Engine Guides / LS Engines

LQ4/LQ9 Engine Upgrade Guide: Expert Advice for LQ4 & LQ9 Mods to Maximize Performance

[Editor’s Note: Because the LQ4 and LQ9 engines are so similar, we’ve combined them for this engine upgrade guide, which is part of a series of LS engine upgrade guides assembled by a team of LS experts at Summit Racing that we are sharing at OnAllCylinders. For a primer on the entire LS engine universe, read LS Engines 101: An Introductory Overview of the Gen III/IV LS Engine Family.]

Intro to the LQ4 and LQ9 Engines

Meet the weapon of choice for big boost.

The LQ4 and LQ9 are Gen. III, 6.0L, iron block, truck engines.

The LQ4 served in anything from bread-vans and boats to SUV’s between 1999 and ’07. It started off life like any normal truck engine. Iron heads, small cam and the old SBC crank rear flange thickness. That changed in 2001 when GM threw in the bigger cam and aluminum heads designed for the LQ9.

The LQ9 was introduced in 2002 for the Cadillac Escalade and was found in top-of-the-line trucks until 2007. It cranked out 345 horsepower, had 10.1:1 compression, and had other nice features like full-floating pistons.

To chart the changes in the LQ4 or LQ9 over the years, check out these articles:

How to Get More Power From Your LQ4 or LQ9

These engines start life in trucks, but there’s just as much of a chance that you’ll spot them under the hood of a turbocharged drag car. Because of their strength, these engines are likely to see a power-adder sooner than later.

These engines are some of the most popular GM LS engines for several reasons:

  • With iron block strength, they are the first choice for boost or nitrous applications.
  • GM made a bazillion of them which helps keep prices down.
  • Gen. 3 engines didn’t have AFM (Active Fuel Management) or VVT (Variable Valve Timing), so you don’t have the expense of an AFM or VVT delete kit.
  • The heads flow similarly to LS6 heads, but have bigger chambers making them boost friendly.
  • Displacement—364 cubic inches to be exact.

Do they have a downside? Just one. At 216 pounds, the block is 100 lbs. heavier than the aluminum LS1 block.

GM LQ4 block

Basic Bolt-On Upgrades for LQ4 and LQ9

Trucks are the everyday hotrods of the 21st century.

For a lot of people, it starts off with a cold air intake and aftermarket exhaust. The problem is that the engine starts to sound REALLY good and owners find themselves wanting to go faster.

Trucks often come with mechanical fans that sap horsepower. An electric fan kit will free up the power. All these can be done in the garage, but the tune won’t be optimized.

At this point, we recommend you talk to your chassis dyno tuner and decide on a computer programmer. Whether you’re towing on low-octane or springing for good fuel, a tuner can dial the ECM and take it to the next level. It also makes it easier tune for a bigger cam and injectors later on. Before you go, make sure to install a colder thermostat to open up the tuning window.

Below are more upgrades that will improve the performance of the LQ4 and LQ9 engines.

Upgrading the LQ4/LQ9 Camshaft and Valvetrain

Regardless of whether you add a power-adder, the original camshaft is small and should be jettisoned immediately.

LQ4 camshafts

An LS3 or LS9 cam makes good power, but not where you want it. What you need is a cam that delivers a gut-punch right where the converter hits. We recommend a dedicated truck cam.

What’s the difference?

To maximize torque in the mid-range, manufactures close the intake valve at about 40 degrees (@.050 in.) after bottom dead center and alter the intake valve opening to set the idle quality. The bigger the engine, the smoother it will idle for any given cam, which is why you’ll see the 6.0L LQ4 and LQ9 engines getting slightly bigger cams than the 5.3L engines.

Intake Duration (@ 0.050 in.)Horsepower at the wheels after bolt-onsIdle QualityNotes
197° (Stock)250-270 whpSmoothHeavy drivetrain.
215°+50 hpSlightly noticeableGood with auto and stock converter.
220° - 230°+75 hpSteady lopeConverter recommended. Still can drive daily.
230° - 240°+100 hpLopeyFly-cutting the pistons may be required. Heads and intake good for another 50+ hp.

Drop-in .500 in. lift cams are popular, but LS6 springs allow you to run .550 in. lift and extend the rpm range. Spring life isn’t a problem because trucks generally don’t spend a lot of time at high rpm. Beyond that, .575 to .600 in. isn’t a problem with dual valve springs.

The stock rockers are good to 175 lbs. of seat pressure and 450 lbs. open. You will want to install a trunnion kit for added reliability.

There are a few other parts needed for a LQ4/LQ9 cam swap such as an LS2 timing chain, LS7 spec lifters, LS2 timing chain damper and adapter, and .080 in. wall pushrods.

LQ4/LQ9 Power Adders

In general, the LQ4 and LQ9 will see boost or nitrous before serious head work. Before we get into the power adders…there’s a couple things to address:

  • A 4-corner steam kit reduces hot spots that cause the rings to butt and snap the piston’s ring lands.
  • Any power will put you well past the limitations of the stock injectors and pump. We’ll address those in the next section.

Okay, with that out of the way, let’s get to the fun stuff.

  • roots-style supercharger is dependable and makes great torque in the low- and mid-rpm range. It’s great for melting tires.
  • centrifugal-style supercharger is lightweight and makes more power at high rpm. This is partially due to a larger intercooler mounted in front of the radiator.
  • nitrous oxide kit (at low settings) is great for street driving with stock internals. Up to a 200 shot is common. Keep in mind the tight piston ring-gap is the limiting factor beyond that. If you’re wanting to get serious, a single plane intake is less prone to break from a nitrous backfire. A plate system has better distribution than the original intake, but an eight-nozzle fogger system is even better. Running higher octane fuel is advised.
  • Truck engine bays make fitting turbos easy. Single turbo systems using turbo exhaust manifolds are an inexpensive way to make big power. If you’re running a single turbo, the T4 hot-side fits well, but the small turbine diameters limit exhaust flow. The 650whp begins to feel like 400 did in a hurry, so take this into consideration. V-band style exhaust housings open up the turbine options and make plumbing easier. Although twins are a little more expensive out of the box, you’ll have more room to grow.

Upgrading the LQ4/LQ9 Fuel System and Tuning

The factory injectors are only rated at 25 lbs. and won’t support much more than 380 hp.

Plan on upgrading to larger fuel injectors to meet the fuel demands of increased power. Custom tuning will be required to properly adjust the fuel and ignition timing.

Keep in mind, the best injectors are fully characterized which helps your tuner maximize idle quality etc.

When running boost, you can use a water-methanol system to supply extra fuel and lower charge air temps.

The factory pump is good to about 430 whp. Many fuel system upgrade options are available. Drop-in fuel pump modules and external pumps are popular. Other options to maintain or increase pump pressure includes electronic voltage controllers and hotwire kits.

Upgrading the LQ4/LQ9 Intake Manifold and Throttle Body

If you have a power adder, the intake and throttle body can take a backseat for a while longer. If you are naturally aspirated though, it’s commonly done before the heads.

The factory truck-style manifold has long runners for better low-end torque. Porting the intake is one option and a good value.

If you’re looking for more power and torque, the Trailblazer SS intake is a step up and a larger 90mm 4-bolt throttle body can be fitted. The F.A.S.T. LSXRT intake allows a bigger 102mm+ throttle body. Truck engine bays also accommodate Tunnel Rams. These trade a little bit of torque down low for more up high—and nothing looks cooler.

Manifold StylePeak HorsepowerTorque
Single Plane+10 hpLosses everywhere below 5500 rpm. *Only recommended for nitrous or boost.
F.A.S.T. LSXRT+25 hpMore low-end and top-end.
Tunnel Ram+35 hpSlightly lower below 3000, equal at 4500, and big gains beyond 5500.

Ask your tuner about going with a Speed Density tune. Doing so removes the MAF restriction and will give you a bit more power.

[Trying to find an LS engine for a swap or build? Check out Part 1 and Part 2 of our LS Spotter’s Guide.]

Upgrading LQ4/LQ9 Cylinder Heads

  • The stock heads can be CNC ported for more airflow and milled up to .030 in. for more compression. Flow numbers can be as high as 325 cfm at .600 lift. Lightweight hollow stem LS3 valves can be cut to 2.000 in. to fit the seats. Between the light valves and better springs, the engines will pull cleanly to 7000 rpm.
  • Although LS3 heads fit, the valves are shrouded and the increase in power isn’t what the flow numbers would suggest. You would also need a rectangle port truck intake to retain the torque and clear the accessory drive.
  • A better option is aftermarket cathedral port heads. They reduce down time, they’re all new, and you can usually offset the added cost by selling your original heads. Valve angles are typically laid over to 13.5 degrees and 2.100 in. intake valves are common. They flow great and the cross-sections are great for boost. When comparing heads, look at .400 lift numbers as a general indicator of how the heads will perform. With a medium-sized cam, 450+ whp naturally aspirated is common even with the heavier truck drivetrain.

Upgrading the LQ4/LQ9 Rotating Assembly

LQ4 engine crankshaft


Still looking for more?

As mentioned before, the pistons are a weak point and you probably know a guy that’s popped one. A set of forged pistons should be high on your priority list. They have stronger wristpins, thicker ring lands, and the added valve reliefs allow you to run big cams.

There are exceptions, but Gen. 3 rods start getting dicey around 750 whp and the bolts don’t like much more than 7000 rpm. If you’re getting forged pistons, it’s best to also get forged connecting rods with 7/16 rod bolts.

The LQ4 and LQ9 cranks were cast but strong. They’ve been known to handle over 1000 whp. The main reason for going with a stroker forged crank is for the added cubic inches. The extra cubes bring boost on quicker which means you can use bigger turbos.

Performance rotating assemblies are available in many combinations.

A couple notes of caution:

  • The 6.0L iron blocks had short cylinder sleeves (5.430 in. on average). Much of the piston skirt drops out of the bottom of the cylinder at BDC. The best piston manufacturers have compensated for this by eliminating skirt taper until a point well above where it meets the bottom of the cylinder sleeve at BDC. Any skirt taper at this intersection acts as a razor blade and quickly wears out the piston.
  • The blueprint deck height of the block is 9.240 in., but it’s common to find them in the 9.230-in. range. It’s best to measure deck height before ordering your rotating assembly. Thicker head gaskets or using an aftermarket 6.098-6.100 in. rod will ensure enough piston-to-head clearance.
Engine SizeBore Dia.Piston Comp. HeightStrokeRod LengthWristpin Dia.
6.0L (364 c.i.d. stock)4.000 in.1.338 in.3.622 in.6.098 in..9431-.9449 in.
6.7L (408 c.i.d.)4.030 in.1.110 in.4.000 in.6.125 in.0.927 in.

Upgrading the LQ4/LQ9 Engine Block

There is no replacement for displacement. The cylinders can be safely over-bored 0.030 in. When combined with a 4.000-inch stroke, this will increase c.i.d. to 408 cubic inches or 6.7L.

The blocks have been known to withstand 1300 whp with proper machining, racing fuel and an excellent tune. Head and main studs are advised if you’re making more than 850 whp.

The factory main caps aren’t doweled. It’s better to reduce ignition timing and compensate with added boost to reduce the cylinder pressure spikes that lift heads and cause the main caps to dance.

(Information for this article originally appeared in this Upgrading the Gen. 3, 6.0L, Iron Block, LS Truck Engines article at Summit Racing’s searchable database of FAQ tech infoGo there and search “LS engines” for a comprehensive collection of LS engine tech information.)

NOTE: You can find engine specs and detailed engine upgrade advice for every LS and LS-based Vortec truck engine in one place: The Definitive Guide to LS Engine Specs and LS Engine Upgrades.

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  1. Pingback: LQ9 Engine Specs: Performance, Bore & Stroke, Cylinder Heads, Cam Specs & More - OnAllCylinders

  2. Pingback: LS Engines 101: An Introductory Overview of the Gen III/IV LS Engine Family - OnAllCylinders

  3. My 2000 series 2500 LQ9 has 404000 miles still runs smooth as a Cadillac, though I do keep rpm below 2500. It routinely passes smog in ca, keep waiting for it to give up, it doesnt, still delivers pulling heavy construction loads

    • Jason Brenton says:

      My ’03 Escalade has 320,000 on it and I drive it like its stolen every day, all day. I expected it to blow 100k miles ago and it keeps on going. Although, I noticed today that the head gasket is likely blown, hence the research on rebuilding…

      • Joe Sanford says:

        My 02 Escalade now has 340K and my Sierra has 245K on its LM7 5.3 and has a rear main seal leak, which led me to just pull it ALL spend $12K on a “hotrod” LQ4 (540hp crank) and 4L80e transmission upgrade so I will be good for another 300K 🙂 Love the LQ4 6.0L engine, had one in my Hummer H2 also and never any issues!!

  4. Jason Powell says:

    I have an lq4 and an LAS supercharger. Need the best pistion crank and rods to use that wont break the bank. Also are gm ls3 heads with an ls9 cam good enough to get me 500hp. I need to know what combo to buy that will get me 700-750hp thanks fir your help

    • Texas speed racing look for forgery steel rotating assembly for lq4. call them they will help u take about a month for delivery.

  5. Danial Miller says:

    I have a 6.0 in a 2005 Chevy 2500 HD. The actual manufacturers date reads 10/2004. I would like to know if this engine is a gen 3 or 4? Does it have floating pins and better rods?
    Either way is nice, but would love to know for fact.

  6. Pingback: Ask Away! with Jeff Smith: Money-Saving Tips for LS Swapping a '66 Chevy II - OnAllCylinders

  7. Brian Nutter says:

    Jason Powell, Summit just released a line of Pro LS Forged pistons. They are excellent quality and the best value. They come in versions for Gen. 3, Gen. 4 and Aftermarket 6.125 rods. You can read about them here: https://www.onallcylinders.com/2019/02/01/pro-ls-profile-summit-racing-makes-choosing-forged-piston-ls-engine-easy/

  8. Brian Nutter says:

    Daniel, it is likely a gen. 3 engine. 2003 t0 2005 involved several changes. The easiest place to spot them is here: https://www.onallcylinders.com/2019/02/01/pro-ls-profile-summit-racing-makes-choosing-forged-piston-ls-engine-easy/

    As for whether it’s Gen. 3 or not, the cam sensor is behind the intake on a gen. 3 and the knock sensors are in the valley. No plugs on the front cover. Gen. 4’s have a cam sensor on the front cover (and sometimes VVT) and the knock sensors are on the passenger side.

  9. albert doyle says:

    I have a 2003 2500HD 6.0, I bought an engine out of 2000 cast iron engine. Will my 03 aluminum heads bolt up? What gasket kit do I use to if I can use heads?

  10. Jeff Mann says:

    I have 2005 GMC Yukon Denali AWD. Wanting to do cam swap and possibly LS3 heads. I’m looking at tick flow for heads. But I use as my daily driver and pull a inclosed trailer on occasions. What do you prefer on cam size and should I use truck flow for heads n cam or do you have any suggestions?i don’t have tons of money I just want a good product. Thx

    • Check out Vinci cams, their trucker cam is great, and I plan on upgrading my cam and springs with their parts soon on my 03 Denali

  11. Jeff Mann says:

    I have 2005 GMC Yukon Denali AWD. Wanting to do cam swap and possibly LS3 heads. I’m looking at trick flow for heads. But I use as my daily driver and pull a inclosed trailer on occasions. What do you prefer on cam size and should I use trick flow for heads n cam or do you have any suggestions?i don’t have tons of money I just want a good product. Thx

    • Simon Barrow says:

      I went with a Brian Tooley Racing Stage 1 cam in my LQ4.

      Their customer service was very knowledgeable and a big help.

  12. Devon Thomas says:

    I would like to turn my 350/5.7 vortec into a LS motor (if possible)

  13. Steve bradford says:

    Can a 2004 SS Lq9 6.0 plug and play into a 2005 Ls Lq4 model truck without modifications?

  14. Ken Strait says:

    I swapped from 5.3 to LQ 9 in my 2001 Silverado . Bored block 030 over forged pistons went with cam valve lift intake 515 ex 522 duration intake 259 ex 265 it’s LS 1 XR 259 HR -12.
    Long tube headers with 3 inch mandrel bend back cat . stock 5.3 truck intake . New rockers and push rods new rod and main bearings .
    Tuned by Jeff Skinner LS tuner Baton Rouge.
    Everyday driver averaging 15.8 to and from work .
    373 rear .
    I would like more power however realize trans will need beefed up .
    Thoughts ?

  15. Looking to get 500 whp through a t-56 In a c10 pickup and an lq4. NA or supercharged is how I’d like to go. Also if it’s na, I wouldn’t mind going with a carb either but trying to get a path to head down. Thank you for any input.

  16. Danial Miller says:

    To chime back in, the 6 liter in the 05 model 2500 truck was a gen 4 style. It had floating wristpins, the better rods. However, every main bearing in it was scarred and no oil pressure. Somebody probably ran it without oil. I sold the motor and truck. Now planning on installing a 99 model 6 liter in a 69 Corvette. Was looking at cam ideas, and stall options for the 4L80e. Those converters are expensive!

  17. Tim Pedigo says:

    I have a 2013 LQ4 that I would like to add a little power and cleaner look for the injection. It is currently in my 54 Chevy truck and have very limited space in front of my Holly accessory drive assembly for the 4″ intake tube. added height here would help to clear the electric fan. any suggestions?


    • There are some aftermarket manifolds that are high rise and will clear the accessory drive but then you run into hood issues. Some just cut us the factory power steering bracket to clear. A little modding and it can be done. Aftermarket tensioners and pulleys may be necessary.

  18. Bradley Rob Sauceda says:

    What I’m banging head on is,the throttle body and intake.so I purchased a sheet metal intake and a 102mm tbody. My pedal will not communicate with the tbody.
    2005 Cadillac Escalade Lq9 ECM and harness

  19. I’m doing a LS swap in my 57 Chevy bel air.
    Things are going good. What is the best rad design to use for my car , place it where the old rad was or put in in front of where the old rad was and add electric fans. ????

    • electric fans are generally better for driving in traffic and provide great performance without the hp loss of a convential hydro fan or fixed blade. That is the route I would go. And if you want to save a few more hp, an electric water pump is good for a few more ponies.

  20. Pingback: LQ4 6.0L Engine Specs: Performance, Bore & Stroke, Cylinder Heads, Cam Specs & More

  21. Has anyone ever installed 706 head on the LQ4. I have a set I can install . But my plan is cam swap with truck cam , comp springs ,lifters tray, chain ,pump . And I fear above a 93 octane. Even though I have HP tuner. Any advice greatly appreciated

  22. working a 2004 GMC 2500 HD With LQ4 turn out at 70,000 mile the lifters starting to fail on Number #4 cylinder causing a miss at idle .

    Si will be pulling heads off to replace lifters and may need valve job.

    Will sense i will be diving into motor what can I do for a little more power and still pass smog.

    Thanking you in advance. Ron

  23. Corey Osgood says:

    I have a 2000 Sierra 2500 LQ4 with 340k miles and a knock. Should I build a higher compression LQ4 or try to find an L92/L94 to swap in with ECU/harness? More power/torque would be nice, but better fuel economy would make me really happy.

    • A rotating LS assembly kit from Summit Racing would be my recommendation. Build a stroked version of what you have now and it will be bullet proof using forged internals. A good cam that stays below 0.500″ lift and you can use your stock heads and valve train.

  24. Pingback: Extra Stuffing! Our Top 10 Engine Swap Projects - OnAllCylinders

  25. Heriberto P Avila says:

    Very helpful

  26. I keep looking for an engine combo with good compression height for nitrous\blower application. These stroked solutions recommended do not seem to be conducive to proper ring pack distancing from the crown of the piston. 1.110″ compressions heights can not support 0.40″+ ring distances. Please point me in the right direction if I am wrong. The stroked LM7\383 and both LQ7\LQ9 402cid solutions suffer this issue.

  27. Pingback: LQ9 Engine Specs: Performance, Bore & Stroke, Cylinder Heads, Cam Specs & More

  28. Have a 2005 Yukon xl Denali with the LQ4 6.0L what other factory parts will give me a little more hp and torque? Like what factory gm heads, intake, etc will swap directly over with very little no modifications? Don’t have a lot of money basically want to do cheap salvage yard upgrades/swaps.

  29. Steve Hinkle says:

    I want to send out a big thank you to Brian for this information. I referred to it regularly while upgrading my 1999 Chevy Silverado 2500 4×4 with a 6.0L. Using this info, I was able to spec aluminum heads with a larger combustion area and larger valves along with a performance cam & shorty headers. After a custom tune and an exhaust repair, the increase in hp is noticeable. I also am former USAF and again, thank you.
    Camshaft & shorty headers – summitracing.com
    Aluminum cathedral port heads
    Custom tune – Eden Automotive Tucson, Arizona / Evan (5700+ tunes to date)

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