Tuning An LS2 Engine - Cubic Twist

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 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 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 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 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 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, 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 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, 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 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 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