Air Flow Research LS1 Mongoose Cylinder Heads for Small-Bore 5.7L Engine CNC Ported 205cc w/ 66cc Chambers

Upgrade your 5.7L small-bore LS build with these cathedral-port cylinder heads (1510)! Built by Air Flow Research, this pair of LS1 Mongoose heads comes fully assembled with 66cc chambers. They’re highly versatile as you can use them for street, strip, and even towing applications. CNC porting then maximizes the valve’s airflow, giving you the power needed for high-RPM performance.

Features and Benefits:
- Fully assembled pair of 205cc cylinder heads with 66cc chambers
- Ideal for 5.7L (383 C.I.D.) engines operating at or below 6300 RPM
- Recommended for street, street/strip, and towing applications
- Made of A356 aluminum for strength, thermal stability, and reduced weight
- 100% CNC ported intake/exhaust runners and combustion chambers
- CNC porting maximizes airflow consistency and high-RPM performance
- Intake and exhaust ports are located in stock location
- Competition 5-angle valve job enhances airflow for high-RPM performance
- Uses PAC Racing hydraulic roller dual spring with 1.290" O.D.

205cc Flow Chart (CFM @ Valve Lift):
- .200” lift: 147 CFM intake, 111 CFM exhaust
- .300” lift: 214 CFM intake, 150 CFM exhaust
- .400” lift: 249 CFM intake, 209 CFM exhaust
- .500” lift: 284 CFM intake, 225 CFM exhaust
- .550” lift: 296 CFM intake, 230 CFM exhaust
- .600” lift: 301 CFM intake, 233 CFM exhaust

Specifications:
- Minimum bore diameter 3.900"
- Combustion chamber size: 66cc
- Valve angle: 15 degrees
- Port volume: 205cc intake / 84cc exhaust
- Intake port dimensions: 3.275" height x 1.120" width x 5/16” top and 3/8" bottom
- Exhaust port dimensions: 1.415" height x 1.710” width
- Intake valve: 8mm bead lock, 2.020" head diameter, 4.900" overall length
- Exhaust valve: 8mm bead lock, 1.600" head diameter, 4.900" overall length
- Seat pressure: 140 lbs.
- Maximum RPM: 6300-6500 RPM at less than 235-degree duration
- Chromoly retainers: 7-degree, 1.245" O.D., .885" I.D., and .655" inner step diameter
- Valve keepers: 7-degree bead lock
- Viton valve seals: .600" O.D. and .490" I.D.
- Hardened valve spring locator: 1.380" O.D. and .570" I.D.
- Valve spring pocket diameter: 1.510" O.D. 
- Maximum valve spring pocket machining: 1.525" O.D. 
- Deck thickness 0.750"
- Flat milling rate: .006" removed per 1cc reduction
- Maximum combustion chamber volume after milling: 58cc 
- Spark plug dimensions (with tapered seat): 14mm x .750"

Vehicle Fitment:
- 1960-1987 Chevy C10
- 1988-1998 Chevy/GMC C/K
*MUST be equipped with a 5.7L (383 C.I.D.) small-bore LS engine 

Please Note: Do NOT machine the spring pad any deeper.