Engineered to greatly increase performance and efficiency, Edelbrock E-Tec heads fit 302, 327, 350 and 400 c.i.d. small-block Chevys with Vortec-style intake manifolds. They incorporate Edelbrock's new high-quench combustion chamber which promotes a more uniform atomization of the air/fuel mixture for more power. Spark plugs have been positioned closer to the center of the cylinder for more efficient combustion. Edelbrock E-Tec heads come with one-piece stainless steel valves that are swirl-polished and have undercut stems for maximum flow. They accept center-bolt or standard valve covers, work with most stock exhaust manifolds and have Vortec-style intake ports. Exhaust port exits are .200 higher than standard heads. For maximum performance, match with an Edelbrock Vortec manifold.The E-Tec 170 heads feature 170cc Vortec-shaped intake and 70cc exhaust ports. They flow 20% more on the exhaust side than the cast iron Vortec heads and produce power up to 6000 rpm. The 64cc combustion chamber will result in approximately 9:5:1 compression when used with stock pistons in 350-inch engines. E-Tec 170 heads come with 1.94-inch intake and 1.55-inch exhaust valves. 50-state street legal.