These heads use the popular Pontiac D-Port exhaust port exits for use with standard D-port aftermarket exhaust systems. Performer Pontiac heads are designed for 1962-79 389, 400, 421, 428 and 455 cid V8 Pontiac engines with a 4.060" or larger bore. Manufactured with optimized oil return passages for improved flow. Will accept factory pushrod guideplates (must split guideplate pairs), rocker studs and accessory bosses. The casting is manufactured from A356 aluminium and heat treated to T6 spec for superior quality. These heads are available in three dual quench combustion chamber sizes, including 65cc, 72cc, and 87cc; the 72cc combustion chambers provide a 9.5:1 compression ratio when used with flat-top pistons. The spark plug has been relocated closer to the exhaust valve for improved performance. These heads are cast with extra thick port walls and a compact port size, making them ideal for CNC & hand porting. Heat crossover is machined for 50-state emissions legal performance.

Combustion chamber volume: 72cc
Intake runner volume: 195cc
Exhaust runner volume: 145cc
Intake valve diameter: 2.11"
Exhaust valve diameter: 1.66"
Valve stem diameter: 11/32"
Valve guides: Manganese bronze
Deck thickness: 5/8"
Valve spring diameter: 1.46"; 120lbs. @ 1.80" Installed Ht.
Valve spring maximum lift:.550"; 1.150" Coil bind
Rocker stud: 7/16"
Guideplate: Hardened Steel
Pushrod diameter: 5/16"
Valve Angle: 14°
Exhaust port location: D-Port Stock location
Spark plug fitment: 14mm x 3/4" reach, gasket seat
Made In: USA