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Tuning An LS2 Engine - Cubic TwistWe Poke and Stroke an LS2 to 454 From the May, 2011 issue of Chevy High Performance By Steven Rupp Photography by Steven Rupp
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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 This is the phosphate-coated... This is the phosphate-coated LS MID sleeve kit from Darton. While eight sleeves are needed there are actually three part numbers here: the four in the center, cylinders one and eight, and cylinder numbers two and seven. The sleeves for LS1 (Gen III) come in two bore size ranges. The smaller set covers from 4.125 to 4.160 inches while the larger 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. 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.  Getting the magical 454 displacement...  Getting the magical 454 displacement number is all about bore and stroke. To address the former, Turn Key Engine Supply honed out our Darton sleeved block to 4.185 inches. We could have gone as big as 4.200 inches, but we like the idea of having a little extra meat left on the sleeves.  The heart of any stroker is...  The heart of any stroker is the crank. For this build we decided to try one from K1 Technologies. Their line of 4340 steel LS cranks features a nitride coating for improved bearing life and won’t break the bank in terms of cost. This one (PN 346-4125RB6F) set us back just under $800.  We also picked up a set of...  We also picked up a set of K1’s connecting rods. The 6.125-inch billet 4340 steel H-beam rods came in a weight match (+/- 1 gram) set. They were shot-peened and we ordered them with ARP 2000 fasteners. The street price on the set (PN CH6125ALLB-LS8) was just over $500 with the ARP bolt upgrade.  Here’s Wiseco’s 2618-alloy...  Here’s Wiseco’s 2618-alloy forged LS piston. The 2618 alloy is stronger than 4032, but typically wears quicker. To remedy this, Wiseco uses a permanent skirt coating that lasts the life of the piston. Forged pistons have a reputation for being noisy, so Wiseco offsets the pins like the OE to reduce noise on startup. The low-friction ring package is designed to maximize ring land thickness and utilizes a special oil ring design to reduce consumption.  The first step in the assembly...  The first step in the assembly process was getting all of the rods mated with the pistons. Organization was paramount since the pistons needed to be orientated in the proper direction. We also file-fit all the rings and gave everything a liberal coating of Royal Purple assembly lube.  The goal with this engine...  The goal with this engine is to retain great street manners. Sure, we could have tossed in some crazy-big stick to nail down a bigger dyno number, but we wanted an engine that would be easy to live with on the street. What we chose was a COMP custom grind with 243/259 duration at 0.050 with 0.624-inch lift on a 114 LSA. This would be a big cam in a normal LS engine, but with our large displacement it falls in the middle of the bell curve.  We then set our K1 crank in...  We then set our K1 crank in place. To secure the mains we ran a stud kit from ARP (PN 234-4317, $295). Again, we were generous with the assembly lube.  Then it was time for the fun...  Then it was time for the fun part: installing the pistons and rods. This task was made easier with the use of a 4.185-inch ring compressor installation sleeve from Wiseco.  With the pistons installed...  With the pistons installed we were able to spin the assembly and get an idea how much of our piston skirts would be poking out at bottom dead center. As you can see the piston does protrude a bit, but it’s not a lot considering the 4.125-inch stroke. Wiseco designed these slugs to resist rocking at BDC, and the extra length of the Darton sleeves helps as well. We found an old LS2 block with scored cylinders, but Demirjian says various LS blocks would be suitable candidates. As he explained, "I like the LS1 block because it has solid main webs with no cast-in breather holes. I will install the large bore, 4.200-inch sleeves in the LS1 blocks but not the LS6. The LS6 blocks have the cast-in breather holes making them too weak, in my opinion, to bore out for the larger bore sleeves. Now the Gen IV blocks also have breather holes but on these blocks the floor of the coolant section has been raised leaving more material for the sleeves to sit on, resulting in less chance of cracks developing compared to the LS6 block." The process of installing sleeves is an exercise in supertight tolerances. Bore centers must be held to within +/- 0.0005 inch. The bores themselves, for sleeve fitment, must be held to +/- 0.00025 inch, or a quarter of a thousandth of an inch! This is why having the right tools and skills are imperative.Demirjian has had blocks come in from various shops doing the installs dry that were six thousandths out of spec. In these cases the block couldn’t be saved and the only option was to pull the sleeves and install them in a correctly machined block. If all of this sounds labor intensive, that’s only because it is. The basic charge to machine, stress relieve, install the sleeves, and deck the block is $1,175. Add in $100 to bore the block to within honing range and another $75 if you want the notches cut for rod clearance. The sleeves retail right around $1,300 and when you add it all up, you’re at $2,650 for parts and labor. Of course, you have to factor in the cost of the block, but good used donors can be found for around $400 (give or take). That means the total for a big-bore aluminum small-block would be a hair over $3,000. Not cheap, but very competitive to the aftermarket LS blocks that are currently available.  With the rotating assemble...  With the rotating assemble installed we went ahead and installed our sprockets and timing chain using some ARP fasteners. For this application we’re running a 24x reluctor wheel along with a 1x cam sprocket. Before building any LS engine you need to decide which electronics you’ll be using so you have the correct internal parts.  This engine will eventually...  This engine will eventually find a home in an early Chevy and to clear the frame we wanted a pan with ample clearance. This pan from Canton (PN 13-270A, $540) was the only one we found that would work in place of the F-body (’98-plus) pan commonly used in LS swaps. It has a 6.5-quart capacity and features a fully fabricated and baffled aluminum construction. As a bonus, it uses the OEM windage tray (GM PN 12558253) and F-body pickup (GM PN 12558251). To make sure everything cleared we bolted on the pan with a GM gasket and spun the rotating assembly.  What we found was that the...  What we found was that the farthest forward pair of rod bolts just barely touched the pan. To remedy this problem we marked the bolts, removed them, and then knocked off the edges with a grinding wheel. We also spaced the windage tray away from the crank with three washers at each attachment point.  We decided to run a factory...  We decided to run a factory GM pan on the dyno to save us the hassle of running remote oil lines for the Canton pan. After the dyno the trapdoor-baffled Canton pan will go back on.  Before setting the heads in...  Before setting the heads in place we installed our COMP High Energy lifters (850-16, $210) using GM plastic lifter trays.  Like a stereo system needs...  Like a stereo system needs good speakers to perform, a short-block needs to be topped off with a set of killer heads. For this build we went with a set of some of the best cathedral ports on the market, Trick Flow GenX Street/Strip 235 cylinder heads. The big 235cc intake ports should feed our 454 plenty of atmosphere and they are designed for large-bore (4.125 inches and up) LS engines. The 70cc combustion chambers are CNC-profiled so that intake valves are unshrouded. This equates to more airflow and better combustion. At 0.600 of valve lift these flow 340 cfm on the intake side and 270 cfm on the exhaust side. They came assembled and ready to bolt in place with stainless 2.08-inch intake and 1.60-inch exhaust valves.  We then installed the heads...  We then installed the heads using off-the-shelf GM head gaskets (PN 12582179) and ARP head studs (PN 234-4317). The GM MLS gaskets will have a compressed height of 0.051 inch.  To complete our valvetrain,...  To complete our valvetrain, we went with a set of COMP Ultra Gold aluminum rocker arms (PN 19024-16, $460). These CNC machined rockers are some the of best COMP offers and won’t fail when pushed hard. For pushrods we ran COMP Hi-Techs (PN 7956, $135) with a length of 7.450 inches.  To top off our long-block...  To top off our long-block we chose a 102mm intake from FAST (PN 146302, $950). This should be able to easily feed our 454 LS enough air. Its polymer construction equates to lightweight and improved heat dissipation. It’s also modular, which makes port matching it a snap if you’re so inclined.  FAST recommended these 42-lb/hr...  FAST recommended these 42-lb/hr injectors (PN 304208, $650). The design helps with idle quality and their precision-ground pintle and wide spray angle equates to better fuel atomization.  With the engine built we hauled...  With the engine built we hauled it over to Westech Performance for a little dyno time on their SuperFlow 902. For the pulls we bolted on a FAST 102mm throttle body, an ATI super damper, and a Meziere electric water pump.  We throttled up the 454 and...  We throttled up the 454 and were rewarded with a best pull of 650 hp at 6,200 rpm and 612 lb-ft of torque at 4,600 rpm on 91 octane. The torque output was great across the entire powerband with 540 pounds at 3,500 rpm and 516 pounds 6,500 rpm. Torque like that is what makes a street car fun to blast around town.  The nice thing about doing...  The nice thing about doing sleeves is that you don’t need to start out with a new block. In this case we found a used LS2 block that had a couple of scared sleeves. Just make sure the block doesn’t have any cracks or other damage. This one set us back $400, which was almost $1,000 cheaper than new from GM.  The first pass of the mill...  The first pass of the mill cut out the GM iron cylinder liners. Steve Demirjian of Race Engine Development says, “All machining must be done on a flood coolant machine or else the heat buildup during machining will distort and expand the block. This will make the tolerances impossible to hold and put stress into the block, causing it to distort even further when the engine is started.”  After this pass we were left...  After this pass we were left with aluminum bores. “On the smaller bore Gen III and Gen IV LS2 blocks, I cut a honing clearance bore slightly larger than 4.200 inches to just above the main webbing. That leaves sufficient clearance to enable honing of the blocks to 4.200 inches if desired, without crashing the honing stones into the block,” Demirjian says.  After changing cutting heads,...  After changing cutting heads, Demirjian then removed the rest of the cylinder wall material. Even though a lot of material is removed, the new sleeves are heavier and an MID-sleeved block will end up around 6 pounds heavier than a factory block. As you can see, quite a bit of material is removed in this process. It’s easy to see how someone inexperienced with this process could end up ruining a block. Demirjian then put the block on a stress relief table for an hour, a step that he feels is critical to ending up with a reliable finished product.  The block was then set up...  The block was then set up on the CNC for final processing. From there, the sleeves are numbered and the block is machined per sleeve for correct fitment. The sleeves will vary slightly in diameter, so measuring the sleeves prior to doing the finish bore work is critical.  With the machining complete,...  With the machining complete, the block was deburred, washed, and blown dry. Before dropping in the sleeves, Demirjian gave the lower cylinders a light coat of Molykote O-ring lubricant. He also installed the three small O-rings onto a lower section of each sleeve and applied more Molykote O-ring lube. The O-rings are there to keep coolant from leaking into the crankcase, the same method used in wet-sleeve diesel engines. Loctite 515 flange sealant was applied to both prevent leaks and hold the sleeves in place during decking and boring. With that finished, the sleeves could then be slid into the machined block. The sleeves are significantly stronger than the original block bores and are constructed out of the same material used in Darton’s Top Fuel and Funny Car applications.  Demirjian then used a mallet...  Demirjian then used a mallet to carefully seat the sleeves into the block. He also gave us some advice on installing the heads. He says, “If using other than factory torque to yield head fasteners, the fasteners must be retorqued after the first heat-up cooldown cycle prior to dyno runs. Failure to do this will most certainly result in a blown head gasket.” Also, keep in mind that MID-specific Cometic head gaskets, available from Darton, must be used. The sleeves were then secured in place and allowed to set up overnight. Note: The Loctite is there just to seal, and not hold, the sleeves in place; that’s eventually done by the heads being bolted on. Sleeved blocks must never be cleaned in a jet wash without honing plates attached or the sleeves will be lifted out of position due to block expansion and will not reseat themselves. This is true even for aftermarket aluminum blocks. The best idea is to stick with hand-washing with warm soap and water.  The following day Demirjian...  The following day Demirjian stress relieved the block for another half hour before beginning to deck the block. The final deck height ended up coming in at 9.235 inches. He was then able to bore the block to within honing range. With this sleeve kit, we could have gone as large as 4.200 inches for the finished bore, but we went for a final bore of 4.185 inches. Combine that with a 4.125-inch stroker crank and the result is an all-aluminum 454 small-block. What’s not to love about that much displacement in such a compact, lightweight package? CHP
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