Darton Engine Sleeves - Block Party
How To Get Big-Block Displacement In A Small-Block Package
From the March, 2011 issue of Camaro Performers
By Steven Rupp
Photography by Steven Rupp
This is how Darton receives...
This is how Darton receives the ductile iron sleeves from the foundry. At this point it can become any number of sleeves from LS applications, to sleeves for Pro Stock and Funny Car engines. The sleeve's job is to control wear, heat, provide a platform for lubricity, and contain the combustion process without distortion. Cast iron is typically very inexpensive, breaks in well, and is brittle. The opposite of ductile iron, which is more expensive, very strong, has high elongation (meaning flexibility without breaking), and high surface hardness. Ductile is composed of a nodular structure as opposed to cast iron, which has a more graphite-flake structure.
The old saying, "There's no replacement for displacement," is dead-on accurate. Sure, you can stuff a big, nasty camshaft into a smaller engine, or spin that same engine into the rpm stratosphere and make more power, but extra cubes yields something that real performance junkies find more beneficial: torque. When it comes to going fast, torque is king and it's one reason why old-school big-block Chevy engines still command respect. Of course, the down side to all that big-block goodness is weight. It's a give-and-take deal; at least it used to be. Today it's possible to get crazy displacement even in the diminutive small-block package. For example, GM's line of lightweight aluminum LS engines started out at around 350 cubic inches. As time passed, that displacement steadily grew to 364, 376, and eventually topped out at 427 glorious inches in the LS7. But the power-mad masses clamored for more. The problem was that the iron-sleeved aluminum blocks could only be punched out so far before getting dangerously thin in the cylinder wall department. Of course there was the stroke side of the displacement calculation, but the factory sleeves were only so long. The solution turned out to be ditching the GM sleeves and going aftermarket.
Now, this isn't something you're going to be able to do yourself using common hand tools in your garage. It 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. In other words, he was the perfect guy to help us up the displacement of our LS engine. The MID system was developed by Darton to address the factory blocks design weakness of cylinder stability due to the poor support at the upper deck area. GM's "cast in sleeves" makes 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 Modular Integrated Deck (MID). Also, this design enhances water flow from block to head and promotes stability of cooling since all the sleeves are of the "wet" design. Unlike factory sleeves, water flows all the way around the cylinders, which promotes cooling and helps control detonation. You can find more tasty tidbits about Darton's MID sleeves by hitting up their website.
The ductile iron sleeve is...
The ductile iron sleeve is then machined and phosphate coated to protect against rust and corrosion. At this point all of the LS sleeves are the same.
The result is this LS sleeve...
The result is this LS sleeve kit. While there are eight sleeves, there are actually three part numbers here. The four in the center, cylinder one and eight, and cylinders number two and seven.
The coated sleeves are placed...
The coated sleeves are placed into the CNC mill for all the detail cutting and drilling. The sleeves for LS1 engines (Gen III) come in two bore size ranges. The smaller set covers from 4.125 to 4.160 inches, while the lager goes from 4.170 to 4.200 inches. For the Gen IV blocks, there's just one part number that covers from 4.125 to 4.200 inches.
For this install, we found...
For this install, we found a used LS2 block that had a couple of gouged factory sleeves. We made sure that block didn't have any cracks or other damage. This one set us back $400, which is almost $1000 cheaper than new from GM. Used LS1 blocks can be found for even cheaper.
After changing cutting heads,...
After changing cutting heads, Steve then removed the rest of the cylinder material. Even though a lot of material is removed, the new sleeves are thicker and an MID-sleeved block will end up about six pounds heavier than a stock LS block.
The block is then set up on...
The block is then set up on the CNC for final machining for fitment of the sleeves. The sleeve diameters are measured for size with a micrometer then numbered and the block is machined per sleeve for correct fitment. The sleeves will vary slightly in diameter so one must measure the sleeves prior to doing the finish bore work in the block.