LQ4 Short Block - 480 HP For $3,775

This is what the plastic lifter... 

   

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This is what the plastic lifter holders look like in the engine. Once the new cam is in place, replace the pushrods and push down slightly. This will reseat the lifters and then the entire rocker shaft assembly can be torqued in place. This is a net-lash system, so you don't even have to lash the valves.

Test Time
Right out of the used-engine cradle and onto our dyno test stand with the carburetor, MSD ignition conversion, and headers, this otherwise bone-stock 6.0L small-block maintained no less than 400 lb-ft of torque from 2,200 to 5,400 rpm and managed to crank out a peak torque of 439 at 4,400. On the horsepower side, the little 366 cranked out an impressive 425 hp. Generally, a 355ci Gen I small-block would need a healthy cam and some good heads to pull off power numbers like these. This power was encouraging but not really surprising. Because we knew the cam was tame, the next step was a GM Performance Parts Hot cam with specs that most enthusiasts would classify as mild at best.

The cam swap was also easy because we didn't have to remove the intake. All factory Gen III and Gen IV engines come with trick plastic sleeves that will capture the lifter in the up position so the cam can be removed without yanking the lifters out of their bores. While there is talk of the need for specialty tools to line up the front timing-chain cover to the oil pan, engine-dyno-swap specialist Ed Taylor merely eyeballs the parts and they work with nary a leak. We had the cam swapped and the valvetrain back in place while the block was still warm to the touch.

The GMPP Hot cam also comes... 

   

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The GMPP Hot cam also comes with a complete set of LS6-spec valvesprings that offer some additional spring rate to control the valves at 6,000 rpm.

With the cam safely dialed in and the engine singing, our second dyno session went as smoothly as our first. The difference was the power. Even with the mild cam, the 6.0L responded with an average of 11 more lb-ft of torque, with the peak gaining the same amount, arriving at a slightly higher 5,000 rpm. The real surprise was the huge horsepower gain. At the 6,000-rpm peak-horsepower point, the 6.0L cranked out an additional 58 hp, peaking at 483. That's a mere 17 hp away from the magical 500hp level. Try as we might, we couldn't push the little 366 any higher, but that's still a plenty impressive achievement.

Now, before you get all excited about this first test, you'd best start saving your nickels and dimes in anticipation of what we're going to do next. We'll give you a hint: We made a bunch more power and didn't spend nearly what you'd expect. If that doesn't hook you, check your pulse

This chart lists the stock cam specs for the stock, iron 6.0L RPO LQ4 engines (there are two different cams used depending on the year of the engine) as well as the dimensions for the GM Performance Parts Hot cam. Note the wide LSA used on the OE cams. This greater angle reduces overlap and contributes to a very smooth idle. The power increase generated by the GMPP cam can be attributed to both the longer duration and the tighter lobe separation angle that increases overlap.

The Hot cam offers not only 25 more degrees of intake and 21 more degrees of exhaust duration at 0.050 but also adds 23 more degrees of overlap plus another 4 degrees with the tighter LSA for a total of 27 degrees. These numbers are generated at 0.050-inch tappet lift. This is a big factor in the power increase. And this is still a very mild cam at only 219/228 degrees at 0.050.