S4s have a similar problem with the piston being too thin at the valve relief? I'd say the factory had a good reason to get rid of them on stock pistons.

Than all of us running JE should be having that problem ;D, it sort of looks like hg is sticking in a combustion chamber, can’t really tell from picks, but it is cracked same spot piston is melted

sorry to see this guys.............

Fasterthenrs2 makes a good observation about the gasket........you' got to get
those pistons out. The bores look great..........it looks to me like it could be combination
of things.........machining,possible head gasket,tune.....pretty much what everyone else said....

Damn...... :( that thing was a cruise missile at ice racing....

Cheers,

Craig

[chaloux]

It def looks like it got hot in there, few things can cause that, excessive back pressure, detonation, plus hg got lifted (that’s why by pressurizing one cylinder it was running out another one) det or misfire will do that or to high boost on a pump gas. Those pistons are toasted, if bores are in speck (not oval, and scratches are just visual etc) I be not afraid to just hone them right in a car and use it again, what hg gasket is that?? why in one of the pick. it looks like edge of hgg is broken??? You guys didn’t use 82.5mm hg on a 83mm block, I assume.

how can you tell it looks like it got hot? do you mean specifically at the "chip" or possibly melting point on cyl 1 3 5? The pistons were gold on the top to start with so that's why they have that colour. it looks pretty smooth and uniform to me other than those weird chips

I don't think the HG lifted but it if it did it would have been between cyl 4 and 5. It is 3 layer copper/metal with o-rings in the block. 83mm. I think the excessive leak through the rings on cyl 3 4 and 5 is whats causing the cross-pressurization. but the bottom layer of the head gasket did crack on cylinder 1 and 3.

So you'd use the block again (if it were in spec) after a honing? that's reassuring anyway. That's kind of what we thought - they look really clean and the "scratches" cannot be felt. just have to see what shape (har har) it's in.

And eah that piston slap is little bit on a excessive side, but with proper rings that should not be a problem, what hgg is that???? in vid you can def see its blown between cylinders

wait so you'd use these pistons again? or just saying that this amount of slap is okay with proper ring/seating.

didnt you guys o ring the block?

yes ^^

wow.

urdoinitrong... somehow.

yeah. apparently doing everything to spec and choosing high quality (and EXPENSIVE) parts = wrong. it doesn't add up

Hmm see http://www.s2forum.com/forum/showthread.php?t=5523 I had mine machined like this to remove the area around the recess

hmmmm. very interesting read. i am anxious now to see the skirts.

[chaloux]

What is the deal - can a stock MLS head gasket be bored to 83mm? Also we'd have to use another copper one because of the orings. Guh.

Putting the standard block in with stock pistons is just so easy

[Repaair]

Take the pistons and block to another machine shop and have then measure
the pistons and put a dial bore gage in the cylinders. Seems kinda loose, I think
JE specs are about .004"-.005". Its the only way you will know if it was done right.

[fasterthenrs2]

Cant use the pistons you have they are tosted, get them out of block, it will tell more of the story. Hg got lifted no doubt a bout it, who did o ring job, and how much they sticking out above deck surface??? Was that 034 hg?? That coating those bring melting point a lot higher, but if you look at valve relives they bubbling up. And if hg metal layer was sticking in a bore( from picks it deff looks like it did do that, it will act as a glow plug ( that steal layer is 2.5 thousands thick) do you have picks of the o ringed block??

[chaloux]

FYI - Pauter rods will not come up through the block, and the oil pan can't be removed with the 7A flywheel on.

[ringbearer]

How about some salt for that wound.

No fun

[Repaair]

That whole motor has to come out. Bummer

[fasterthenrs2]

i have done many oil pans with 7A FW, it has a service relieves, you just need to spin engine around to line them up with last two bolts, use swivel 10mm socket or 5mm alan (depends on a bolts you used) and done in few min. pauter rood bottoms r bigger then 83mm bore??? Sounds pretty unbelievable to me

[PRY4SNO]

i have done many oil pans with 7A FW, it has a service relieves, you just need to spin engine around to line them up with last two bolts, use swivel 10mm socket or 5mm alan (depends on a bolts you used) and done in few min. pauter rood bottoms r bigger then 83mm bore??? Sounds pretty unbelievable to me

What he said...

Just turn the crank so that the service reliefs in the flywheel line up with the bolt holes, and you can pop that sucker off in no time. Well. As long as it takes for you to remove something like 13 bolts.

[123quattro]

Take the pistons and block to another machine shop and have then measure
the pistons and put a dial bore gage in the cylinders. Seems kinda loose, I think
JE specs are about .004"-.005". Its the only way you will know if it was done right.

I have Diamond Racing pistons in my 3B. I'm running 0.0075" clearance. It's been together now for about 15,000 miles running a AAN hg. The engine doesn't make any noise. Piston slap is much more prevalent in V configuration engines. Sorry that yours got hurt. :(

[Katman]

I dunno.. But doesn't it look like the headgasket is a bit distressed between ALL of the cylinders?

Not sure what that would mean though..?

[chaloux]

We're now talking with JE/034 to figure something out. I really don't think detonation is the issue here, but I could be wrong, I am not a mechanic or guru. The car was tuned on the dyno with knock sensors and basically ran that tune since. 26psi with 8.5:1 and water/meth should not be detonating. The head gasket is an 83mm head gasket. The bottom metal layer is cracked where the piston started coming apart on cylinder 1, 3, and 5. In retrospect I think 83mm is too big for a ringed block, but there is no evidence of gasses passing through cylinders at the head gasket. That bottom layer of the HG definitely got hot, but did not crack until dad pried at it. That thing was stuck down like crazy!


Did some measuring today. JE asks for .003" clearance. Was bored to .003"

Except these pistons have worn from 3.265" to 3.260"

Comp rings are damaged. On numerous spots on all of the comp. rings it looks as though the top and bottom edges are fine but it has chipped out in the middle. One ring, cyl 5, is broken. Two are seized. The ring landings are scraped on the outmost edge as well.

We're not sure what to make of it. Faulty rings? The pistons wreaking havoc? 92.8 crank? Detonation? At this point we're not sure and may never know.

So, moving forward - what to do now? The way I see it, we have 5 options:

1) new 83mm JE pistons for 92.8 crank, same block, new copper HG
2) use our 83mm JE pistons for 86.4 crank (9.3:1 comp ratio), same block, new copper HG
3) put in a stock block with stock pistons and either SCAT/Pauter rods
4) new 81mm JE pistons for 92.8 crank, stock HG
5) new 81mm JE pistons, stock block, stock HG

If JE were to send us a new set of pistons I think we'd IDEALLY get them a) machined so this doesn't happen again, b) have them set for 8.1:1 comp ratio to allow more boost to put the turbo more in its sweet spot, and c) run a 92.8 but 81mm setup for a 2.4L stroker

[crappyoldaudis]

I think you should buy a Honda

[chaloux]

Here's a pic of the ring damage. It's BIG so link only.

And here's a picture of the skirt damage as well as the ring wear. You can see it's dragged the ring landing down by scraping on the block (look right in the middle of the piston just to the left of the light glare.

[thetatau87]

That looks like detonation to me. The small pits just above the top ring and around the area of the piston that is missing at the valve relief look exactly like every other piston that I've seen come out of a motor that had detonation. Once you get detonation all kinds of bad things start to happen and they can happen really fast. Hard to say if detonation caused all the other issues with the piston wear and ring damage, but it's the most likely culprit.

[fasterthenrs2]

As above stated, that is a detonation or just a massive back pressure resulting extremely high egts, and rings do not seize in ring lands, the piston has got so hot or detonation has crushed top part of it down resulting pinched or broken rings, like I said before those coating do work that’s why it is no obvious detonation signs, piston cannot wear down 5 thousands, is the bore still in a spec, ask JE can it be pistons after getting extremely hot and then cooling down will shrink at all. Who made hg?? Did the metal shims where bored to 83mm?? The hg will not crack like that just because it was stuck, from another side if it was in combustion chamber that can def happen

[chaloux]

Perhaps some of the runs with the QSV not operating correctly/stuck closed caused it? A .42 A/R would definitely create some backpressure once full boost has been reached.

The bore is still in spec. I don't know Janis, the new piston was 3.265, these are all 3.260. The HG is from 034 - their multi layer copper with o-ringed block. It is an 83mm HG. It doesn't go into the combustion chamber, it is flush with the bore.

[Highlander]

Perhaps some of the runs with the QSV not operating correctly/stuck closed caused it? A .42 A/R would definitely create some backpressure once full boost has been reached.

The bore is still in spec. I don't know Janis, the new piston was 3.265, these are all 3.260. The HG is from 034 - their multi layer copper with o-ringed block. It is an 83mm HG. It doesn't go into the combustion chamber, it is flush with the bore.

While looking at the exhaust manifold runners, do the damaged pistons look like they
would have been more affected with the QSV being shut on that half of the turbo housing?

I think your on to something with this theory.

Cheers,

Craig

[crappyoldaudis]

wow, pistons shrank 5 thousandths? You have invented the shrink ray! Don't point it at my pants.

[123quattro]

What turbo and how much boost are you running? I have a 3076R, 8.5:1 cr, 7A cams, a nice tube header, and run about 28 psi on 93 octane pump gas. I haven't had any detonation issues. I think you have.

My pistons are 82mm and work with a stock MLS gasket. If you swap blocks, I would stay away from O-ringing the next one and skip the copper gasket. I don't think you need them and it just complicates the situation.

[Hank]

I am with the others. That top bit of the piston looks like detonation to me. Like Janis said, rings just don't do that unless there is serious heat/detonation events. This explains the head gasket as well. No gasket is going to be particularly thrilled to see the crazy high pressures induced by good old fashion detonation. If it is powerful enough(and hot enough) to bend over rings, it is powerful enough to give the gasket a run for it's money. It doesn't look like it failed though, so that is promising for my copper composite gsket in my car.

[fasterthenrs2]

Perhaps some of the runs with the QSV not operating correctly/stuck closed caused it? A .42 A/R would definitely create some backpressure once full boost has been reached.

The bore is still in spec. I don't know Janis, the new piston was 3.265, these are all 3.260. The HG is from 034 - their multi layer copper with o-ringed block. It is an 83mm HG. It doesn't go into the combustion chamber, it is flush with the bore.

can you take pick of hg straight on??? Il pm you some picks (if I can find them) I didn’t use in my motor

[chaloux]

We'll concede that there was definitely some det going on. I guess the question is what caused it? My guess is the QSV being closed once full boost has been achieved. We were boosting to 26psi (28 for a tiny bit but that didn't last long and was barely driven) with 94 octane ONLY and water/meth while being monitored in VEMS with good AFR.

We won't be o-ringing the next block.

So I guess it is critical that the QSV operates properly. Sorry guys, no more open vs. closed comparisons! I think we all know it works to the tune of ~900rpm on a 2.5L. Which is astounding, really.

Until we know what's going on with JE, we'll have to wait to put another bottom end together. I have a feeling we'll be putting a stock bottom end with rods and bearings in pretty soon, but I wish we could do 81mm with 92.8 crank. Dang expensive custom pistons!

So what are everyone's thoughts on CR dropping head gaskets? Obviously dropping CR with pistons is more ideal, but is it so bad to use a HG to do it?