The great thing about big-block Chevy engines is they offer gobs of luscious torque-producing displacement. The downside is that they are big and heavy, which has resulted in a trade-off between weight and displacement. These days, however, there are ways to have your proverbial cake and eat it, too.
The problem with going bigger, especially with today’s aluminum GM blocks, is that the factory steel sleeves can only be bored so far before getting too thin to be reliable. The solution is to knock out the factory sleeves and insert aftermarket sleeves that are able to go big, real big. Having the ability to go with a bore size up to 4.200 inches is a key part of getting big-block displacement from the LS2. The other half of the displacement equation, stroke, is addressed with the use of a longer stroke crank. These are readily available and a 4.125-inch stroke can be accommodated inside the typical GM LS block with a bit of finesse. The upshot of this is it’s now fairly easy to create a lightweight aluminum LS engine in the 454ci range.
This bump in available displacement equates to torque and as we all know torque, not horsepower, is the real star of the show. In addition, those extra cubes allow the use of a larger camshaft that would prove to be too raucous in an engine of more diminutive displacement.
For this build we decided to use a set of Darton MID sleeves to punch out the bore of a used LS block. The recipe also included a 4.125-inch K1 crank with standard length 6.125-inch K1 rods. When it came to selecting the camshaft we resisted the urge to slide in something too rowdy just to nail a sexy dyno figure. Instead, we chose a stick that would make great power and still offer excellent street manners. After getting our donor block resleeved by Steve Demirjian, of Race Engine Development, we headed over to Turn Key Engine Supply to complete the big-inch mill.
It’s bigger on the inside
Sleeving an LS block involves very specialized, and expensive, equipment, but more importantly it requires someone with the skill and experience to pull off the surgery. That’s where Steve Demirjian of Race Engine Development comes in. He’s been in the racing engine business since 1972 and that equates to a lot of knowledge of what works and what doesn’t. In regards to sleeves he’s been working with Darton for quite some time and is even one of the patent holders for their Modular Integrated Deck (MID) sleeve system. The MID system was developed by Darton to address the factory block’s cylinder stability design weakness due to the poor support at the upper deck area. GM’s "cast-in sleeves" make the factory engines affordable and they are great to a certain power level, but lacking when it comes to high power, boosted, or, as in our case, larger bore sizes. When the Darton sleeves are siamesed and nested, they create a solid deck of sleeve flanges held in tension, this reinforces the upper deck area and provides for individual replacement with what Darton calls MID. Unlike factory sleeves, water flows all the way around the cylinders and this promotes cooling and helps control detonation.