AFR’s 270cc Big-Valve LS3 cylinder head is designed to move serious air where modern LS3/rectangle-port engines make power. The 2.200" intake valve increases curtain area and intake charge efficiency, supporting strong mid-range and sustained top-end. Designed around the 6-bolt option to enhanced head-gasket stability under elevated cylinder pressures that are ideal for high-boost and heavy nitrous, these same heads are also available in a 4-bolt configuration upon request for those straightforward fitments on traditional LS blocks and gaskets. Whether naturally aspirated or on the sauce, this head gives your LS3 the breathing capacity and sealing strategy to grow with your tune.

Basic Package Components
100% CNC Ported Combustion Chambers
100% CNC Ported Exhaust Ports
100% CNC Ported Intake Ports
Competition 5-angle Valve Job
Intake Valve 8mm LS3 Solid Stem 2.200 Intake , 5.200 OAL  7215 Exhaust Valve 8mm LS3 Solid Stem 1.570 Exh Valve, 5.205 OAL  7217 Spring Pacaloy Hydraulic Roller Spring 1.270 O.D., Premium Grade Chrome Silicon 8019 Retainer LS1 Titanium 7 degree Retainer 1.250 OD x .885 ID x .655 8512 Valve Lock LS1 7 degree Machined Hardened Steel Valve Locks - Stock Style Bead Lock 9007 Rocker Stud N/A N/A Guide Plate N/A N/A Valve Seal 8mm SBC, SBF, LS1 Viton Rubber Valve Stem Seal, .600 OD x .495 ID 6612 Spring Locator O.D. Spring Cup 1.380 OD x 1.300 ID x .570 ID (Fits 8017 &8019 spring) 8042 Intake Seat AFR SB Chevy & LS3 Intake Seat 2.200 OD x 1.750 ID x .375 9060 Exhaust Seat AFR SB Ford/LS1/LS3 Exhaust Seat 1.650 OD x 1.350 ID x .375 9069 Guide LS3 8mm Bronze Guide, .502 OD 9053 Rocker Support Rail LS3 Rocker Arm Rails 6040 Rocker Support Rail Lube LS3 Rocker Support Rail Lube#3 6041

 

270cc Large Bore Competition Flow Chart
	.200	.300	.400	.500	.600	.650	.700
Int	159	236	299	344	376	384	389
Exh	116	166	211	230	238	242	245

Test conducted at 28" of water (pressure) on Superflow 600
Bore Size: 4.155", intake 3/4" radius plate exhaust, 1 3/4" curved pipe
 

Specifications & Features:
Material	A356 Aluminum
Intake Port Volume	270cc
Intake Port Dimension	2.610"H x 1.300"W x 7/16° Radius
Intake Port Location	Stock
Exhaust Port Volume	93cc
Exhaust Port Dimension	1.540" H x 1.760" W
Exhaust Port Location	Stock
Combustion Chamber Size	69cc
Valve Cover Bolt Pattern	Center Bolt
Valve Angle	12°
Valve Spring Pocket Diameter	1.490" O.D
Max Valve Spring Pocket Machining	1.510" O.D
Warning: Do not machine spring pad any deeper.
Deck Thickness	.750"
Minimum Bore Diameter	4.000"
Flat Mill	.006" per cc 62cc Maximum
Minimum Cross Sectional Area	3.00 sq. in.
Spark Plug Dimensions	14mm x .750" w/ Tapered or Gasket Seat
Carb EO#

Recommended Components:
Intake Port Gasket	Factory GM or Aftermarket
Recommend Rockers - OEM w/ trunion upgrade Yella Terra 6733 w/ 5132 Valve Cover gasket.	Scorpion 1162
Exhaust Port Gasket	GM #12558573
Head Gasket	Cometic 4.160 Bore Size
Head Bolts (04+), ARP 134-3610	AFR #6334
Head Studs (04+), 2004 & Later Blocks ARP #234-4317, Pre 2004 Blocks ARP #234-4316	AFR #6335
Head Bolt Washers, Manley	AFR #6320
Suggested Manifold	FAST 92mm or 102mm
Spark Plug Starting Range	NGK TR55