Splayed-Valve Aluminum Cylinder Head


  • Extremely aggressive, all-out competition head
  • 240cc “as-cast” intake ports
  • 78cc “as-cast” exhaust ports
  • 45cc “as-cast” combustion chambers


Semi-Machined Splayed Valve Aluminum Cylinder Head

P/N 24502517

– Semi-machined aluminum race head
– 240cc “as-cast” intake ports
– 78cc “as-cast” exhaust ports
– 45cc “as-cast” combustion chambers
– Same casting as P/N 12480146

Aluminum Splayed Valve Race Head Technical Notes:

– Made of 355-T7 aluminum
– No valve seats or guides provided
– Extra-thick decks for angle milling or heavy flat milling
– Extra port material (0.240″) for professional porting
– Completely revised intake and exhaust ports provide ultimate airflow potential
– 45cc “as-cast” combustion chambers
– Modified valve angles (16° x 4° intake, and 11° x 4° exhaust)
– Designed for longer-than-stock 2.200″ and 1.650″ valves
– Valve spring pads accommodate 1.625″ diameter springs
– Revised location angled spark plugs (14mm, 5/8″ hex, 3/4″ reach, gasketed plugs)
– Designed for aftermarket shaft-mount rocker systems
– Custom-fabricated intake manifold required
– P/N 10185042 intake manifold gasket required
– Valve cover gaskets P/N 10185043 required


Splayed-Valve Aluminum Cylinder Head

24502517 Chevrolet Cylinder Head


Chevrolet Performance Splayed Valve Aluminum Race Cylinder Heads are extremely aggressive, all-out competition heads and not intended for street use. Splayed valves point both intake and exhaust valves at the center of the cylinder bore. As the valves open, they move away from the edges of the bore. That allows maximum-size valves to be installed without increasing bore size. The result is dramatically increased airflow, compared to inline-valve-design cylinder heads.

GM engineers have designed the castings to have a 0.240-inch minimum port wall thickness, which leaves ample room for extensive custom porting. Intake valves are angled 16-degrees to the deck surface and splayed 4-degrees. Exhaust valve angles are 11-degrees with a 4-degree splay. Making more than 1000 naturally aspirated horsepower with these cylinder heads is easily achievable.

Prop65WARNING: These auto parts can expose you to chemicals including phthalates and lead. Installing or using these parts can expose you to other parts containing these chemicals and to engine exhaust, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to