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!)


  • 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


  • 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.


  • 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 [email protected] or call us at (501) 985-4947!

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

  1. Barry says:

    I have a 2016 GMC Sierra that I just sent 2 rods out of at 760whp turbo. Selling the kit and I’ve decided I want to build an aluminum block 6.6, l86 block with full l8t rotating assembly. The truck is 8l90 swapped, with a ctsv3 converter. I would like to use the biggest cam possible for most power possible without having to upgrade the converter. What cam would be recommended?

  2. Dennis Backherms says:

    What would it take to get 450 out of this motor? Would that still be considered a daily driver? What about physically deleting the DOD?

    • Josh says:

      I’m running another company’s stage 2 cam, had my heads ported locally still with stock valves, a holley hi-ram, nick williams 102mm throttle, longtubes, katech oil pump, S&B cold air, without VVT, and without a torque converter upgrade(though I need one)and I make 460 RWHP. Also be aware that your driveshaft will need to be upgraded and most shops won’t even dyno the truck with the stock driveshaft.

  3. Derek Wendt says:

    What is the total cost after install at your shop for the 402hp setup? I love the sound but tow a 7600lb travel trailer fairly regularly. How would the converter handle that?

    • Ryan Stevens says:

      This setup is more for high performance straighline applications. It is not suitable for towing. You would want to stay with our stage one cam, and stock converter for towing applications.

    • Ryan Stevens says:

      The fact is that the increased displacement would be more beneficial in a truck application because of the substantial increase in torque. From this point you could do the same round of mods and end up over 100 rwhp stronger.

    • Josh says:

      I saw 460 wheel with my combination compared to the 420 crank of the L86. The bigger displacement of the L86 will always offer more power if you plan to mod it, but if you’re asking cost of a modded L83 vs a stock L86, the L83 COULD offer more power depending on your choice of mods. Another key point to remember is that if you leave the L86 stock, you could still see AFM failures, in which case modifying either the L83 or L86 would rectify this concern.

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