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1968 Chevy Camaro Engine Upgrade - Strategic StrokeWe Punch Up The Displacement Of Our LS2 To 402 CI And Hit The Dyno From the February, 2009 issue of Camaro Performers
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The biggest part of any engine...
The biggest part of any engine build is the block. In our case it’s this GM Gen IV 6-liter LS2 block. We could have used the block from the old engine, but that would have meant taking the car off the street. To save time we picked up this brand new one from a buddy for $1,000. If you’re looking for a block, shop around because the deals are out there. Keep in mind that while the blocks from GM do include things like cam bearings and main bolts, they come with almost nothing else; such as sensors and LS-specific plugs.
There’s no replacement for displacement. It’s an adage as old as hot-rodding and one of the set-in-stone truisms. It’s also the thought process behind the ever-increasing popularity of stroker engines. Back in the day, the most popular combo was turning a common 350 small-block into a 383. But today just about any mill can get the stroker treatment. The real gain of any increase in displacement is torque. It’s why a big-block almost always beats a small-block in this department.
If you’re building an engine, and you need to buy a rotating assembly, then going with a stroker makes even more sense because the cost of a stroker crank and rods is only a little more than the stock-sized stuff. For example, Lunati sells their 355ci Sledgehammer rotating assembly for $2,362. But their 383 kit is only $2,404. That’s 28 additional power-producing cubes for a paltry 42 bucks. No other speed part gives you such a return on your performance dollar than a stroker. Well, maybe nitrous, but that’s another story for another time.
Like all good things, you can take the theory too far. Go too big on the bore and you can weaken the cylinder walls to the point of failure. You can also run in to overheating problems. Push the length of the stroke to the ragged edge and you could experience another set of failures: the biggest problem can occur when the piston reaches the bottom of its stroke; this is known as bottom-dead-center (BDC). If too much of the piston extends out of the bottom of the cylinder bore, and the piston isn’t designed for this, the piston can rock, scoring the cylinder walls thus eventually junking up the engine. That’s why it’s always good to check with the manufacturer on what they recommend. We also think a good way to go is with a stroker kit. In a kit the parts are designed to work together in a particular application rather than hobbled together in the hopes they are mechanically compatible.
Lunati and Wiseco have been working together to make sure the stroker kits they offer work. And more importantly, are reliable. The pistons in their LS stroker kits are specifically designed for LS applications. This is critical since every detail matters when you’re pushing the stroke to the ragged edge of what’s possible with a stock-sleeved cylinder.
We’ve been itching to put a bit more power under the hood of our ’68 Camaro, Bad Penny. The LS2 currently in it is running the stock GM short block with a medium-sized COMP cam, FAST 90mm intake, and some sweet AFR 205 heads. It made good power, but for how we use the car, more low and midrange torque would make it quicker—hence more fun.
 “Like all good things, you...  “Like all good things, you can take the theory too far. Go too big on the bore and you can weaken the cylinder walls to the point
of failure.”
 The main part of a stroker...  The main part of a stroker kit is the crank (part #J0711ER), and this one is a beauty. This four-inch-stroke Lunati Pro Series forged crank is their top-of-the-line unit. Made from the best quality 4340 steel, this piece is American forged and machined. The shaft surface finish is grade 5 RMS or better, and the journal radii are ground to .140 inch. In addition, each rod journal is drilled with a 7/8-inch or 3/4-inch lightening hole to reduce inertia weight. To ensure everything was just right Outlaw Racing line-honed the block specifically for this crank.
 Working with the crank to...  Working with the crank to get us the right stroke are these 6.125-inch Lunati H-beam rods (part #6125H). The rods are forged from the same aircraft-grade 4340 steel as the crank. Then they are heat treated, stress relieved, shot peened, and magnafluxed to ensure they will last. After all, connecting rods are subjected to some of the highest stress levels of any bottom-end engine component. When the piston direction reverses from top dead center, the forces on the rod can exceed 12,000 pounds. To hold up to the punishment the rods also utilize ARP cap hardware.
 Here’s Wiseco’s new 2618-alloy...  Here’s Wiseco’s new 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 O.E. to reduce this noise on startup. A low-friction ring package is designed to maximize ring land thickness and utilizes a special oil ring design to reduce oil consumption. Because the pistons swing very close to the reluctor ring on LS engines, Wiseco was the first to design a forging around a 2.250-inch wristpin length. To make this possible, it was designed with just enough pin boss spacing to fit the factory connecting rod width. This further increases pin bore bearing area and had the added benefit of reducing pin flex. This piston uses the Wiseco Flow-dome technology to hit the needed compression ratio target: In our case, 11.1:1 by keeping the piston at only -3cc, even with the valve reliefs.
 The stroker kit came from...  The stroker kit came from Lunati fully balanced, but since we switched to Wiseco’s new Flow-dome pistons, we needed to match everything up again. Thankfully, Andy at Outlaw Racing, was more than equipped to perfectly balance all of our parts together.
 In many cases part of the...  In many cases part of the gain from doing a stroker kit is in the area of increasing the bore size. On an iron block it’s easy to go .30-inch, .60-inch, or even more over stock with no ill effects. With an LS engine it’s not that easy. The aluminum blocks have steel sleeves that aren’t terribly thick. You could go .30-inch over, making a 408, but the risk far exceeds the gain. If you want to go bigger than a 402, then look into having the block re-sleeved, or if weight isn’t an issue, look into one of GMs iron 6-liter blocks. Outlaw Racing bolted on the torque plate and honed our cylinders out to 4.005-inch. This was just enough to clean up the cylinder walls, and our sleeves are still thick enough to handle the abuse we plan on putting them through.
 Andy also likes to hone each...  Andy also likes to hone each rod end for its individual pin. He’s looking for the pin to freely slide through the rod and not bind or hang up in any way.
When it comes time to mate... 
When it comes time to mate the pistons to the rods, organization is the key. Andy lined all the pistons up in the correct orientation and started the somewhat tedious task of installing the spiral locks. As usual, we made sure to coat everything in Torco assembly lube.
 Andy prefers to test-install...  Andy prefers to test-install the cam before setting the crank in place. This way, if there’s any issues with the cam bearings it can be easily addressed. All new GM blocks come with the cam bearings pre-installed, so that’s one step we get to skip. We want our Camaro to have the same great street manners it had before, so we only bumped up one size in the COMP catalog. The old one was a 232/234 at 112, and the new one is a 238/240 with the same 112 LSA. With the extra 38 cubes, the change in idle characteristics should hardly be noticed.
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