Lost Compression in cyl 7&8 Mystery Solved!

[pro 5.0]

I have actually done destruction testing on these motors.


1) If you force detonate them... you break the top of the piston.

2) Heat from long duration pulls (and low timing, due to high boost) kills the middle ring lands (like this image)

3) Not enough or too much fuel = melted stuff.



Trust me, I have broke things in the name of science.

When you say long duration pull is that like going a constant speed of 160 mph in 5 th or 6 th gear, or are we talking from a roll in say second gear and running through all 5 speeds until redline then backing off.

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[Barrel]

When you say long duration pull is that like going a constant speed of 160 mph in 5 th or 6 th gear, or are we talking from a roll in say second gear and running through all 5 speeds until redline then backing off.

Long duration of WOT. I'd guess in excess of 15+ seconds under boost and WOT operation, like 1/2 and full mile racing or Mexican streets.

 

[HISSMAN]

If I had just looked at the pistons I would have thought...Another STi ringland failure. It looks like you have a great build going though. Good luck!

 

[SVT-DADDY]

Sorry for my ignorance but would meth injection help prevent the heat issue that's causing ring lands to break?

 

[JC500]

This is a awesome thread. Love all the pics! I am going to get meth for my Roushcharged coyote for sure . I beat it hard sometimes and just knowing the meth is there for cooling only in my situation would make me feel better . I think meth would be a great aid

 

[Crackerjack17]

Very nice. What did that set you back if you don't mind. I am going that route once I am back on the mainland.

The shortblock was on sale for Christmas time so around $6k. All those extra parts were over $1k. I'll add it all up and list a total when I get the chance. Little crap adds up. Arp flywheel bolts, new crank pilot bearing. Plus I just bought a mcleod rst, even though my clutch was holding decent and actually looks in really good shape.

I'll admit a bunch of this is overkill. I could have used my block and likely h beams would have been more than adequate. Also, the billet chain guides and their $200 tensioners are Un-needed. But, oh so pretty. Billet rear main cover wasn't needed or the machined crank trigger wheel. Lol. I got carried away ordering.

I am going to reuse my stock heads. They look great. Should I upgrade the intake springs? Does the gen 2 motors have the old boss 302 valve springs? I haven't asked anybody about the heads yet or if I should change anything while it is apart. I plan on e85 and turning up the p1sc1 and possibly send it in and upgrade to D1X.

 

[Crackerjack17]

Long duration of WOT. I'd guess in excess of 15+ seconds under boost and WOT operation, like 1/2 and full mile racing or Mexican streets.

Everything. Lol. I ran it wot several times every time I drove it. Easy to hit 140 without even thinking. The 160 runs were to red line in 5th and then let off. But, where i live we do have a several mile uphill highway and late night runs wot at over 140 for a few miles were not uncommon. A good friend has a 2 liter honda laying down over 800whp. At 120mph he pulls away like I threw a parachute out. His car is 2700 lbs. Crazy. Lol

 

[Crackerjack17]

No tuner could have saved that motor.

Typical tight ring gap + highway pull = heat failure.




The only thing getting old about seeing these failurs, is all the tuners throwing other tuners under the buss. (and the FB group guru's chiming in)

Nothing in the ECU says "Save piston from .009 ring gap" :lol:

:cheers:

Yeah, this isn't a tune issue. I reviewed all my own logs and I also recorded logs frequently and looked at them. I was having some issues with false knock in the beginning. That dang a/c bolt on the headers was one issue. But I likely got some less than stellar gas at times too. I ran a good bit of octanium at times, but not all the time. And when I did, I only added one can to the full tank instead of 10 gallons, to try and buffer the octane a tad.

Those ring lands between the rings and oil control rings are thin. The top of the piston to the first ring is much thicker.

 

[Barrel]

But, where i live we do have a several mile uphill highway and late night runs wot at over 140 for a few miles were not uncommon.

Should I upgrade the intake springs

Man. That Stage 2 intercooler putting in work then lol. Also, I'm on completely stock heads and springs and I spin to 7500RPM. If you're not pushing past me for power/RPM stock springs should be fine.

 

[ahl395]

Thanks alot for posting this, good info here and cool to see the pictures.

What were the compression numbers?

I have actually done destruction testing on these motors.

2) Heat from long duration pulls (and low timing, due to high boost) kills the middle ring lands (like this image)

[MENTION=11041]ProChargerTECH[/MENTION] , it's my understanding that low timing makes more heat and higher timing helps evacuate the heat out of the cylinder. Is this why you used that example? High boost and high timing would be slightly better, correct?

Sorry for my ignorance but would meth injection help prevent the heat issue that's causing ring lands to break?

IMO, yes it will help. This is the main reason I went with meth injection, lowers cylinder pressures and temps, helps avoid knock/detonation, and as said above I believe it also helps lower temps by allowing more timing. But again, it will only help, with a long enough pull and enough heat even meth or E85 probably wont save a stock motor. This is why I'm holding off of 1/2 mi racing even with the methanol.

Not done tuning my meth yet, but according to the calculated Cat temp sensor I dropped from 1800F to 1600F exhaust temp on WOT pulls. Which indirectly means less heat in the cylinders and on the rings.

 

[z06psi]

The shortblock was on sale for Christmas time so around $6k. All those extra parts were over $1k. I'll add it all up and list a total when I get the chance. Little crap adds up. Arp flywheel bolts, new crank pilot bearing. Plus I just bought a mcleod rst, even though my clutch was holding decent and actually looks in really good shape.

I'll admit a bunch of this is overkill. I could have used my block and likely h beams would have been more than adequate. Also, the billet chain guides and their $200 tensioners are Un-needed. But, oh so pretty. Billet rear main cover wasn't needed or the machined crank trigger wheel. Lol. I got carried away ordering.

I am going to reuse my stock heads. They look great. Should I upgrade the intake springs? Does the gen 2 motors have the old boss 302 valve springs? I haven't asked anybody about the heads yet or if I should change anything while it is apart. I plan on e85 and turning up the p1sc1 and possibly send it in and upgrade to D1X.

This will be a project for me come Jan of '19. I will be doing the F1A though.

Thanks for the info.:cheers:

 

[Crackerjack17]

Man. That Stage 2 intercooler putting in work then lol. Also, I'm on completely stock heads and springs and I spin to 7500RPM. If you're not pushing past me for power/RPM stock springs should be fine.

That's one thing I love about the procharger. That intercooler is awesome. IIRC, I never saw more than a few degrees above ambient most of the time. Would have to double check the logs for temps near red line though.

 

[Crackerjack17]

Thanks alot for posting this, good info here and cool to see the pictures.

What were the compression numbers?

1 - 230
2 - 225
3 - 220
4 - 240
5 - 235
6 - 210
7 - 105 - boom
8 - 140 - boom

 

[olaosunt]

Thanks for the details ! I wish I could turn my own wrenches like you (probably spent enough on engine labor for my multiple failed motors to by a 5.2 alluminator XS .lol)

You can probably sell your old block for a few $ hundred . I would have bought it for one of the "spares" I had built and sleeved by BES . I ended using a new bare block cause one of the old blocks had a crack in the valley .

 

[pro 5.0]

The shortblock was on sale for Christmas time so around $6k. All those extra parts were over $1k. I'll add it all up and list a total when I get the chance. Little crap adds up. Arp flywheel bolts, new crank pilot bearing. Plus I just bought a mcleod rst, even though my clutch was holding decent and actually looks in really good shape.

I'll admit a bunch of this is overkill. I could have used my block and likely h beams would have been more than adequate. Also, the billet chain guides and their $200 tensioners are Un-needed. But, oh so pretty. Billet rear main cover wasn't needed or the machined crank trigger wheel. Lol. I got carried away ordering.

I am going to reuse my stock heads. They look great. Should I upgrade the intake springs? Does the gen 2 motors have the old boss 302 valve springs? I haven't asked anybody about the heads yet or if I should change anything while it is apart. I plan on e85 and turning up the p1sc1 and possibly send it in and upgrade to D1X.

I would be careful with that billet crank trigger wheel, there was a tech video on the Palm Beach Dyno Facebook page. It explained how they were having problems with the engine revving past a certain rpm with a billet trigger wheel, they changed it back to stock and the problem was solved food for thought.

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