L92 Block LS3 Block?
06-18-2008, 06:22 PM
#3
From my understanding the only difference is that the L92 has some machining in the valley for DOD/AFM provisions.
I would too be interested is what differences there are if any.
I would too be interested is what differences there are if any.
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06-19-2008, 02:52 AM
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If we are just talking about the block then the rings, pistons, compression, machining of the block are all diffrent. The heads are also diffrent no VVT, and the valves are hollowed and lightened on the LS3. But from what im reading this could just mean from 08 and forward the l92 will be machined diffrently as well.
"When the block is honed, the bottom of the honing tool needs clearance so it doesn't contact the block below the bore." Rydzewski told the Corvette Action Center. "Before the honing operation, the block is machined in that area to provide (hone over-travel) clearance. The resulting surface geometry has a big impact on the block structure. The hone over-travel clearance used to be machined with a 3-mm radius. With LS7, to get more strength in that area, we changed to a more gentle, 8-mm radius. That was a big durability enabler at the LS7's power level. When we got into the LS3 finite element analysis (FEA), we found our safety factor needed some improvement, so we applied what we learned about LS7's hone over-travel cut-out. We were able to increase the radius to 10-mm which was worth about a 20% improvement (compared with the LS2 and '07 L92 blocks) in the strength of the block structure in that area."
Old vs. New
More cutting-edge technology is in the LS3 piston and ring package. The piston is a flattop design, cast with a hypereutectic, aluminum/silicon alloy containing traces of copper and nickel. The compression ratio, 10.7:1, is down slightly from 10.87:1 in '05-'07. This piston is the same as the L92's 10.5:1 unit except for a valve relief the truck piston has for additional piston-to-valve clearance required by the L92's variable cam phasing. When the relief is removed, 0.2 compression is gained but, to get higher than 10.7 requires a domed piston, the cost of which was deemed unnecessary considering LS3 met its performance and efficiency goals at 10.7:1.
Ring grooves are machined with a slight upward tilt which was increased by 0.25° for '08. The top ring's tilt disappears as the ring land flexes under the pressure of combustion such that sealing and oil control are optimized. The other two grooves' tilt enhances the ability of the second ring and the oil ring to scrape oil off the cylinder walls. To further improve oil control, the LS3 piston has four holes drilled in its skirt, just below the oil ring groove downwards into its interior. These holes, two adjacent to the major thrust surface and two adjacent to the minor thrust surface, improve oil drainage from below the oil ring.
And if you want some more reading: http://corvetteactioncenter.com/spec...ls3_page1.html
"When the block is honed, the bottom of the honing tool needs clearance so it doesn't contact the block below the bore." Rydzewski told the Corvette Action Center. "Before the honing operation, the block is machined in that area to provide (hone over-travel) clearance. The resulting surface geometry has a big impact on the block structure. The hone over-travel clearance used to be machined with a 3-mm radius. With LS7, to get more strength in that area, we changed to a more gentle, 8-mm radius. That was a big durability enabler at the LS7's power level. When we got into the LS3 finite element analysis (FEA), we found our safety factor needed some improvement, so we applied what we learned about LS7's hone over-travel cut-out. We were able to increase the radius to 10-mm which was worth about a 20% improvement (compared with the LS2 and '07 L92 blocks) in the strength of the block structure in that area."
Old vs. New
More cutting-edge technology is in the LS3 piston and ring package. The piston is a flattop design, cast with a hypereutectic, aluminum/silicon alloy containing traces of copper and nickel. The compression ratio, 10.7:1, is down slightly from 10.87:1 in '05-'07. This piston is the same as the L92's 10.5:1 unit except for a valve relief the truck piston has for additional piston-to-valve clearance required by the L92's variable cam phasing. When the relief is removed, 0.2 compression is gained but, to get higher than 10.7 requires a domed piston, the cost of which was deemed unnecessary considering LS3 met its performance and efficiency goals at 10.7:1.
Ring grooves are machined with a slight upward tilt which was increased by 0.25° for '08. The top ring's tilt disappears as the ring land flexes under the pressure of combustion such that sealing and oil control are optimized. The other two grooves' tilt enhances the ability of the second ring and the oil ring to scrape oil off the cylinder walls. To further improve oil control, the LS3 piston has four holes drilled in its skirt, just below the oil ring groove downwards into its interior. These holes, two adjacent to the major thrust surface and two adjacent to the minor thrust surface, improve oil drainage from below the oil ring.
And if you want some more reading: http://corvetteactioncenter.com/spec...ls3_page1.html
Last edited by onefastfox; 06-19-2008 at 03:07 AM.
06-19-2008, 08:30 AM
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Thanks for the info. I was just curious since I just bought an L92 engine and was going to use the block as a nice starting point for a good build.
