$275.00 – $775.00
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Rod Mod Only
During the “Rod-Mod” process, we take the LS3 intake manifold and install radius bars lengthwise in the plenum. Through research and development, we have learned that air does not like moving over sharp turns – it creates unwanted turbulence. The radius bars we install are carefully selected, measured, and cut to a specific length and assists in transitioning air from the main plenum into the runners. This helps to maintain proper airflow and velocity. In addition, we minimally grind and smooth the area inside the runners where the injector boss protrudes into the runner, ensuring minimal disturbance to airflow from the injector boss. The Rod-Mod is ideal for forced induction applications, as well as nitrous applications as it does not compromise the structural integrity of the manifold during high-pressure events.
Est Gains: 6 HP for bolt-ons & 12 HP for cammed setups.
Ported Rod Mod (Popular)
During the “Ported-Rod-Mod” process, we begin by removing the vertical stands that run inside the manifold plenum. These stands are large and very obstructive to flowing air. Once removed, we adequately seal the plenum floor back up, and slightly grind/smooth the floor of the plenum. Next, we port the air inlet section of the manifold along with grinding/smoothing the injector bosses protruding into the runners. Once all porting/grinding work is completed, we then install the same carefully selected radius bars that we use in the Rod-Mod. Again, these bars greatly assist with transitioning air from the plenum into the runners, maintaining maximum airflow and velocity. The Porting-Mod is ideal for naturally aspirated applications and performs at its best in a cammed setup. At no point do we recommend the Porting-Mod for forced induction or nitrous applications, as the stand removal does lessen the structural strength of the manifold.
Est Gain: We don’t see significantly more peak power over Rod Mod (+1 or 2 HP), but we see it across the entire powerband and the midrange torque increase is worth doing the Porting Mod if you can.
Induction
We have often wondered and been asked if porting in addition to the radius rod addition would improve the LS3 intake manifold. We figured it would be a great time to find out – so Mike and Ryan quickly built 2 manifolds, one with just rods and the other with the stands removed and ported. Both we and our customers have tested the radius rods on chassis dynos and at the track many times and usually see from 6 to as much as 12 RWHP. We saw 11HP at 6600.
Both we and our customers have tested the radius rods on chassis dynos and at the track, and usually see from 6 to as much as 12rwhp. We saw 11rwhp at 6600.
The ported version looked quite a bit better. We were disappointed with the positive result as the porting is very labor intensive and it’s probably going to be requested a lot going forward. Although we didn’t find significantly more peak power, but we got it everywhere and the midrange torque increase was worth the effort.
We didn’t find significantly more peak power, but we got it everywhere and the midrange torque increase was worth the effort.
The “Mod My Manifold” option allows you to send in your LS3 / L99 Intake Manifold in to us (shipping instructions below) to have the modifications completed. This option is best for the individual who doesn’t use their car as a daily driver, or can stand for the car to sit for a short period of time – while we are modifying your manifold. This is the least expensive option. Typical turn time is around 2 weeks.
The “Buy Modded Manifold” option is our most popular option – because it doesn’t require any downtime at all. We send you one of our modified manifolds from inventory.
We will optionally buy your stock LS3 manifold back for $350. Just send yours back in the box you received yours in. It’s that easy! When we receive yours (and verify it is not damaged…) you receive your core refund back.
If you decide to ship us your stock manifold back for the $350 credit – pack up and ship your intake manifold to:
Gwatney Performance
200 Municipal Dr
Jacksonville, AR 72076
Please include a copy of your invoice in the box with your manifold.
Please remove all vacuum hoses and sensors from manifold before shipping.
We HIGHLY recommend using generous amounts of shipping peanuts / bubble wrap. We’ve had a few “less than cautious” packing jobs (thrown in a box and taped up) which led to manifolds getting damaged in shipping. Unfortunately we are unable to issue core refunds on broken / damaged manifolds.
Induction
The test numbers are on a stock headed LS3, the radius rods smooth out turbulence in the intake manifold. It is not for a support deal. We have seen guys run them on a boosted application with no failure but do not suggest it with the center supports removed. The rods would no be beneficial at that time. We see a lot of our customers sell the ported manifold and go back stock when they add the boost.
You will not be able to make that intake fit properly. It will need to be replaced with a square port manifold. If in a truck, look for one from a 6.2 Denali or Escalade.
You will receive the $350 back from the total you are seeing on your screen.
The average turn around time for the porting service is 2-3 weeks.
Yes, it is the same as the L99, there will be no problem doing the exchange program for yours. We ask for the return back within 30 days.
Hey Peter. We've not modified one before so it is hard to know for sure. The "LS2 style" manifolds don't flow quite as well as the LS3 manifolds, but we'd assume it would be pretty close.
The epoxy on the floors is smoothed out and installed from the outside of the manifold. It's not going to come loose and go into the ports. We have seen competitors manifolds epoxy around the rods come loose and cause a valve to hang open and hit a piston.
Hey Mike. The ones that are epoxied in are the ones we have seen issues with. The epoxy breaks loose and goes into the engine. We heat the tip of the rod, run it through the back of the manifold and epoxy on the outside. The screws on the TB side are tacked in place so will not come loose. Ours have nothing that can come loose and go into the engine.
That's a good question. Doing the rod mod and porting increases the plenum volume and that flow into the runners, then it should.
Harry,
Yes, you should be able to fit the LS3 style intake, as well as we should be able to modify yours!
Thanks,
Malcolm,
We have not developed one to accept the 102mm TB yet!
Thanks,
GPI Team
Rick,
I'm sure we could work something out, give us a call at 501-985-4947, or email at support@gwatneyperformance.com
Thanks,
Sergio,
Thanks for reaching out! A painted intake manifold, although otherwise stock, would not be an acceptable core return!
Thanks,
GPI Team
Thanks for the question! The GPI Port-mod Intake will not require additional tuning. However, the ported throttle body could require calibration adjustments.
Thanks,
GPI Team
Joseph,
Thanks for the question! The modified intake will still vent the same, you'll still hook the EGR hose up at the same port!
Thanks,
GPI Team
We sell a large volume of the LS3 Intake Manifold Mods (of which a good majority of them are daily driven) - with no failures that we are aware of.
Unfortunately there are several differences between the LS3 Intake Manifold and the L76's. The Intake Mod cannot be performed on the L76 Intake Manifold.
We can either modify the LS3 manifold on your car - by selecting the "Mod Mine" option on this page, or we can send you a modified LS3 Manifold, and you could send us back your LS3 Manifold as a core - by selecting the "Exchange" option.
If you have any questions, feel free to email us at support@gwatneyperformance.com or call the shop @ (501) 985-4947.
Have a question about the next step of your build, a product, the status of an order, or anything else? Here is the place to ask! I’ll funnel your question to the correct team.
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Kenneth Hunter (verified owner) –
As always GPI knocked it out of the park. This intake PERFORMED, I done back to back dyno pulls with a FAST 92 and it effortlessly made more HP/TQ all around than the FAST. Highly recommend. Thanks again!
Kevin Pranger (verified owner) –
The quality of workmanship is outstanding and it is at a very affordable cost.
angel santiago (verified owner) –
The intake came out perfect!
Robert J. (verified owner) –
Intake perform great and noticeable gain
Anonymous (verified owner) –
I can feel the difference after the install and tune