Specifications for the cylinder head include combustion chamber volume: (A) 65cc / 72cc / 87cc; intake runner volume: 204cc; exhaust runner volume: 145cc; intake valve diameter: 2.
11"; valve stem diameter: 11/32"; exhaust valve diameter: 1.
66"; valve guides: manganese bronze; deck thickness: 5/8"; valve spring diameter: 1.
46"; 120lbs.
@ 1.
800" inst.
height; 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: stock; spark plug fitment: 14mm x 3/4 reach, gasket seat.
Performer Pontiac heads utilize a D-Port exhaust port configuration for standard D-port exhaust systems.
Designed for 1962-79 389, 400, 421, 455 cid V8 Pontiac engines with a 4.
060in.
or larger bore, they feature optimized oil return passages for increased oil flow.
Available in three heart-shaped combustion chamber sizes: 65cc, 72cc, and 87cc.
The 65cc combustion chambers are as-cast while the 72cc and 87cc chambers are fully CNCd to 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.
Cast with extra thick port walls and a compact port size, they are ideal for CNC and hand parting.
Complete heads include guide plates, rocker studs, and high-quality valve train for direct bolt-on application.
Head crossover is machined for 50-state emissions legal performance.
INSTALLATION NOTE: 350 c.
i.
d.
engines may require notching the block for valve clearance.
Three head bolt bosses are raised higher than standard D-port heights and will require head bolt kit #8561 for installation.
Deck thickness: 5/8", rocker stud diameter: 7/16", pushrod diameter: 5/16" (width of slot in guide plate).
