There are several important reasons why World’s S/R cylinder heads are the preferred alternative to expensive OEM castings or junkyard rebuilds First, you should know these heads are designed with extra-thick decks and walls for improved reliability as well as equipped with hardened steel exhaust seats that are compatible with today’s unleaded gasolines. They also come with screw-in rocker arm studs for extra durability. Needless to say, the S/R is substantially more durable than OEM castings Secondly, they are fully 50-state emissions legal and because they are an OEM replacement head, they are legal for use by many oval tracks and race Sanctioning organizations Valve cover rails have been raised and carefully machined to eliminate oil leaks and the heads can accommodate either early style perimeter or late model center bolt valve covers.

Marine applications are also available too!
Designed for use as replacements for MerCruiser engines based on the small block Chevy, these heads are built to operate at higher temperatures than standard automotive heads and feature Manley inconel exhaust valves and stainless steel intake valves for superior reliability.

Casting ID Number: I-052, I-058
Material: High density cast iron
Valve Seats: Intake (integral), exhaust (hardened)
Valve Guides: Integral cast iron
Spring Seats: Machined for 1.560" and 1.250"
Valves: Manley stainless steel valves in assemblies (inconel exhaust valves on marine applications)
Valve Diameter: 2.020" intake, 1.600" exhaust (11/32" stem)
Rocker Arm Studs: Screw-in style
Rocker Arms: 1.5 ratio (use of 1.6 ratio will require elongation of pushrod holes)
Intake Runner: 170cc, standard port location
Exhaust Ports: 65cc, standard location
Combustion Chamber: 58cc, 67cc or 76cc, straight plug orientation
Spark Plug: 14mm 5/8" .460" reach tapered style
Valve Job: Multi-angle intake and radiused exhaust
Valve Cover Rail: Raised w/ perimeter and center bolt pattern
Valve Angle: Stock 23°
Accessory Bolt Holes: Stock
50-State Emissions legal
Accepted by most oval tracks and sanctions as stock replacements. Check with rule book.

Spring Specs
1.250": 100 lbs. @ 1.810", 300 lbs. @ 1.250", coil bind @ 1.200", max lift @ .560"
1.437": 125 lbs. @ 1.810", 340 lbs. @ 1.210", coil bind @ 1.160", max lift @ .560"

Head Flow @ .500 Lift
220 intake, 151 exhaust (Super Flow 1050)
232 intake, 161 exhaust (Super Flow 600)
All heads flowed with a standard .750" intake plate, without exhaust tube, and 28" of water.