February 2013 Chevy High Performance Q&A

Kevin McClelland Mar 6, 2013 0 Comment(s)

Unfortunately, we refer to all Gen III and Gen IV small-block engines as LS series. This is because the engines are built on the original architecture that was launched with the LS1 engine. As we’re sure you know, earlier small-blocks went by many other designators, and one of the most confusing could be the LT engine family. There was the Gen I LT-1 back in 1970, the Gen II LT1 (without dash!) that came out in 1992, and then the LS engines starting with the 5.7L LS1 in 1997. This was the birth of the LS lineage with the Gen III LS2 coming in the ’05 Corvette displacing 6.0 liters, and the current Gen IV 6.2L LS3 that was debuted in 2008. There have been many engine designators for the LS engines as the L-99, L-92, LS6, L-76, and many others.

B-Car Boogie

I want to add a six-speed manual transmission to my ’96 Impala SS. Could you guys help me find a main pedal bracket kit or give me advice on the best way to go? Thank you, and love your magazine.

Jamario Walker

Columbus, GA

Jamario, you know why GM designated the Impala a B-body? It’s because that they are big, bad, and bodacious! They didn’t come from the factory bodacious, but you can certainly make them that way.

You’re asking for one tall order since GM never offered a manual transmission option in the late B-cars. A few guys have built their own swaps, but we’ve found a company that has done all the hard work for you. Check out B-Body High Performance, which offers a complete trans swap kit that includes the clutch pedal mount for the hydraulic clutch, a clutch pedal, and a modified factory trans crossmember. These components are laser-cut and TIG-welded in fixtures for repeatability. They also include firewall reinforcement brackets to support the added load of the clutch pedal operation. Give B-Body High Performance a call for more information at (941) 6SPEED-1 or check it out online, as B-Body has a ton of photos of the components and swaps preformed by both the company and its customers. Good luck with your Imp!

Source: bigfastcar.com

Pressure Equals Work

I have been pondering this engine setup for years but I want to know if I am correct. I want to build a very high-revving engine with a turbo. It doesn’t matter if it has no low-end torque. The high revs thrill me.

If I take a large-bore block and throw in a very short-stroke crank, using long rods should give a slower piston acceleration while the wider pistons should decrease the chance of detonation because of a lower combustion chamber pressure (at normal atmospheric pressure, no boost).

It seems counterproductive when many stroke their engine to the max. Drive it like you stole it!

Todd Kibbe

Providence, RI

The bottom line is cylinder pressure is cylinder pressure. The larger the bore, the more surface area there is that the same amount of pressure has to push down against the piston crown. The motoring (no cylinder firing) cylinder pressure will be dictated by the swept volume of the cylinder and its parts. The ratio among the swept volume and the combustion chamber, combustion chamber floor (piston crown), head gasket volume, and ring land area around the piston sets the compression ratio. When you then add fuel, air, and spark, you increase the cylinder pressure by extracting heat from the fuel and expanding the air. If you have 1,000 psi of cylinder pressure on a your large-bore/short-stroke combination, versus a small-bore/long-stroke combination, displacing the same cubic inch you still have 1,000 psi in the combustion space. The power will be close in both combinations except for the frictional differences. You could build your combination for your high-revving thrills, but don’t look for reduced detonation threshold from your large bore exercise.

Now for your “counterproductive” statement about stroking your engine. Yes, there is a feasible displacement limit for any engine design. Increasing the displacement on a boosted engine is a great way to make outrageous power. Remember, every time you double atmospheric pressure going into the engine you basically double the output of the engine in a boosted application. Of course, you must control charge temperature, and don’t overstress components to failure. In other words, if you push 14.696 psi of boost into your engine you should expect close to a 100 percent increase in power. This is with a turbo compressor arrangement. With a supercharger you must drive the compressor with power from the engine. It’s going to steal some of your gains.

Let’s just say for numbers you build a 302-cid small-block. At 1.5 hp per cube it will produce 453 hp, naturally aspirated. If you stuff 14.7 psi of boost down its throat, with the proper configuration, you could expect around 800 hp! If you build a 377 small-block with the 4.155-inch bore and 3.48-inch stroke at 1.5 hp/cube that equals 565 hp. Now throw the same one atmosphere at it and you will yield 1,018 hp!

This is a very simplified example of the power potential of boosting an engine. We’ll take the displacement every time if you have the package to control the power. Great questions, and keep on thinking!

Multi-Coil Benefits

I read several magazines every month, but I enjoy your technical question section the most out of any of these. I really have no personal project that caused me to raise this question, just the thoughts that came from all my sources.

I was under the impression that one of the benefits of the LS engine was the individual coil pack for each plug. I have read how having such a setup allows the coil to have longer to recover between fires, which sounds very logical and as a great gain. However, I see some building very aggressive LS motors, but using a Ford distributor and returning the engine back to a single-coil configuration. I was hoping you could shed some light on why this is being done to what I thought was a superior design. Thanks.

Randy Ranloachi

Via email

You’re spot on with your assessment of the multi-coil features and bennies. The coil-near-plug arrangement gives the coils 610-plus degrees of crankshaft rotation to saturate with a fresh 12V charge to be ready for its next high-voltage discharge. It also eliminates the issues with secondary voltage across the distributor cap, rotors, and the long plug wires that have a bad tendency to leak voltage when the load goes up. Electricity will take the easiest path of flow, and if it’s easier to flash voltage over the plug insulator, or around a boot to a header when the cylinder pressure gets high, it will. Also, with individual coils for each cylinder you can control the spark advance to each cylinder. When the detonation sensors see spark knock, they identify which cylinder is having the issue by using the crank position sensor and the cam sensor and pulls out the spark to that individual cylinder until the cylinder has recovered.

Now, back to the engines you’ve seen that have reverted back to a distributor and single coil. Chevrolet Performance designed a front cover assembly to run a standard distributor and mechanical fuel pump for limited stock car application. To this day, some sanctioning bodies are scared of electronics and their inability to police what the competitors are doing with them. The way GM got around this was to create the ability to run a distributor for the carbureted LS engines. Its LS front distributor drive cover is sold under PN 88958679. Using this front cover requires the use of a small-block Ford-style distributor, mechanical fuel pump, special water pump, accessory drive, and damper.

To retain the eight ignition coils on carbureted applications, you can also run an MSD 6LS-2 Ignition Controller for carbureted LS engines. MSD offers two different controllers based on if you have a 58X or 24X crankshaft reluctor ring. These systems are very cool as you can use pre-programmed ignition curves that can be changed by swapping out timing modules, or you can create and download your own custom ignition curve based on your application. The software is supplied with the ignition controller as part of the package.

Thanks for the question; surely you’re not the only one who has noticed a distributor on LS engines. Unless it’s needed to meet some rules requirements, or you’re completely put off by electronics, we would retain all those lovely coils on the valve covers.

Sources: gmperformanceparts.com, msdignition.com

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