Hearing an LS Roar!

The final stages of making our GM 6.0 L V8 re-build stronger and faster!

July 29, 2022

12:00 AM

Bryan Irons

Words and Photos by Bryan Irons @bryanirons

If you’ve been following our GM 6.0 L V8 LS rebuild, you know about our specific goal of repurposing it for an old square-body pickup. We sourced this engine from a 2005 Silverado HD and was borderline junkyard fodder at the time we got our hands on it. After months of tooling and replacing vital components, our aim to make it better, stronger and faster is now becoming a reality.

In our first instalment (4WDrive Volume 24, Number 2), we inspected the engine’s internals for excessive wear and damage. Nothing we found incited concern so for the second instalment (featured in 4WDrive Volume 24, Number 3), we started reassembling the block with some upgrades and ‘while we’re at it’ parts.

This is a designated LQ9 engine and factory-rated at 345 hp with 380 ft-lbs of torque. Of course, this is not enough power that we want. After we installed a performance camshaft and associated valvetrain components, our current objective is to make sure we get it properly fed for a long bright future of trail running.

Production for an LS spans from 1997 to 2020 for the Gen 3 and Gen 4 units. As a result, there are a plethora of parts and components available. This also makes it confusing when trying to compare apples to apples in such a sea of aftermarket suppliers.

As we want the engine to have reliable power for a daily driver (that pulls double duty as a weekend trail warrior), we like parts suppliers that have been around the block for a while with an established lineage. ‘Experimental’ parts are not what we need when 150 km (93 mi) of dirt road lays between a broken-down rig and the nearest parts store. With all of our important part-purchasing decisions, you will not see any offshore components or Amazon specials in this build.

Bryan Irons

General Motors invested huge sums and untold hours into the ignition and fuel injection system of the LS platform and we wanted to salvage as much of the ‘good stuff’ as we could. We felt that an aftermarket controller system and wiring harness would be preferable over a cut-down factory harness and engine control module (ECM), given the mildly aggressive camshaft and the possibility of future modifications.

Plus, we’re not crazy about paying for an updated tune every time we make a change. So an update with self-learning capabilities would be a welcome addition.

To this end, we were comfortable with a F.A.S.T. EZ-EFI 2.0 fuel injection controller and EZ-LS ignition controller and all the associated wiring harnesses. This can all be purchased under a single part number of 30405-KIT from Summit Racing. The two separate computer systems communicate via a Can-Bus network making the addition of dash instrumentation and transmission controllers simple since the networks connect together.

Typically, separate sensors are required for each of the computer systems to measure the same parameters. Not with the F.A.S.T system. Only one touch-screen is required for entering parameters. Laptops or scheduled dates on a chassis dyno are not needed. Even the wiring harness is complete with protective wrapping and OEM-style connectors. Each wire has also been printed on for easy identification.

Falling back on our ‘parts that have been around for a while’ theme, we decided to hook up the EZ-LS ignition controller to the factory coils since they are extremely reliable and widely available. The controllers also allow the use of original sensors for gathering running information. The cam position sensor, crank position sensor, even the coolant temperature, air temperature, and manifold pressure are all ‘over the counter’ parts. No special-order components are needed.

With the spark taken care of, we now wanted the optimal amount of fuel and air. We could have stayed with the original intake manifold but ours received some damage when the engine was being removed. The drive-by-wire throttle body also needed to be changed to a drive-by-cable for the controllers.

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Tucked under the dash of our pickup are the controllers for engine management. We could’ve mounted them in the engine bay as they are fully sealed and potted, but we like keeping them away from the elements as much as we can.

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To feed the harnesses through the firewall, we used a Daystar Firewall Boot (right) wherever one was not included in the harness.

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All the wires in our harness were printed on individually. Here you can see the Cooling Fan #1 Relay switch leg.

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Where the wiring is to connect to a sensor or other device, a tag is also placed on the bundle.

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The only sensor we had to buy was an intake air temperature sensor, and it was a basic one that we found at a local shop.

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The factory oil packs and original GM wire distribution harnesses just plug in…after a good cleaning and inspection, of course.

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Our F.A.S.T, Big Mouth LT throttle body is a more cost-effective version of their billet aluminum units.

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Ours was ordered with new sensors, although we could have reused the ones on the original throttle body.

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The LSX intake manifold on our truck motor is overkill, but we love the look and it has been proven multiple times to increase horsepower.

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The 33 lbs/hr Injectors from F.A.S.T. from Summit Racing and the USCAR plug style don’t require an adapter to plug into the harness. Notice the ICT Billet adapter to get the proper length to fit our fuel rails?

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We have put enough wiring into vehicles to know that you need to take your time routing, connecting and protecting all the wiring harnesses. We ended up using a Painless Performance Power Products’ braid kit to organize the wiring that wasn’t already sheathed

Both were great excuses to step up to a slightly more performance-orientated intake manifold and throttle body to help gulp up that little bit of extra air the 6.0 L needed. A F.A.S.T. Big Mouth LT 92mm drive by cable throttle body was the perfect size for our targeted power numbers. It bolts directly to an LSX intake manifold. It also comes complete with an Idle air control valve and throttle position. We’re not building a drag car here, yet.

The final component was the actual fuel injectors and how to size them properly can be tricky. Injector sizing does have a ‘Goldilocks’ zone. An injector that is too large can have poor idling characteristics and one that is too small will not allow enough fuel when needed. Luckily, there are plenty of online calculators to figure out what will work best. However, there’s some specific information you need to calculate including:

The estimated horsepower. Be realistic.
Is it naturally aspirated or boosted? If it’s boosted, by how much?
The fuel type. E85? Gasoline? Methanol?
The fuel system operating pressure? Most injectors are rated at 43.5 Psi
How many injectors?
What is the maximum duty cycle? Typically, 80 percent injector ‘on’ time is specified to keep from burning the injectors out.

We used a few different calculators for our estimated 500 hp naturally aspirated gas-drinking engine. It had 58 Psi of fuel pressure and eight injectors to require 33 lbs/hr pieces to fuel our system.

Injectors are available with many different connector types and lengths. We ended up with a set of F.A.S.T injectors from Summit Racing that are designed to connect to our wiring harness’s USCAR-style electrical connectors. These injectors are slightly shorter than the original LS1 height injectors. So, we used a set of injector spacers from ICT Billet, which made them work perfectly with our intake manifold’s fuel rails.

We installed and wired-up all of the above-mentioned components. Now, we’re just waiting to make some final connections, install a cooling system and hear our 6.0L roar back to life. Check out what we did to get to this point.