So we excavated an orphan LQ4: a really ancient 1999 version with iron heads. It literally was an orphan because nobody wanted it. Our buddy Bill Irwin found this neglected engine leaking on the floor of a shop in Iowa. It is perfect for a Car Craft build; Bill sored the long block for a demon-of-a-deal at $550. We dubbed it the Iron Maiden.

The plan is to burn through a sequence of tests on this cast-off engine with an emphasis on affordability and on making torque and streetable power. To this point, we will avoid using a large-by-huge camshaft combined with rectangle port heads and a carbureted single plane intake manifold. While that combination would make really good peak power, it will be a bit of a pooch at part-throttle. The Iron Maiden is aimed at making great torque where you can really use it.

We'll tease you a little bit here just to motivate you to follow this entire series of stories. Coming soon, we'll tell you how we made nearly 500 hp with just a few budget parts that centered around a pair of lightly-ported production cylinder heads, a mild cam, and a stock, truck-style intake manifold. Have we got you wondering? Good.

First off, why did we buy an LS engine with iron heads? Because it was cheap. We also knew we were going to swap heads, so after this first round of tests, those iron castings were destined to become door stops.

Prior to our session on the engine dyno, we disassembled the Maiden and inspected her closely because recently, we were bitten by a pair of spun rod bearings on a used 5.3L truck engine we tested. The spun bearings ate the crank, and that stinging reminder left us questioning the Iron Maiden's stability under dyno abuse. Of course, because we made the effort to inspect her, the internals were prefect. However, we did decide to install new rod, main, and cam bearings along with a new timing chain and oil pump, while the engine was apart. Those were the only new parts we used- the old pistons and rings went back in along with the stock cam, lifters, and pushrods. If anything, the new bearings cost us horsepower because we tightened the bearing clearance, as evidenced by its 89 psi hot oil pressure at 6,000 rpm. It takes horsepower to push an oil pump that hard. We will address that later in the series.

We wanted to run the engine on the dyno in a totally stock configuration for a baseline, which demanded a stock wiring harness that we ordered from Painless Performance. A big advantage to using Painless is that once you've purchased a harness, you can send in your stock ECU to have it unlocked and to change other details like gear ratio or tire size. The stock fuel injection system does require the use of a mass airflow sensor (MAF) and inlet ducting, which we sourced for a 2002 truck in the Spectre catalog. RockAuto supplied the mass airflow sensor. This system also requires only one pair of oxygen sensors as Painless deleted the after-cat sensors. Another change we made was to add a set of larger fuel injectors from an 8.1L (496ci) truck engine. They flow 30 lb/hr at 58 psi, where the stock injectors flow roughly 25 lbs/hr and are good for about 400 to 425 hp before going static.

Once we installed the engine at Westech and dyno operator Steve Brule' allowed it to warm up, we discovered the stock fuel pressure regulator peaking at 70 psi. We replaced it with a new one, which brought the fuel pressure down closer to normal, but later we installed an adjustable regulator to compensate for the larger fuel injectors.

The 8.1L injectors allowed for more horsepower potential, but running in our otherwise stock engine meant that the tune-up was too rich. The best way to fix this would be to go reprogram the ECM with the new fuel injector flow rates, but this requires investing in tuning programs like HP Tuners, LS Edit, or JET's software. Our temporary solution was to install an adjustable fuel pressure regulator. By turning down the fuel pressure, we could manually reduce the flow through the injectors. At this point by tuning strictly with fuel pressure, we made a decent 383 lb-ft of torque and 330 hp.

Steve Brule' suggested converting to Holley's HP EFI system; Westech has that set-up in their dyno cell, and he's very familiar with it's tuning process. Because we have more than a dozen changes planned for this engine, we agreed and will be using that engine management system for the remainder of all the tests. After hooking up the HP ECM, power jumped to 365 hp and 412 lb-ft of torque, an increase of 35 hp and 29 lb-ft.. This is because we were able to correctly set the fuel maps to reflect the fuel injector size and flow, and give the engine a more aggressive timing curve. Remember, the Maiden is still stone stock, right down to her cast iron manifolds and accessory drive.

Next, we removed the stock accessory drive and water pump, replacing it with an electric pump. We didn't except much until the results came in with a surprising average increase and a peak improvement of 10 hp. We've seen this before on a 4.8L engine recently, and our theory is that truck water pumps pull more power at the higher engine speeds, perhaps because they cavitate. The engine's peak numbers improved slightly to 416 lb-ft and 373 hp at 5,200 rpm. We used to really work hard on a small-block Chevy to get to that number remember this is with the LQ4's stock cam and intake manifold.

A bigger cam was in order now, so we removed the stock LQ4 cam and replaced it with a Corvette LS6 version with a nice duration and lift increase. On the intake side, for example, the LS6's 204 degrees of duration is an increase of 13 degrees over the LQ4's specs. See the full comparison in the accompanying Cam Specs chart. With the cam change, peak torque jumped to 435 lb-ft while horsepower climbed to a solid 430. That's an improvement of 19 lb-ft of torque and 55 hp - all from a production cam! Considering that we started at 330 hp, that's a gain of 100 horsepower.

For the final test for this first session was to add a set of 1 5/8-inch shorty headers from Summit Racing originally intended for an early 6.0L truck. We thought these would deliver a slight bump to the power curve. Instead, we saw the power drop off slightly- an unexpected outcome. We didn't realize until later that we had one badly bent pushrod and two others that were tweaked. This would account for the slight loss of power. We attributed this to the weak stock springs we had left on the stock iron heads that couldn't handle the more aggressive LS6 camshaft. Yes, in case you might have forgotten, we're still running those iron 6.0L heads with their 140,000-mile valve springs, a situation we will remedy in the next installment.

So within a very short period of time, we have restored our Iron Maiden's virtue and have sent her on the road to becoming a true diva. In its near-stock state it now makes 435 lb-ft of torque and a solid 430 hp, still with that clunky, truck intake manifold. But don't fret, we're about to test a couple more very affordable manifolds, and you can plan on seeing some whippin' power numbers. We'll just leave you with that little tease for next time. A horsepower number north of 450 hp is certainly there for the taking.

See all 16 photos

See all 16 photos This is where we started a greasy 1999 6.0L all-iron LQ4. We don't know where it came from or the stories it could tell, but we got it cheap, it was in decent shape, and that's all that matters.

See all 16 photos Upon teardown inspection, the sloppy stock timing chain was no surprise. We replaced it just to give the Maiden a fair shot at making power.

See all 16 photos We've been burned before by a used LS engine that spun the rod bearings soon after dyno testing started, so we decided to thoroughly inspect our 6.0L. After disassembly, we cleaned everything and installed new cam, main, and rod bearings along with a new timing chain and oil pump. We reused the original rotating assembly and stock 6.0L truck cam. Our long-time school buddy Bill Irwin helped in the reassembly.

See all 16 photos We wanted to start the test session with a completely stock engine so Painless Performance supplied this new 6.0L 24x truck harness and configured our stock computer at no extra cost. That is part of the service when you buy a new harness.

See all 16 photos With the engine re-assembled, we bolted it to a Summit Racing engine test stand and fired it up using the Painless wiring harness, stock computer, and a Spectre inlet system that includes a MAF. Amazingly nothing fell off and it fired right up.

See all 16 photos Early 1999-2000 6.0L engines employ this longer crank flange that emulates the flange position of a small-block Chevy. This allows you to bolt an early Chevy automatic like a TH350 / TH400 directly to the 6.0L flexplate with no adapters.

See all 16 photos Once up on the dyno at Westech, we ran the engine in its stock configuration including the iron exhaust manifolds and a pair of mufflers.

See all 16 photos Running the engine bone stock included configuring the engine with the Painless wiring harness, the stock ECU, and an inlet system from Spectre. We didn't have the time or the resources to refine the stock ECU except by changing fuel pressure, without tuning software, we were unable to change the timing.

See all 16 photos Stock truck 6.0L injectors flow 25 lb-hr at 58 psi. We used a set of 8.1L injectors instead that measure 30 lb-hr at 58 psi. With a BSFC of 0.45, this allows us to run these injectors at 58 psi up to around 480 hp before they max out. Our testing revealed BSFC's in the high 0.380's, which might allow us to run these little injectors up to 525 hp.

See all 16 photos We removed this truck accessory drive (Test 2) and replaced it with an electric water pump and picked up 10 hp but power also improved almost everywhere. A previous test with a 4.8L motor also responded similarly. We think the truck water pump cavitates at higher engine speeds, which demands more power to drive the pump.

See all 16 photos Steve Brule' installed the LS6 cam with practiced ease. As you probably know, the LS lifter trays allow you to remove the cam without removing the lifters from the valley. This is nice because to remove the lifters requires yanking the heads! Steve hedged his bet with a set of Powerhouse lifter retainer tools just so a lifter didn't drop into the pan.

See all 16 photos The stock exhaust manifolds were surprisingly good to 425 hp. We changed to these shorty headers from Summit and the test results report that we lost power. We later found bent pushrods that we're positive occurred on this test. The real results are probably slightly better than the Test 3 cam swap.

See all 16 photos Only later when swapping to different cylinder heads (in Part II) did we realize that we had bent three pushrods, which is why the power was down slightly with the shorty headers.

See all 16 photos This is a screen shot of the Holley HP ECU fuel flow map we were using to tune the 6.0L. It's hard to see, but at 5,500 rpm we were commanding 206 lbs/hr.

Cam Specs

Camshaft Duration at 0.050 Valve Lift Lose Separation Angle (LSA) LQ4 -1999 - Int. 191 0.457 116 LQ4 - Exhaust 190 0.466 116 LQ4 -'01-'04 - Int. 196 0.457 114 LQ4 - Exh 207 0.457 114 LS6 - '02-'04 - Int. 204 0.555 117.5 LS6 - Exh 218 0.551 117.5 Show All

Because our engine was a 1999 LQ4, it uses the early cam specs. If our LQ4 had been a '01-'04 version, the baseline power would have been higher due to the slightly better timing figures.

See all 16 photos

Dyno Numbers

Test A (not shown) stock 6.0L with GM ECU 383 lb-ft at 4,100, 330 hp at 4,900

Test 1 stock 6.0L with Holley HP ECU - 412 TQ, 365 HP (+29 TQ, +35 HP)

Test 2 Removed accessory drive 416 TQ, 373 HP (+4 TQ, +8 HP)

Test 3 Add LS6 camshaft 435 TQ 430 HP (+ 19 TQ, + 57 HP)

Test 4 Add shorty headers 430 TQ 424 HP* (-5 TQ, -6 HP) *bent pushrods

RPM TQ1 HP1 TQ2 HP2 TQ3 HP3 TQ4 HP4 2600 372 184 371 183 352 174 352 174 2800 378 202 376 200 360 192 357 190 3000 393 225 391 223 376 215 371 212 3200 399 243 400 244 382 233 379 231 3400 400 259 402 260 389 251 385 249 3600 406 278 409 280 400 274 396 272 3800 411 297 414 300 412 298 408 295 4000 412 313 416 317 419 319 417 318 4,200 412 329 416 333 426 340 421 337 4,400 409 343 415 348 430 360 426 356 4,600 406 356 412 361 432 378 428 375 4,800 399 364 405 370 435 397 430 393 5,000 384 365 391 372 435 414 429 409 5,200 368 364 377 373 426 422 421 417 5,400 348 358 357 367 416 428 412 423 5,600 328 350 337 360 403 430 397 424 5,800 307 340 318 351 388 428 381 421 6,000 351 401 Avg. 385.4 301.8 389.6 305.9 403.6 325.7 398.1 324.5 Peak 412 365 416 373 435 430 430 424 Show All

Average TQ increased 12.7 lb-ft

Average HP increased 22.7 HP

Peak TQ increased 23 lb-ft

Peak HP increased 65 from 365 to 435

Parts List

Description PN Source Price Used LQ4 iron 6.0L N.A. friend's shop $550.00 Painless truck wiring harness 60218 Summit Racing $768.99 Used 8.1L fuel injectors 17124531 eBay $150.00 Holley HP ECU 558-500 Summit Racing $1,120.95 Holley EFI harness for LS 24x/1x 558-102 Summit Racing $382.96 Holley harness for LS truck injectors 558-214 Summit Racing $153.95 Sniper fuel rail LS1 850005 Summit Racing $114.95 Summit shorty LS headers SUM-9021 Summit Racing $199.97 Hooker cast iron LS exhaust manifolds 8501-HKR Summit Racing $299.00 Stock LS6 camshaft Friend $50.00 Melling stock timing chain 3SRH60 RockAuto $16.12 Comp Hi-Tech pushrods, std. length, 7.400" 7955016 Summit Racing $131.97 ARP head stud kit 234-4110 Summit Racing $359.16 ARP head bolt kit 134-3609 Summit Racing $199.93 ARP crank bolt 234-2503 Summit Racing $34.57 Fel-Pro head bolt kit (1 side - need 2) ES72173 RockAuto $17.12 AC Delco replacement crank bolt 917139 RockAuto $2.75 Mass Airflow Sensor (MAF) MA145 RockAuto $80.79 Spectre fresh air inlet kit for truck 9900 Summit Racing $162.89 Fel-Pro intake gasket, cathedral port MS9801GT RockAuto $33.75 Fel-Pro LS 6.0l MLS head gaskets, each 26192PT Summit Racing $38.97 Fel-Pro header gaskets 1440 Summit Racing $21.99 Valvoline 10w40 oil, 5 qt. 779309 AutoZone $27.99 Fram Extended Guard oil filter XG3675 RockAuto $7.10 Show All