At GPI, we’re constantly asked “What’s the best intake manifold for my Gen 5 LT?” The honest answer has always been “it depends on your application,” but we decided it was time to put real data behind that answer. We recently completed comprehensive dyno testing of five popular Gen V LT intake manifolds to help you make an informed decision for your build.

The Test Setup

Our test engine was designed to represent a typical modified LT1 found in a C7 Corvette or 6th gen Camaro:

Stock bottom end LT1
Heads milled .050″
Valve reliefs added with our fly cut tool
.040″ head gaskets
SS4 cam with 0-degree limiter
VP112 fuel due to stock LT1 fuel pump and injectors

We tested from 4,400 to 7,400 RPM to capture a usable average for comparison, considering most applications would have appropriate stall speed converters to make the data meaningful.

All manifolds were tested with identical conditions — same throttle body, target air/fuel ratio, timing curve, and comparable coolant and oil temperatures. The graphs presented are unsmoothed and generated from raw test data. While we typically prefer a 3-pull average for more attractive and accurate results, in the interest of time, we felt single pulls would provide reasonably useful information.

The Contenders

We tested five intake manifolds with varying runner lengths:

Holley Hi-Ram – 6.5″ runner length
Performance Designs PTR – 9″ runner length
BTR Mid Length – 6.5″ runner length
CID LT Big Bertha – 6.125″ runner length
Harrop ITB – 13.5″ runner length (Individual Throttle Bodies)

Performance Results

Intake Manifold	Average Torque (4400-7400 RPM)
Performance Designs PTR (9″)	572.2 lb-ft
Holley Hi-Ram (6.5″)	562.1 lb-ft
BTR Mid Length (6.5″)	556.2 lb-ft
CID Big Bertha (6.125″)	548.9 lb-ft
Harrop ITB (13.5″)	532.6 lb-ft

Table 1: Average torque production across test RPM range

Performance Designs PTR – The Best Overall

The PTR with carbon lid produced the best average torque of 572.2 lb-ft through the test RPM range. With a runner 2.5″ longer than the Hi-Ram combined with a larger plenum volume, the PTR is right at home in this RPM range. This manifold delivers exceptional mid-range torque that most street/strip combinations will appreciate.

Holley Hi-Ram – The High-RPM Champion

The Hi-Ram performed admirably with an average torque production of 562.1 lb-ft. What’s particularly interesting is that the Hi-Ram closes the gap and overtakes the PTR at around 7,000 RPM. For more radical engines with higher desired RPM ranges, the Hi-Ram would show clear benefits. This manifold remains a proven performer and excellent choice for high-winding applications.

BTR Mid Length – The Hood-Friendly Option

The BTR Mid Length proved very comparable to the Hi-Ram, with the significant advantage of fitting a 6th gen Camaro without modifying the hood. This is a nicely finished component with a port fuel option at a very competitive price point. For enthusiasts who want to keep their hood intact while still achieving serious power gains, this is the manifold to check out. The short runner version gives up too much torque for most street/strip combinations in our opinion, but the mid-length version solves that problem perfectly.

CID Big Bertha – The Max Effort Manifold

The CID LT, affectionately nicknamed “Big Bertha,” was designed as a maximum-effort tunnel ram style manifold with burst plate and port fuel provisions for power adder applications. It features customizable runners for various cross-sections and lengths, and can accommodate a 112mm throttle body for big cube/high RPM naturally aspirated applications. It also boasts the largest plenum volume of any LT manifold currently on the market.

This test wasn’t really in the CID’s wheelhouse, but we wanted to see how it performed anyway. The manifold tested was an as-cast version with a 103mm throttle body top. With its slightly shorter runner and large plenum, it closes the gap at 7,200 RPM — about the same time the valvetrain is reaching its limit on this engine. This manifold is an excellent choice for maximum-effort power adder applications or custom big-inch naturally aspirated projects. Like the Hi-Ram, it will stick out of the hood and make a statement if that’s your style, but it’s not for those who treasure their bonnet, as they say across the pond!

Harrop ITB – The Future Contender

We were initially reluctant to include the Harrop ITB in this test. However, it was the manifold that was leaving our shop on this engine at the customer’s request due to the “cool factor” for his classic V-drive boat application, where the low-end torque would work well regardless of peak numbers.

Important caveat: This was an LS3 manifold adapted to the LT1 head and was less than ideal from a port alignment and transition perspective. Without question, if this manifold were a properly designed LT1 version, it would have developed substantially more torque to 6,000 RPM than any of the other manifolds we tested. We were mainly interested in how the runner length would impact the torque curve, but this wasn’t a fair fight. A properly designed LT1 Harrop would be substantially better, and we understand from our Australian friends that one is in the works. Stay tuned!

Choosing the Right Intake for Your Application

Based on our testing, here are our recommendations:

Best Overall Mid-Range Power: Performance Designs PTR – Perfect for street/strip applications in the 4,400-7,000 RPM range
Best High-RPM Performance: Holley Hi-Ram – Ideal for radical engines that operate above 7,000 RPM regularly
Best Hood Clearance Option: BTR Mid Length – Excellent performance without requiring hood modifications on 6th gen Camaros
Best for Power Adders: CID Big Bertha – Maximum plenum volume and customization for forced induction applications
Best for Low-RPM Torque (Future): Properly designed LT1 Harrop ITB – Wait for the dedicated LT1 version

Conclusion

As we suspected, there is no single “best” intake manifold for all applications. The Performance Designs PTR takes the crown for average torque production in the typical street/strip RPM range, making it an excellent choice for most modified LT1 applications. However, the Holley Hi-Ram’s high-RPM advantage, the BTR’s hood clearance, and the CID’s max-effort capabilities each have their place depending on your specific needs.

The key takeaway is matching the intake manifold’s characteristics — particularly runner length and plenum volume — to your engine’s operating range and intended application. Whether you’re building a street-driven C7 Corvette, a drag-focused 6th gen Camaro, or a maximum-effort power adder project, there’s an intake manifold in this test that will optimize your combination.

For more technical information or help selecting the right intake for your build, contact us at [email protected]. We’re here to help you make the best choice for your specific application.