While it’s no surprise than GM’s latest and greatest generation of small-block V8 engines enjoy improvements over the their Gen-III and Gen-IV LS predecessors, the level of strength enjoyed right off of the assembly line by the Gen-V LT1 and LT4 engines did catch some people off-guard.
While both engine blocks are aluminum, and share a number of design features between them, there are also some key design differences which give the Gen-V engines an advantage when it comes to strengths of the OEM shortblock. Bryan Neelen, owner of Late Model Engines, goes over those similarities and differences.
“Some of the features the two architectures share are the head bolt pattern, the lifter layout, deck height, and bore-spacing. Both engine families have a 9.240-inch deck height, and a 4.400-inch bore-space.,” Neelan explains of the LS and LT short-blocks. “Beyond that, there’s not much else that is compatible between the LS and LT.”
Strengthening The Deck
Unfortunately for LT enthusiasts, you aren’t able to take advantage of all of the accessories available for the LS. “The front and rear covers, valley pans, and oil pans are all different on the LT,” Neelen explains. “Even the water pump layout is different.” However, this is EngineLabs, and we care more about power than accessory compatibility, especially since those accessories don’t affect the strength of the engine, directly or indirectly.
“GM has incorporated some of the race technology and what was learned from the Chevrolet Performance LSX block into the LT production block.” Neelen says. “Specifically, we’re talking about the deck surface area. All the previous generations of LS had an open water jacket design, whereas the LT has the new gusseted deck surface.”
The aftermarket has long known that closed and semi-closed decks offer more dimensional stability in an engine block, but it’s definitely nice to see manufacturers taking notice. “The new deck design not only increases the structural integrity of the deck surface itself, but also the cylinder walls,” confirms Neelan.
“Typically you’re going to see engines [with open decks] that will shadow the bores or deform adjacent to the bolt holes, and that’s exactly where GM put the strengthing gussets in the LT blocks. That alone is a huge improvement over the [factory] LS, and speaks volumes to the quality of the LT blocks.”
[Fastener] Size Matters
Another area where the General beefed things up is in the hardware used to hold the cylinder head onto the block. “Stepping up to 12mm bolts from the 11mm head bold diameter has been huge,” says Neelen. “Also, they reinforced the clamping area of the cylinder head itself, adding structural integrity. By adding column height in the cylinder head, along with the increased diameter of the bolt holes and adding the gussets to the water jackets, the LT platform can handle significantly higher cylinder pressures than the LS.”
By now, you’re probably asking exactly how much more power can the LT aluminum blocks hold over the LS versions. “We were borderline at 1,000-1,200 horsepower with the LS block. You couldn’t really confidently enter that realm with the LS block, with only four bolts per cylinder,” reveals Neelen. “With the LT engine, we’re seeing engines living at 1,400 to 1,500 rear-wheel horsepower with a production block. It’s still a four-bolt design, but will the deck, bolt-diameter, and cylinder head integrity improvements, it results in a much higher strength package.”
So while Neelen’s current limit of 1,500 horsepower is impressive, he’s not calling that the definitive line in the sand. “We’re definitely looking forward to the future and seeing how far we can push this platform.”