Mangum Racing 275cc 11-Degree LS3 Cylinder Heads
The MR275 is a maximum-effort 11° LS3 cylinder head built around a Mangum Racing 6-bolt casting with a .750" deck surface. Revised valve locations, a 275cc CNC intake runner, and a 98cc exhaust port are engineered for airflow, piston-to-valve clearance, and durability in high-compression or high-cylinder-pressure combinations.
Key Features
- 6-bolt Mangum Racing 11° LS3 casting with .750" deck thickness
- Optimized valve locations with 275cc CNC intake ports and 98cc exhaust ports
- 70.5cc fully CNC-machined combustion chambers
- 2.185" hollow-stem stainless extended-length intake valves and 1.600" stainless extended-length exhaust valves
- Choice of PAC 1207X, 1208X, or 1209X dual springs with titanium retainers
- Bronze guides, Viton seals, 1.250" steel spring seats, and minimum 4.000" bore
Airflow Performance
SuperFlow data with a 4.125" bore plate; intake uses a radius entry and exhaust is tested without a pipe.
| Valve Lift | .200 | .300 | .400 | .500 | .600 | .700 |
|---|---|---|---|---|---|---|
| Intake CFM | 143 | 221 | 283 | 330 | 358 | 381 |
| Exhaust CFM | 112 | 161 | 202 | 232 | 242 | 248 |
Installation note: Extended-length valvetrain components require careful pushrod, rocker, and piston-to-valve clearance checks.
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