This 2.5 special aluminum cylinder head is a race winning design for the four-cylinder Pontiac aluminum "Super Duty" that's proven itself in IMSA road racing and Competition Eliminator Series. This rugged, lightweight head gives you Pontiac and NASCAR quality with plenty of extra metal, and proven performance with totally redesigned, super free-flowing ports. Oversize ductile iron seats and phosphorus bronze guides are standard. Intake volume is 178cc. This head accepts standard four-cylinder intake port centerline manifolds.