I forget the engine but he had the 3/4” bar on the crank bolt and had to use the front end loader to push down on it. That was a scary amount of stored energy waiting to pop.
GM aborting move to 0w-40
- Thread starter dbias
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If I understand the science correctly, the higher 40w oil should have a thicker film or boundary layer of lubrication at operating temp. If the issue is surface finish (picture mountains/valleys) ...and that finish making contact with the bearings/crank journal...a thicker film might be able to separate the two parts/surfaces and could, in theory, fix the surface finish issue (keep the mountains/valleys from touching one another).
That said...it sounds like the surface finish is just one of the problems as the sensor is looking for the crank being out of alignment or position.
All that said, the motor was built around a 20w oil at temp with oil pump engineering and passageways created to flow the requisite volume of 20w. 40w could introduce a pressure/volume issue, depending on how sensitive that system is.
They went to 40 weight to slow the failure rate down so they could play catchup.
OVERKILL
$100 Site Donor 2021
Apparently, there are also issues with the replacement engines:
(single anecdote here noted, so take that into consideration)
(single anecdote here noted, so take that into consideration)
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- Mar 10, 2021
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ive seen multiple post of folks on their 3rd engine.
I don’t get that. GM discovered an issue with manufacturing on the first engine. So then in their infinite wisdom, they replace the engine with another built with the same faulty parts. Which, surprise, fails the same way again. Onto #3…
My takeaway from that scenario is that they don’t know what’s good/bad in their parts stockpile. Which is pathetic.
Haven’t you heard, it’s the 0w20. There’s no sense in replacing the engine and using the same thin oil.
What do you call repeating an experiment over and over expecting a different result?
This simply proves if abnormal conditions occur a w20wt is toast.
Any competent engineer knows 40 wt. protects better than a 20 wt.. The question is it needed? In GMs case..yes
Any competent engineer knows 40 wt. protects better than a 20 wt.. The question is it needed? In GMs case..yes
Engines are designed to use a wide range of viscosity - just like all engines are. Many engines used in the USA that spec xW-20 will spec a wide range of viscosity in those same engines used in other countries. And they must be designed and manufactured correctly to be able to reliably use the thinnest recommenced oil viscosity.
As the oil viscosity becomes lower and lower, the engine needs to tolerate it and not become damaged from an ever decreasing film thickness between moving parts. But apparently these GM engines weren't able to use the specified 0W-20 over the long run. It sounds like it took tons of miles for some of these engines to get very worn or fail. GM wouldn't be putting 0W-40 in the engines deemed not needing replacement if it was going to cause a problem. Going higher in KV100 doesn't cause problems, but going too thin can. They put 0W-40 in them to give more film thickness between parts to help mitigate wear. It would be interesting to see some of the engines GM deems to be "OK" and needing replacement torn down to see the level of wear on them from running the specified 0W-20.
wemay
Site Donor 2023
"Ohhh Bluuue"
As a former QE I would need more information to draw that exact conclusion. I mean sure maybe but let’s see the drawings and materials and ALL the guts which of course we never will
I’ve had some OOB failures for stuff at home over the years and interfaced pretty deeply in companies but not once was a true root cause divulged
And I have been on the inside so to speak when the customer absolutely knew the root cause and true corrective actions and my erse was held to the fire!
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True, more information would be helpful.
I think the most telling damage is the crankshaft hitting the block.
Like Eric said, if the crank moved that much, it put the rods (and bearings) at an angle, and then caused the toastiness in the rods/bearings.
Wonder if the crank being out of the spec is the root cause of all these failures.
"Why the LT2 Avoided the L87’s Recall Issues
• Manufacturing Window: The L87 recall is tied to a specific production period (March 1, 2021–May 31, 2024) with defective components from suppliers. The LT2, produced for the lower-volume Corvette, likely used different batches or suppliers, or benefited from stricter quality control. GM’s 2025 L87 engines are also exempt from the recall due to manufacturing improvements, suggesting the LT2 may have been built with similar or better processes.
• Oil Viscosity: The LT2’s use of 0W-40 oil from the factory aligns with GM’s recall remedy for the L87, indicating that higher-viscosity oil may reduce bearing wear. The L87’s initial 0W-20 specification may have exacerbated issues in defective engines.
• Application Differences: The LT2’s dry-sump system and performance-oriented design reduce stress on components during high-RPM operation, unlike the L87’s wet-sump system, which faces different load patterns in truck applications (e.g., towing).
• Production Scale: The Corvette’s lower production volume (tens of thousands vs. nearly 600,000 L87-equipped vehicles) means fewer opportunities for defective components to affect LT2 engines, and GM may prioritize quality for its flagship sports car.
Conclusion
The LT2 V8 in the 2025 Corvette differs from the L87 V8 in GM’s recalled trucks and SUVs through its performance-oriented design (dry-sump, shorter intake runners, higher horsepower), use of 0W-40 oil, and apparent exemption from the manufacturing defects affecting L87 engines from 2021–2024. The L87’s recall stems from faulty connecting rods and crankshafts, leading to engine failures, while the LT2 has no reported similar issues, likely due to different production processes or quality controls. Owners of L87-equipped vehicles should check their VIN on GM’s recall lookup website for inspection and repair details, while Corvette owners can rest assured the LT2 is unaffected by this recall."
https://www.corvetteforum.com/forum...921439-6-2l-engine-recall.html#post1608776331
• Manufacturing Window: The L87 recall is tied to a specific production period (March 1, 2021–May 31, 2024) with defective components from suppliers. The LT2, produced for the lower-volume Corvette, likely used different batches or suppliers, or benefited from stricter quality control. GM’s 2025 L87 engines are also exempt from the recall due to manufacturing improvements, suggesting the LT2 may have been built with similar or better processes.
• Oil Viscosity: The LT2’s use of 0W-40 oil from the factory aligns with GM’s recall remedy for the L87, indicating that higher-viscosity oil may reduce bearing wear. The L87’s initial 0W-20 specification may have exacerbated issues in defective engines.
• Application Differences: The LT2’s dry-sump system and performance-oriented design reduce stress on components during high-RPM operation, unlike the L87’s wet-sump system, which faces different load patterns in truck applications (e.g., towing).
• Production Scale: The Corvette’s lower production volume (tens of thousands vs. nearly 600,000 L87-equipped vehicles) means fewer opportunities for defective components to affect LT2 engines, and GM may prioritize quality for its flagship sports car.
Conclusion
The LT2 V8 in the 2025 Corvette differs from the L87 V8 in GM’s recalled trucks and SUVs through its performance-oriented design (dry-sump, shorter intake runners, higher horsepower), use of 0W-40 oil, and apparent exemption from the manufacturing defects affecting L87 engines from 2021–2024. The L87’s recall stems from faulty connecting rods and crankshafts, leading to engine failures, while the LT2 has no reported similar issues, likely due to different production processes or quality controls. Owners of L87-equipped vehicles should check their VIN on GM’s recall lookup website for inspection and repair details, while Corvette owners can rest assured the LT2 is unaffected by this recall."
https://www.corvetteforum.com/forum...921439-6-2l-engine-recall.html#post1608776331
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