{"title":"LS3 Rectangle Port Cylinder Heads","description":"\u003cp\u003eLS3\/L92\/L99LSA\/LS9 Based Cylinder Heads.\u003c\/p\u003e","products":[{"product_id":"mangum-racing-267cc-ls3-cylinder-heads","title":"Mangum Racing 267cc LS3 Cylinder Heads","description":"\u003cp\u003e\u003cspan\u003eMangum Racing CNC Ported MR 15° LS3 Cylinder Heads\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003eBuilt 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.\u003c\/p\u003e\n\u003cp\u003eThis casting is designed to support\u003cspan\u003e \u003c\/span\u003e\u003cspan\u003e1,500+ horsepower\u003c\/span\u003e\u003cspan\u003e \u003c\/span\u003ecombinations 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.\u003c\/p\u003e\n\u003cp\u003eEach 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.\u003c\/p\u003e\n\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003eAirflow Performance\u003c\/strong\u003e\u003c\/summary\u003e\u003cp\u003eTested on a SuperFlow bench with a 4.125” bore plate\u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003eIntake (Radius Entry)\u003c\/span\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e.200” – 148 CFM\u003c\/li\u003e\n\u003cli\u003e.300” – 227 CFM\u003c\/li\u003e\n\u003cli\u003e.400” – 282 CFM\u003c\/li\u003e\n\u003cli\u003e.500” – 325 CFM\u003c\/li\u003e\n\u003cli\u003e.600” – 350 CFM\u003c\/li\u003e\n\u003cli\u003e.700” – 363 CFM\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cspan\u003eExhaust (No Pipe)\u003c\/span\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e.200” – 114 CFM\u003c\/li\u003e\n\u003cli\u003e.300” – 164 CFM\u003c\/li\u003e\n\u003cli\u003e.400” – 200 CFM\u003c\/li\u003e\n\u003cli\u003e.500” – 233 CFM\u003c\/li\u003e\n\u003cli\u003e.600” – 240 CFM\u003c\/li\u003e\n\u003cli\u003e.700” – 243 CFM\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eWith 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.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003ePremium Hardware \u0026amp; Construction\u003c\/strong\u003e\u003c\/summary\u003e\u003cul\u003e\n\u003cli\u003e6-bolt Mangum Racing LS3 casting with increased deck thickness\u003c\/li\u003e\n\u003cli\u003e15° valve angle with OEM LS3 valve spacing\u003c\/li\u003e\n\u003cli\u003e2.165” hollow stem stainless intake valves\u003c\/li\u003e\n\u003cli\u003e1.600” hollow stem stainless exhaust valves\u003c\/li\u003e\n\u003cli\u003eBronze guides\u003c\/li\u003e\n\u003cli\u003ePAC .660” dual spring package\u003c\/li\u003e\n\u003cli\u003eTitanium retainers\u003c\/li\u003e\n\u003cli\u003eViton seals\u003c\/li\u003e\n\u003cli\u003e1.250” steel spring seats\u003c\/li\u003e\n\u003cli\u003e68.5cc CNC chambers (milling available at no charge)\u003c\/li\u003e\n\u003cli\u003eChamber softening options for 4.000”, 4.065”, and 4.125” bore sizes\u003c\/li\u003e\n\u003cli\u003eFlat milling at .006” per cc\u003c\/li\u003e\n\u003cli\u003eMinimum bore: 4.000”\u003c\/li\u003e\n\u003c\/ul\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003eBuilt for High-Output Stock-Geometry Combinations\u003c\/strong\u003e\u003c\/summary\u003e\u003cp\u003eThe 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.\u003c\/p\u003e\n\u003cp\u003eThe 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).\u003c\/p\u003e\n\u003cp\u003eFor builders who need to retain OEM valve angles and locations but demand serious airflow capability, the MR 15° LS3 casting delivers.\u003c\/p\u003e\u003c\/details\u003e","brand":"Mangum Racing","offers":[{"title":"PAC .650\" Double Springs","offer_id":52550852968724,"sku":null,"price":2099.99,"currency_code":"USD","in_stock":true},{"title":"TSP\/PAC .660\" Polished Springs","offer_id":52550853001492,"sku":null,"price":2099.99,"currency_code":"USD","in_stock":true},{"title":"PAC 1207x .700\" Springs","offer_id":52550853034260,"sku":null,"price":2199.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1012\/8434\/8180\/files\/15LS3.1.jpg?v=1779913907"},{"product_id":"mangum-racing-brodix-267cc-ls3-cylinder-heads","title":"Mangum Racing Brodix 267cc LS3 Cylinder Heads","description":"\u003cp\u003e\u003cspan\u003eMangum Racing CNC Ported Brodix 15° LS3 Cylinder Heads\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003eBuilt from Brodix 6-bolt LS3 castings with extra deck thickness, our Mangum Racing 15° LS3 heads are designed for serious naturally aspirated and boosted combinations that demand airflow, strength, and repeatability.\u003c\/p\u003e\n\u003cp\u003eEach set is fully CNC ported in-house with brand new Centroid 5-axis CNC mills and Newen seat \u0026amp; guide machines. Every set of cylinder heads is hand blended and carefully inspected before final assembly to ensure dimensional accuracy and consistency.\u003c\/p\u003e\n\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003eAirflow Performance\u003c\/strong\u003e\u003c\/summary\u003e\u003cp\u003e(4.125” Bore Plate)\u003c\/p\u003e\n\u003cp\u003eIntake (Radius Entry)\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e.200” – 148 CFM\u003c\/li\u003e\n\u003cli\u003e.300” – 227 CFM\u003c\/li\u003e\n\u003cli\u003e.400” – 282 CFM\u003c\/li\u003e\n\u003cli\u003e.500” – 325 CFM\u003c\/li\u003e\n\u003cli\u003e.600” – 350 CFM\u003c\/li\u003e\n\u003cli\u003e.700” – 363 CFM\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eExhaust (No Pipe)\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e.200” – 114 CFM\u003c\/li\u003e\n\u003cli\u003e.300” – 164 CFM\u003c\/li\u003e\n\u003cli\u003e.400” – 200 CFM\u003c\/li\u003e\n\u003cli\u003e.500” – 233 CFM\u003c\/li\u003e\n\u003cli\u003e.600” – 240 CFM\u003c\/li\u003e\n\u003cli\u003e.700” – 243 CFM\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eWith a 267cc CNC intake runner and optimized 96cc exhaust port, these heads deliver strong mid-lift numbers with excellent high-lift stability, making them ideal for aggressive hydraulic roller street \u0026amp; race builds needing to retain the stock valve locations \u0026amp; angles.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003ePremium Hardware \u0026amp; Construction\u003c\/strong\u003e\u003c\/summary\u003e\u003cul\u003e\n\u003cli\u003e6-bolt Brodix LS3 casting with increased deck thickness\u003c\/li\u003e\n\u003cli\u003e15° valve angle, OEM LS3 valve spacing\u003c\/li\u003e\n\u003cli\u003e2.165” hollow stem stainless intake valves\u003c\/li\u003e\n\u003cli\u003e1.600” stainless exhaust valves\u003c\/li\u003e\n\u003cli\u003eBronze guides\u003c\/li\u003e\n\u003cli\u003ePAC .660” dual spring package\u003c\/li\u003e\n\u003cli\u003eTitanium retainers\u003c\/li\u003e\n\u003cli\u003eViton seals\u003c\/li\u003e\n\u003cli\u003e1.250” steel spring seats\u003c\/li\u003e\n\u003cli\u003e68.5cc CNC chambers (milling available at no charge)\u003c\/li\u003e\n\u003cli\u003eChamber softening options for 4.000”, 4.065”, and 4.125” bore sizes\u003c\/li\u003e\n\u003cli\u003e.006” per cc flat milling available\u003c\/li\u003e\n\u003cli\u003eMinimum bore: 4.000”\u003c\/li\u003e\n\u003c\/ul\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003eDesigned for Builders Who Care About the Details\u003c\/strong\u003e\u003c\/summary\u003e\u003cp\u003eThese are not mass-produced heads. Each set is machined, assembled, hand blended, and inspected in small batches to maintain strict quality control and dimensional consistency.\u003c\/p\u003e\n\u003cp\u003eExtra deck thickness adds durability for higher cylinder pressure combinations. The PAC .660” dual spring setup provides valvetrain stability for serious cam profiles. Stock pushrod length works in most applications but should always be verified based on camshaft and final milling.\u003c\/p\u003e\n\u003cp\u003eIf you’re building a combination needing to stay stock valve angles \u0026amp; locations then this cylinder head is hard to beat!\u003c\/p\u003e\u003c\/details\u003e","brand":"Mangum Racing","offers":[{"title":"TSP\/PAC .660\" Polished Springs","offer_id":52550854607124,"sku":null,"price":2699.99,"currency_code":"USD","in_stock":true},{"title":"PAC 1207x .700\" Springs","offer_id":52550854639892,"sku":null,"price":2799.99,"currency_code":"USD","in_stock":true},{"title":"PAC 1208x .750\" Springs","offer_id":52550863847700,"sku":null,"price":2799.99,"currency_code":"USD","in_stock":true},{"title":"PAC 1209x .750\" Springs","offer_id":52550863880468,"sku":null,"price":2849.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1012\/8434\/8180\/files\/BrodixLS3.1_a1bda0e1-3c39-4621-91fe-c791cca76a41.jpg?v=1779915175"},{"product_id":"mangum-racing-275cc-11-degree-ls3-cylinder-heads","title":"Mangum Racing 275cc 11 degree LS3 Cylinder Heads","description":"\u003cp\u003e\u003cspan\u003eMangum Racing CNC Ported MR275 11° LS3 Cylinder Heads\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003eBuilt 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.\u003c\/p\u003e\n\u003cp\u003eThis 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.\u003c\/p\u003e\n\u003cp\u003eEach set is fully CNC machined in-house on brand new Centroid 5-axis machining centers and finished on Newen seat \u0026amp; guide equipment. Every head is hand blended, inspected, and assembled in small batches to ensure repeatability and precision.\u003c\/p\u003e\n\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003eAirflow Performance\u003c\/strong\u003e\u003c\/summary\u003e\u003cp\u003eTested on a SuperFlow bench with a 4.125” bore plate\u003c\/p\u003e\n\u003cp\u003eIntake (Radius Entry)\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e.200” – 143 CFM\u003c\/li\u003e\n\u003cli\u003e.300” – 221 CFM\u003c\/li\u003e\n\u003cli\u003e.400” – 283 CFM\u003c\/li\u003e\n\u003cli\u003e.500” – 330 CFM\u003c\/li\u003e\n\u003cli\u003e.600” – 358 CFM\u003c\/li\u003e\n\u003cli\u003e.700” – 381 CFM\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eExhaust (No Pipe)\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e.200” – 112 CFM\u003c\/li\u003e\n\u003cli\u003e.300” – 161 CFM\u003c\/li\u003e\n\u003cli\u003e.400” – 202 CFM\u003c\/li\u003e\n\u003cli\u003e.500” – 232 CFM\u003c\/li\u003e\n\u003cli\u003e.600” – 242 CFM\u003c\/li\u003e\n\u003cli\u003e.700” – 248 CFM\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eWith 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.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003ePremium Hardware \u0026amp; Construction\u003c\/strong\u003e\u003c\/summary\u003e\u003cul\u003e\n\u003cli\u003e6-bolt Mangum Racing 11° LS3 casting with .750” deck thickness\u003c\/li\u003e\n\u003cli\u003eOptimized 11° valve angle and revised valve locations\u003c\/li\u003e\n\u003cli\u003e2.185” hollow stem stainless extended-length intake valves\u003c\/li\u003e\n\u003cli\u003e1.600” stainless extended-length exhaust valves\u003c\/li\u003e\n\u003cli\u003eBronze guides\u003c\/li\u003e\n\u003cli\u003eChoice of PAC 1207X, 1208X, or 1209X dual spring packages\u003c\/li\u003e\n\u003cli\u003eTitanium retainers\u003c\/li\u003e\n\u003cli\u003eViton seals\u003c\/li\u003e\n\u003cli\u003e1.250” steel spring seats\u003c\/li\u003e\n\u003cli\u003e70.5cc fully CNC chambers (milling available at no charge)\u003c\/li\u003e\n\u003cli\u003eChamber softening options for 4.000”, 4.065”, and 4.125” bore sizes\u003c\/li\u003e\n\u003cli\u003eFlat milling at .006” per cc\u003c\/li\u003e\n\u003cli\u003eSubstantial piston-to-valve clearance for advanced camshaft profiles and compression increases\u003c\/li\u003e\n\u003cli\u003eMinimum bore: 4.000”\u003c\/li\u003e\n\u003c\/ul\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003eBuilt for Maximum Effort Combinations\u003c\/strong\u003e\u003c\/summary\u003e\u003cp\u003eThe 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.\u003c\/p\u003e\n\u003cp\u003eThese 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.\u003c\/p\u003e\n\u003cp\u003eIf you are building a no-compromise LS3 combination, naturally aspirated or power-adder, the MR275 was designed for exactly that purpose.\u003c\/p\u003e\u003c\/details\u003e","brand":"Mangum Racing","offers":[{"title":"TSP\/PAC .660\" Polished Springs","offer_id":52550869090580,"sku":null,"price":2999.99,"currency_code":"USD","in_stock":true},{"title":"PAC 1207x .700\" Springs","offer_id":52550869123348,"sku":null,"price":3099.99,"currency_code":"USD","in_stock":true},{"title":"PAC 1208x .750\" Springs","offer_id":52550869156116,"sku":null,"price":3099.99,"currency_code":"USD","in_stock":true},{"title":"PAC 1209x .750\" Springs","offer_id":52550869188884,"sku":null,"price":3149.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1012\/8434\/8180\/files\/11LS3.1_ea8cb5b7-8950-4ee7-870e-e5baadae2c8e.jpg?v=1779915311"}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1012\/8434\/8180\/collections\/15LS3.3.jpg?v=1779914561","url":"https:\/\/mangumracing.com\/collections\/ls3-rectangle-port-cylinder-heads.oembed","provider":"Mangum Racing CNC Ported Cylinder Heads","version":"1.0","type":"link"}