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06-07 have powdered metal forged rods instead of the 08 which has powdered metal cast rods like the l61. Pistons from 06-08 should be the same.
Can confirm, 2008+ has sintered powder metal rods, one is currently bent at my desk. Pre '08 has forged rods.
Forged rods are not made from powder metal, rather for a billet stock of material; think bar stock of whatever species of steel they are using.
Powder metal is literally metal powder of whatever species is specified that is poured into a die and pressed together. When removed from the die the "green" part is then baked in a high temperature oven for several hours.
For note; forged rods will always have a forge line on them, its a 1/16 - 3/16" line that runs around the middle perimeter of the rod, powder metal rods will not. Forged rods have much better grain structures than powder metal and since they are formed from a bar stock, less porosity when compared to powder metal.
Is there any consensus to the 08 pistons? Are they weak? Does the ring end gap on a rebuild need to be opened (I am believing this more than anything else at this point) Seeing many broken pistons at this exact same point, it seems to be the weakest area. Even the manufacturers vary how much the leave hanging by the valve relief.
During that drive I was logging and there was no knock and PE was 11.5-11.8 so I don't want to start blaming that since it has been dialed in for a couple months that way.
Nope... I'll bet there are many Cobalts running around like this where the plug was missed.
I am running it just as hard as before if not worse now that I have another engine sitting here.
For note; forged rods will always have a forge line on them, its a 1/16 - 3/16" line that runs around the middle perimeter of the rod, powder metal rods will not. Forged rods have much better grain structures than powder metal and since they are formed from a bar stock, less porosity when compared to powder metal.
One of us may be backwards here, but my understanding is forgings typically have a wider flashing line then cast. Where forged rods clearly have grinding marks from the cleanup process.
See this rod is forged, with a wide line. I would say more on the lines of 3/16-1/2" for forge lines. Does this make sense?
Where a cast steel rod line is barely perceptable in this image:
One of us may be backwards here, but my understanding is forgings typically have a wider flashing line then cast. Where forged rods clearly have grinding marks from the cleanup process.
See this rod is forged, with a wide line. I would say more on the lines of 3/16-1/2" for forge lines. Does this make sense?
Where a cast steel rod line is barely perceptable in this image:
It really depends on how they are forged and cast. The guy you were quoting was comparing forged to powdered metal sintered. If you are just sintering, then you wouldn't have a line, but I believe the sintered rods are also forged. There may be a small line depending on how they forge it.
The 2 processes are extremely different and the cleaning process after casting during machining can remove the casting lines. Here's a rod being forged.
With all metallurgy, length and finish equal, I's are lighter where H's are stiffer and stronger and more applicable in high torque, High HP apps. I's with everything equal are better for high RPM builds due to their lighter construction. Best of both worlds, H Titanium rods if you have deep pockets.
Nein. I-beam configuration will always be stiffer in bending for the same weight than H-beam. That's just how it is. Axially if they are the same weight then they are equal in stiffness. If an H-beam is stiffer than I-beam then it weighs more, and you could have made a stiffer I-beam.
Nein. I-beam configuration will always be stiffer in bending for the same weight than H-beam. That's just how it is. Axially if they are the same weight then they are equal in stiffness. If an H-beam is stiffer than I-beam then it weighs more, and you could have made a stiffer I-beam.
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07-21-2017, 01:59 PM
