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Madison Co. Virginia | GM has announced a gen6 small-block, and supposedly it's going to be built in only two sizes; 5.7L and 6.6L. That's odd, considering that GM has had a tradition of building three sizes with two blocks and two cranks for the past several decades.
GM changed so little about the basic block design from gen4 to gen5, that I rather doubt they'll change much either going up to gen-6. My guess is that gen6 will be a relatively 'soft' upgrade, similar to what we saw from gen3 to gen4 LS engines; new sensors, additional gizmos, a revamped management system; but the same basic long-block underneath, and with a lot of parts commonality with the previous generation of engines.
It's pretty safe to say that the new 6.6L will be using the same basic dimensions of the current 6.6L. But I'm puzzling over the 5.7L. Sharing the block with the 6.6L seems more likely than sharing the crank, but it will mean they'd be going to a different stroke length from anything they've used so far. *
I think a v10 version of the 6.6L would be a perfect diesel alternative in the heavy duty pickups. It would displace about exactly what the old 8.1L big-block did in the early 2000s, would use all their existing architecture, and could have HP and torque figures in the 600 range.
* Edit: To get a 5.7L out of the existing 6.6L block would require a 85mm stroke. That's within spitting distance of the 83mm stroke on the gen3 and gen4 4.8L engines. If GM does build it with those dimensions, that's going to be a high-revving easy-breathing engine, with those large valves and minimal reciprocating mass.
Edited by kipps 3/12/2026 13:29
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Chevrolet/GMC 6.6 gas vs diesel
