Huge L83 & L86 NA Head & Cam Performance Gains (+100rwhp!)

LT’s are the new LS’s!

The performance truck market continues to grow at a staggering rate – with huge popularity going back to the early LS trucks.

The L83 (5.3L) and L86 (6.2L) performance potential is especially promising due to these modern generation LT engines offering so much more power and technology than its predecessor in a factory trim. For instance, a L83 powered 5.3L truck starts out 50 HP stronger than it’s 5.3 LS counterpart –  giving you a much better starting point with these engines!

That being said – there is always room for improvement right?

Intake Manifold & TB Upgrade (a MUST L83 Upgrade!)

RWHP & RWTQ GAINS

  • Direct L86 Manifold & TB Swap on L83: 9 RWHP / 6 RWTQ
  • Ported L86 Manifold & TB Swap on L83: 17 RWHP / 9 RWTQ

During our R&D process with the L83 (5.3L) engine, we discovered that the intake manifold and throttle body from the L86 (6.2L) was a direct bolt-on application for the L83 (5.3L)! The ports lined up perfectly, with the main difference between the two being: runner length and plenum design.

We immediately picked up 9 RWHP and 6 RWTQ. After noticing great gains in simply bolting on the L86 (6.2L) intake manifold and throttle body, and observing significant obstruction in the manifold stands, we decided to port the intake manifold and test again. (Note that we did not port the throttle body, just the intake manifold.) Testing the ported version, we were able to pick up another 8 RWHP and 3 RWTQ, for a total gain of 17 RWHP and 9 RWTQ!

Camshafts and Install Packages

RWHP & RWTQ GAINS

  • Low Lift Cams: Up to 60 rwhp / 30 rwtq
  • High Lift Cams: Up to 90 RWHP / 45 RWTQ

All of our Direct Injected camshafts incorporate a larger fuel lobe, going with the informal industry standard of 32% larger. We’ve specifically ground these cams to utilize our GPI Phaser Plugs (in either a 4° or 0° block-out).

With our truck cams, we’ve stayed with our proven low-lift cam design. We have found – the majority of our customers want the sound and added power, but still want to retain that 100,000 mile durability. Our low-lift cam grinds are more gentle on valvetrain, yet still offer great gains in power. These low-lift cams are designed to work with the factory pushrods and run on a factory LT1 valve spring.

Of course, we do offer all of these cams in a high-lift version as well, for those seeking an all-out performance build!  The high-lift cams offer the same drivability mannerisms as their low-lift counterparts, but offer an increase in power due to the higher valve lift.

RWHP & RWTQ GAINS

  • L83 Heads: Up to 25 rwhp / 15 rwtq
  • L86 Heads: Up to 30 rwhp / 15 rwtq

When it came to designing a cylinder head package for our L83 (5.3L) truck customers, we kept the ports small in order to emphasize port velocity. This has allowed us to see significant power increases under the curve, not just in the high RPM range.

Our L86 (6.2L) cylinder heads utilize our proven CNC porting program that we run on our LT1 cylinder heads, while we developed a new porting program for the L83 (5.3L) cylinder head.

Several milling options are available, and we highly recommend that piston-to-valve clearance is properly checked in any milled application.

During our porting process, we want to ensure that we provide you – the customer – with the greatest and most reliable product that we can. This is why we install guide liners and precisely grind the liners to achieve optimal valve to guide clearance. All of our cylinder heads also receive a valve job – grinding the valve seats to custom angles. In addition to the cylinder heads being cleaned, deburred, etc., the bowls are hand-blended on every set of cylinder heads.

Torque Converters

Converter Recommendation

  • 258mm Converter for both 6L80 and 8L90 (for most applications)
  • 245mm for all out track builds
  • 3000-5000 stall based on driving style (lower improves street manners / higher improves 60ft times)

When it comes to converter options for the DI trucks, we relied on our history and relationship with Circle D Converters to choose the perfect converter for these applications. As a standard, we recommend a 258mm converter, with stall speeds between 3000-5000 on a “B” stator.

In lighter, race applications, the 245mm converter is still a viable option as well!

Drop-In Pistons (for supercharged / turbo / nitrous applicaitons)

This kit includes:

  • Support up to 1000 RWHP applications
  • 6.125 Compstar Connecting Rods
  • Heavy Duty Pin, Locks, and Ring Package
  • Diamond Pistons with 2618 Forging Material
  • Maintains OE Compression of 11:1
  • Thick Wall, Heavy Duty Wrist Pins
  • No Balancing Required! Drop In Piston and Rod Upgrade!!

Much like our well-known LT1 Drop-in Piston/Rod package, we’ve developed a drop-in package for the 5.3 L83 engine as well! These new pistons will feature a Diamond Racing piston, forged from 2618 alloy, and come complete with pins, clips, rings, and valve reliefs. They will maintain a factory compression ratio of 11:1 and utilize the same Compstar rods as our LT1 package. Of course, all of this will be a zero-balance install for a true drop-in application! Look for this new package in the coming weeks, along with a “how-to” video illustrating the proper way to file-fit the rings!

Recent L83 (5.3L) Build

One one of our recent L83 builds we were able to observe significant performance gains from our L83 (5.3L) cylinder heads, camshaft, and intake manifolds.

On the baseline pull our test truck began with 308 RWHP and 338 RWTQ.

Here’s the complete list of mods:

After completion, we ended with 402 RWHP and 396 RWTQ, for gains of 94/58 respectively. Our peak HP was observed at around 6400 RPMs, with peak TQ at around 4800 RPMs.

Before and After Dyno

L83 Head & Cam (Stage 3) Idle Sound

Rather build a turbo truck?

We’ve got you covered too!

Ready to start building your L83 or L86 GM Truck?

We’d love to help!  If you have any questions – just shoot us an email at support@gwatneyperformance.com or call us at (501) 985-4947!

35 thoughts on “Huge L83 & L86 NA Head & Cam Performance Gains (+100rwhp!)

  1. Jason says:

    With a build for your 402 rehoused, can you tune this to go with a stage 2 magnusen supercharger? What you think the final rwhp/rwtq be?

    • Ryan Stevens says:

      Hey Jason, we certainly can tune for the Maggie setup in house, we don’t remote tune power adder applications remotely though.

      With the addition of 7-8 psi you likely would be in the 550-575 whp range on this same setup. Drop in pistons and rods certainly recommended from a durability and longevity standpoint.

    • Ryan Stevens says:

      The 2020 engine/PCM is more complex with the dynamic fuel management and ECM unlock requirements. Tuning is going to be far more expensive firstly, and the cam kit is going to be different than previous years. I would recommend looking for a pre-19 setup to transplant due to better parts availability and tunability.

    • Ryan Stevens says:

      This same setup with our high lift version of the Stage 4 cam/ported heads and increase in compression. Flycutting will be needed. Flex fuel and supporting bolt on mods of course.

  2. Phillip Bangma says:

    I have a 2019 chev silverado 5.3ltr, I would like a cam for street driving, would like to stick with stock converter, what is the most cam that you would recomend

  3. Zachary Coburn says:

    I have a 2018 Silverado 5.3 4×4. It’s good at stock but I would like to make some extra power. What would yall recommend for it and if going to high would I need to get the trans built for it to handle a lot of power?

    • Ryan Stevens says:

      With good tuning the trans should live a long happy life. Some of the easiest power gained would be headers, cai, flex fuel, and tuning. That is an easy 50 rwhp in modifications. From there our cam kits and head porting service offer substantial gains of another 50 plus rwhp.

  4. Mark Collins says:

    Thank you for sharing! Is it true the current LT series of GM engines are ticking time bombs around 100k? The root cause being GDI, lifter and cam issues from cylinder deactivation plus burning oil? Thanks again.

    • Ryan Stevens says:

      Not from our experience. With GDI there are certainly issues with carbon/oil deposit buildup on the valve, but that can be maintained with routine cleaning. Otherwise the engines are reliable. We have seen some cases of some faulty valve springs from the factory, but that has been isolated to the newer run over the last year or so. I personally have a 17 model with almost 70k miles of cruising and towing and could not be happier with how it performs and how efficient it is!

  5. Vj says:

    How bought Your stg1 cam on a l83 with a procharger around 14psi with LT1 injectors and upgraded intank pump..really like to keep stock converter.what do you think bout this combo an where do you think I would be power wise?

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