LQ4 Short Block - 480 HP For $3,775
All It Takes Is A Boneyard 6.0L Truck Engine With A Mild Hydraulic Cam, A 750 Holley Carb, And Headers To Get Some Serious Horsepower

This is a story that many traditional small-block Chevy guys don't want to hear. They think the new Gen III and Gen IV small-block engines from GM are too expensive to build and don't make that much more power than the old engines. The truth is that while these new-generation engines are different and the parts are sometimes more expensive, there are ways to make affordable power-big power. The more progressive car crafters have already embraced this new technology and are enjoying the powerful fruits of their willingness to try new things. While there's always room for both small-blocks, if you are serious about the horsepower game, it's no longer prudent to ignore these late-model engines. They thump.

We've been watching the used Gen III engine market for the last couple of years, waiting for the right time to jump into the new-Gen world. While these engines are metric and look a little funny compared with the tried-and-true small-block Chevys, the reality is they are still just four-stroke, two-valve motors. And in many ways, they are far superior to the engines we grew up with.

Most of the media attention has been focused on the aluminum 5.7L LS1 or the latest 6.0L LS2 engine. The LS1 is becoming more affordable every day, while the LS2s are still too new to be considered budget material. While all-aluminum means less weight, we wanted more displacement. This led us to the iron 6.0L truck engines. These 364ci motors are really just 4.00-inch-bore versions of the LS1 with iron blocks. As you can see in the displacement chart, the entire Gen III family is similar to the old-school 283-327-350-400 small-block family tree.

The 6.0L's larger 4.00-inch bore is important because we wanted to test the horsepower potential of the latest L92 heads that just came on the market from GM and are being used on the new '07 L92 truck engines. Because of their larger valves, these heads cannot be used on a bore smaller than 4.00 inches. But you'll have to wait until next month for that part of the story.

Even with stock iron truck heads, we were able to crank out over 480 hp with a mild cam from the carbureted 6.0L engine for less than four grand. We were impressed knowing that with more cam and some speed stuff, 500 hp was well within reach

The Used Motor Game
Our search for an affordable, used 6.0L engine led us to LKQ, a nationwide chain of recycling yards that offers take-out engines from late-model vehicles. In an online search, we found a 6.0L engine out of a truck for $1,100 at the LKQ in Santa Fe Springs, California. We were able to obtain the engine without the A/C compressor, starter, power-steering pump, and alternator but still with all the brackets and pulleys.

Since this is a nationwide chain, often the engines will be located in different states, which will require shipping. Shipping costs vary depending on how far the engine has to travel, but according to Brian Sebring of LKQ, they average between $225 and $275.

Among the engines we searched, we saw several 5.7L and 5.3L engines that would also make great starting points (for a little less money) if a 6.0L isn't to your liking. According to Sebring, the 5.3L engines can be had for less than $1,000 depending upon their condition. LKQ pulls the engines, tests them on a stand, and then sets them up on a pallet for shipping. It doesn't get much easier than that.

Of course, LKQ is just one source for used engines, but the company has 65 yards throughout the country, so it makes it easier to find the engine you want.

Inside an LQ4
The engine we chose to work with is the all-iron 6.0L Gen III small-block that appears in many different larger pickups and SUVs. Despite the fact that this is a truck engine, it offers more power potential than a typical LS1 5.7L engine because of its greater displacement and larger, 4.00-inch bore. The iron blocks are otherwise identical to their aluminum counterparts, are notably stronger, and add only 65 pounds. The stock LQ4 engines also use a lower 9.4:1 compression ratio compared with the 10.2:1 compression ratios offered in the LS1 engines. More rare but also out there is the Escalade LQ9 with more compression and more power. Other major differences in this LQ4 engine are the use of the taller EFI intake manifold, a deeper-sump oil pan, truck exhaust manifolds, and the truck-specific accessory drive. Because our first few tests were intended to be used with a carburetor on the engine dyno, the EFI manifold was not included. Even though the truck oil pan will not fit a Camaro or Chevelle engine swap, we left it in place for the dyno testing. The truck accessory drive was also not a problem to retain, but we had access to an F-car-style (Camaro/Firebird) front accessory drive, so that's what we used instead of the LQ4 version. Finally, we added a set of Kooks Gen III headers instead of the stock exhaust manifolds because we were assuming that most enthusiasts would run this engine with headers in an older musclecar.

6.0L Setup
One of the nice things about this new generation of engines is that they are extremely easy to work on. If you are planning on reusing the EFI manifold, it does not require gaskets, as the intake employs a reusable rubber O-ring seal around each intake port. In our case, we intended to use a carburetor, so we lifted the EFI manifold and installed the GM Performance Parts aluminum carbureted intake manifold. This manifold requires the usual gaskets, which Fel-Pro offers. On top of the manifold, we used our battle-tested-tough, Holley mechanical-secondary, 750-cfm 0-4779 carburetor.

Because the LQ4 6.0L is part of the Gen III family, it also uses the GM coil-near-plug distributorless ignition system. The quickest and easiest way to get a carbureted engine running is with MSD's timing/rev control box. MSD has come up with a small electronic box that "talks" to the GM smart coils and triggers them with the appropriate spark timing. The MSD can be fine-tuned for initial timing, as well as both "mechanical" and "vacuum" advance curves by making changes to a couple of very easy-to-understand timing graphs on a laptop computer. That sounds complex, but even we managed to figure it out within about 20 minutes and soon had our initial timing and a full advance curve dialed in.

We configured the engine this way to avoid dealing with the perception that this conversion is overly complex and expensive. The negative side to this plan was that the GMPP intake and MSD electronic conversion box were not cheap, adding more than $850 to the cost of our 6.0L engine. If you chose to retain the factory intake manifold, you could modify the factory electronic fuel and spark curves by using aftermarket tuning software, such as HP Tuner or LS1 Edit to achieve similar power levels. You wouldn't even have to change intake manifolds, since our experience is that the factory truck intake is especially good at making torque while sacrificing only a reasonable amount of peak horsepower. We decided to stick with a carburetor for this series of testing owing to its simplicity.
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.
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.

PARTS LIST
DESCRIPTION PN SOURCE PRICE
LQ4, iron 6.0L, used N/A LKQ $1,100.00
GMPP carb intake 88958675 Scoggin-Dickey 369.75
Fel-Pro intake gasket 1312-1 Summit Racing 22.69
Fel-Pro header gasket 1438 Summit Racing 26.36
GMPP Hot cam kit 12480033 Scoggin-Dickey 429.95
MSD ignition conversion 6010 Summit Racing 303.88
MSD extension harness 60101 Summit Racing 178.95
Carb, Holley 750 0-4779 0-4779C 415.95
Headers, Kooks, 131/44 65005 Kooks Headers 864.90
Pennzoil platinum oil 5W-30 Amazon 29.95
Fram oil filter 4967 Amazon 4.95
Total $3,747.33
OPTIONAL PARTS
Hooker 131/44 LS1 swap 2288-1HKR Summit Racing $629.95
CAMSHAFT DURATION
@ 0.050 LIFT
(INCHES) LOBE
SEPARATION
ANGLE (LSA)
'99-'00 LQ4, Int. 191 0.457 114
PN 12560967, Exh. 190 0.466
'01-'06 LQ4, Int. 196 0.467 116
PN 12561721, Exh. 207 0.479
GMPP Hot Cam, Int. 219 0.525 112
PN 12480033, Exh. 228 0.525
Gen III Family Tree
The following is a genealogy of sorts, listing the bore and stroke combinations for the popular GM Gen III engines. Starting with the 5.3L engines, the stroke is consistent at 3.622 inches, with the larger bore being the difference in the displacement.


ENGINE DISPLACEMENT
(CUBIC INCHES) BORE/STROKE COMPRESSION ROD LENGTH
4.8 293 3.78/3.268 9.5 6.276
5.3 325 3.78/3.622 9.5 6.098
5.7 346 3.898/3.622 9.5 6.098
5.7 346 3.898/3.622 10.1 6.098
6.0 (LQ4) 364 4.00/3.622 9.4 6.098
6.0 (LQ9) 364 4.00/3.622 10.0 6.098


Test 1 was with the stock, iron 6.0L short-block and production iron heads assisted with a GMPP single-plane intake manifold, a 750 Holley carburetor, and a set of 131/44-inch Kooks long-tube headers.

Test 2 kept all the original changes from Test 1 but added the GMPP hydraulic roller Hot cam and valvespring kit.


TEST 1 TEST 2
RPM TQ HP TQ HP
2,200 406 170 399 168
2,400 403 184 392 179
2,600 403 199 393 194
2,800 406 216 401 214
3,000 411 235 414 237
3,200 418 255 427 260
4,300 424 275 435 281
3,600 429 294 438 299
3,800 433 313 437 315
4,000 436 332 434 331
4,200 437 350 434 347
4,400 439 368 436 366
4,600 439 384 441 387
4,800 437 399 447 408
5,000 432 411 450 428
5,200 424 420 450 444
5,400 412 424 444 456
5,600 398 425 436 466
5,800 383 424 430 475
6,000 367 419 423 483
Avg. 417 318 428 336
Power/ci 1.20 1.16 1.23 1.32
(peak)