Chevrolet C6 Corvette LS -LS3-LS7

Mangum Racing 267cc LS3 Cylinder Heads

Mangum Racing CNC Ported MR 15° LS3 Cylinder Heads

Built from our 6-bolt 15° LS3 casting featuring increased deck thickness, the MR 15° LS3 is engineered for serious naturally aspirated and boosted combinations that demand airflow, strength, and repeatability — while maintaining OEM valve angle and valve location geometry.

This casting is designed to support 1,500+ horsepower combinations when paired with the proper short block and induction system, making it an ideal solution for builders who need maximum performance without moving away from stock valve layout.

Each set is fully CNC ported in-house on new Centroid 5-axis machining centers and finished on Newen seat and guide equipment. Every cylinder head is hand blended, inspected, and assembled in small batches to ensure dimensional accuracy and consistency.

Airflow Performance

Tested on a SuperFlow bench with a 4.125” bore plate

Intake (Radius Entry)

• .200” – 148 CFM
• .300” – 227 CFM
• .400” – 282 CFM
• .500” – 325 CFM
• .600” – 350 CFM
• .700” – 363 CFM

Exhaust (No Pipe)

• .200” – 114 CFM
• .300” – 164 CFM
• .400” – 200 CFM
• .500” – 233 CFM
• .600” – 240 CFM
• .700” – 243 CFM

With a 267cc CNC intake runner and optimized 96cc exhaust port, the MR 15° delivers strong mid-lift efficiency and stable high-lift airflow — ideal for aggressive hydraulic roller and race-oriented camshaft profiles while retaining factory valve geometry.

Premium Hardware & Construction

• 6-bolt Mangum Racing LS3 casting with increased deck thickness
• 15° valve angle with OEM LS3 valve spacing
• 2.165” hollow stem stainless intake valves
• 1.600” hollow stem stainless exhaust valves
• Bronze guides
• PAC .660” dual spring package
• Titanium retainers
• Viton seals
• 1.250” steel spring seats
• 68.5cc CNC chambers (milling available at no charge)
• Chamber softening options for 4.000”, 4.065”, and 4.125” bore sizes
• Flat milling at .006” per cc
• Minimum bore: 4.000”

Built for High-Output Stock-Geometry Combinations

The increased deck thickness provides added durability under elevated cylinder pressure, while the 15° valve angle maintains compatibility with stock-style piston valve reliefs and factory-based valvetrain geometry.

The PAC .660” dual spring system offers the stability required for serious street or race camshaft profiles, and stock pushrod length works in many applications (final length should always be verified based on camshaft and milling).

For builders who need to retain OEM valve angles and locations but demand serious airflow capability, the MR 15° LS3 casting delivers.

Mangum Racing 275cc 11° LS3 Cylinder Heads

Mangum Racing CNC Ported MR275 11° LS3 Cylinder Heads

Built from the Mangum Racing 6-bolt 11° LS3 casting featuring a massive .750” deck surface, the MR275 is designed for maximum-effort naturally aspirated and boosted LS combinations where airflow, strength, and valvetrain stability are non-negotiable.

This casting was engineered for builders who want every available advantage — valve angle, deck thickness, port efficiency, and piston-to-valve clearance — all optimized to support serious compression and high cylinder pressure environments.

Each set is fully CNC machined in-house on brand new Centroid 5-axis machining centers and finished on Newen seat & guide equipment. Every head is hand blended, inspected, and assembled in small batches to ensure repeatability and precision.

Airflow Performance

Tested on a SuperFlow bench with a 4.125” bore plate

Intake (Radius Entry)

• .200” – 143 CFM
• .300” – 221 CFM
• .400” – 283 CFM
• .500” – 330 CFM
• .600” – 358 CFM
• .700” – 381 CFM

Exhaust (No Pipe)

• .200” – 112 CFM
• .300” – 161 CFM
• .400” – 202 CFM
• .500” – 232 CFM
• .600” – 242 CFM
• .700” – 248 CFM

With a 275cc CNC intake runner and optimized 98cc exhaust port, the MR275 delivers exceptional mid-lift efficiency with dominant high-lift airflow. The 11° valve angle significantly improves piston-to-valve clearance, allowing aggressive cam timing and higher compression strategies without compromise.

Premium Hardware & Construction

• 6-bolt Mangum Racing 11° LS3 casting with .750” deck thickness
• Optimized 11° valve angle and revised valve locations
• 2.185” hollow stem stainless extended-length intake valves
• 1.600” stainless extended-length exhaust valves
• Bronze guides
• Choice of PAC 1207X, 1208X, or 1209X dual spring packages
• Titanium retainers
• Viton seals
• 1.250” steel spring seats
• 70.5cc fully CNC chambers (milling available at no charge)
• Chamber softening options for 4.000”, 4.065”, and 4.125” bore sizes
• Flat milling at .006” per cc
• Substantial piston-to-valve clearance for advanced camshaft profiles and compression increases
• Minimum bore: 4.000”

Built for Maximum Effort Combinations

The increased deck thickness supports extreme cylinder pressure in large displacement and boosted applications. The revised 11° valve angle enhances airflow efficiency while providing additional mechanical clearance — a critical advantage in high-rpm, high-lift camshaft programs, or builds where smaller combustion chambers are required.

These heads have supported combinations exceeding 2,000 horsepower and 200+ mph in competition environments, making the MR275 a proven solution for serious LS3-based builds.

If you are building a no-compromise LS3 combination — naturally aspirated or power-adder — the MR275 was designed for exactly that purpose.

All Precision Race Components (PRC) cylinder heads come fully CNC-ported and machined using state-of-the-art technology!

Click Here to SEE why we build better heads!

MADE IN THE USA!!

CAST IN THE USA!!

MACHINED IN THE USA!!

PRC's aftermarket casting LS3/L92/L99 cylinder heads come standard with the following options:

• NEW PRC 13-Degree Valve Angle LS3 Castings
• Improved Piston-to-Valve Clearance For Extra Compression & Larger Camshafts
• Smaller Than Stock Intake Port Volume For Improved Port Velocity
• Manley Stainless 2.185" Intake, 1.60" Exhaust Valves
• Billet Rocker Pedestals
• TSP .660" Dual Spring Kit w/ PAC Valve Springs, Titanium Retainers, Seats, & Seals
• CHE Bronze Guides
• Completely Assembled and Milled to Your Specifications
• 60-68cc Chambers

All PRC cylinder heads are extensively researched and tested. The all-new PRC aftermarket casting LS3 cylinder heads are designed to flow considerably more than a gm ported casting while keeping the port sizes smaller for improved port velocity. The result is a cylinder head that is smaller than a stock GM LS3 port and moves more air than any other ls3 cylinder heads! 

The all new PRC aftermarket casting LS3 heads are the perfect option for customers looking for the ultimate in LS3/L99/L92 cylinder head technology

The PRC aftermarket casting LS3 cylinder heads are available in 2 different configurations: 

• 255cc Runners for max effort stock cube LS2/LS3/L99/L92 engines looking for a 370cfm cylinder head that can be aggressively milled & still keep better than stock p/v
• 260cc Runners For LS3/L99/L92 stroker engines needing a 380cfm+ cylinder head!

The 13-degree valve angle will allow for the ability to run more compression and larger camshafts thanks to additional piston-to-valve clearance!!  

With all PRC cylinder heads, quality and performance are our two highest priorities! In addition to performance, you will not find a better performing set of cylinder heads at this price (cost is for the pair!). Call one of our sales consultants today if you have any questions or if you would like to discuss your specific application.