4 on the Floor: LQ 6.0L Upgrades

The right mods to your LQ4 6.0L can produce a truckload of power.

The right mods to your LQ4 6.0L can produce a truckload of power.

Words and Photos By Richard Holdener

When it comes to affordable truck motors, or, for that matter, LS performance in general, bigger really is better. Scour the wrecking yards for affordable, iron-block LS engines and likely as not, you will find plenty of 4.8L and 5.3L variants (the most common being the LR4 and LM7). Unfortunately, the larger LQ4 6.0L versions will be few and far between. Don’t get us wrong, the smaller 4.8L and 5.3L motors are awesome in every way, and can be made to produce sick power when properly motivated. It’s just that everything the smaller motors do, the larger 6.0L does even better.

In addition to displacement, the 6.0L was also blessed with improved cylinder head flow. Despite an increase in chamber size, the factory 317 heads flow better than the smaller 706 (and comparable) heads usually found on the 4.8L/5.3L twins. Run in a similar fashion on the engine dyno, a stock 6.0L will produce a solid 70 hp more than a 4.8L (404 vs 335 hp in our last test), and 45-50 hp more than the 5.3L (404 vs 352 hp in our last test), with similar torque gains through the entire curve.

Okay, we’ve convinced you to step up to the larger 6.0L (it will be more expensive than the 5.3L or 4.8L), but what can be done to make a good thing even better? To illustrate a few of the many possibilities, we decided to cover a build up of a typical street-oriented 6.0L. Sure, we’d all love to have a forged crank, rods and pistons, but the reality is  most normally aspirated, and many turbo builds (thanks to the Big Bang testing) stick with the stock internals. We decided to go this low(er) buck route, though there are a great many affordable forged options currently available for the LS.

Our build started out life as most 6.0Ls, with the base workhorse LQ4. Rated by the factory in the low 300-hp range (depending on application and year), the LQ4 featured reduced static compression (compared to the LQ9) thanks to a combination of dished pistons and sizable 71cc chambers on the 317 cylinder heads. On the plus side, the 317s shared the 243 ports, so they offered decent flow, even in stock form. The LQ4 also featured the mildest cam profile, early versions sharing the wimpy stick with the 5.3L LM7.

Given the limitations of the LQ4, we decided that any upgrades to the 6.0L must include both compression and cam timing, but we threw in cylinder head flow just for good measure. While it was tempting to toss on a set of factory LS3 heads and call it a day, we decided to port the already decent 317 truck heads. The first order of business was to disassemble, clean, and machine (as necessary) the high-mileage block. The boys at L&R Automotive were given the nod and, as it turned out, they came to the rescue on more than one occasion.

First off, they saved us some money by indicating the cylinder walls were in decent shape, requiring only a minor hone to true up. Next, they offered up a set of late-model (Gen IV) 6.0L, flat-top pistons and rods from a customer that had recently upgraded to forged components. Though the floating pins and revised rod design (said to be stronger) were welcome, what we liked most was the fact these LQ9 slugs were in good shape and would help us raise compression with their flat-top design.

The 6.0L short-block was finished off with a balance job, a fresh set of bearings, and a new Total Seal ring package. In addition to the rod and main bearings, Fel Pro supplied the needed rebuild gaskets (including MLS head gaskets), timing chain, and oil pump.

Having successfully upgraded our LQ4 to LQ9 status, we decided it was time for further improvements. With the short-block at the ready, we added airflow and cam timing. The mild factory cam was replaced by a stout piece from COMP Cams. The 54-454-11 cam offered a .614/.624 lift split, a 227/243-degree duration split, and 113-degree lsa. Originally designed for a rec-port application, the extra exhaust duration increased power production higher in the rev range. The cam was installed with a new set of standard-travel lifters from COMP Cams combined with 7.35-inch hardened pushrods (7.35-inches) from Speedmaster.

The cam swap showed promise, but not without some additional flow, so we shipped out the 317 heads to Total Engine Airflow for some massaging. Treated to their Stage 2 porting, peak flow numbers for the 317 heads increased by more than 70 cfm, with substantial gains through the entire lift range. In addition to the impressive porting, the TEA heads also featured a 2.04/1.57 valve package, custom PAC springs (required for our cam choice), and titanium retainers. The TEA stuff has never failed to produce excellent power, and we liked the fact the cathedral-port heads offered considerably more average power potential than a set of factory LS3 heads.

With our long-block complete, it was time for induction, exhaust and the final components needed for dyno testing. The low-buck method would be to utilize the early truck intake, but an even better option would be to add the Trail Blazer SS intake. We chose door number three and stepped all the way up to a FAST LSXR. Shown in testing (on a 6.0L) to be as much as 40 hp over the early truck intake, we didn’t want to limit the power potential of your new TEA heads and COMP cam.

The LSXR was fed by a FAST 102mm Big Mouth throttle body. Exhaust chores were handled by a set of 1 ¾-inch QTP headers feeding 3-inch OD collector extensions. As is our standard at Westech, no accessories were run and cooling was provided by a Meziere electric water pump. Fuel for the 6.0L was supplied by a set of 75-pound injectors from FAST, controlled by an XFI/XIM management system. The Gen IV truck crank was configured with 24x crank trigger and combined with the 1X cam sensor. Other than the new oil pump, the factory oiling system was left intact, including the truck pan, pick up, and windage tray.

LQ4 on the Floor 6.0L Build The 6.0L was originally offered by GM to replace the 454 big-blocks, and we can see why. These motors offer impressive torque and once modified, can produce even more. After upgrading the compression, cam, and induction system on the 6.0L, we eventually coaxed nearly 550 hp and more than 480 lb-ft of torque. Hardly peaky, torque production from the 6.0L exceeded 450 lb-ft from 3,800 rpm to 6,300 rpm. That was quite a jump from the 400 hp produced by your average LQ4 under the same conditions.

LQ4 on the Floor 6.0L Build
The 6.0L was originally offered by GM to replace the 454 big-blocks, and we can see why. These motors offer impressive torque and once modified, can produce even more. After upgrading the compression, cam, and induction system on the 6.0L, we eventually coaxed nearly 550 hp and more than 480 lb-ft of torque. Hardly peaky, torque production from the 6.0L exceeded 450 lb-ft from 3,800 rpm to 6,300 rpm. That was quite a jump from the 400 hp produced by your average LQ4 under the same conditions.

After a few break-in cycles and tuning, our LQ4 on the floor produced peak numbers of 549 hp at 6,700 rpm and 481 lb-ft of torque at 4,900 rpm. That, my friends, was one heck of a truck motor!

Sources: ARP, Arp-bolts.com; COMP Cams, compcams.com; FAST, fuelairspark.com; Speedmaster, Speedmaster79.com; Total Engine Airflow, totalengineairflow.com; Total Seal, totalseal.com

About Elizabeth Puckett

Elizabeth Puckett is a seasoned writer and hardcore gearhead. She was born with motor oil in her blood and a passion for everything that goes fast, especially if it's also loud and smells of race gas.