ProMaxx 3151A XXtreme 255 LS1/LS2 Cathedral 4.00+ Large Bore 63cc Hydraulic Roller .650 Heads

Fits Vehicle:LS1/LS2 Cathedral Port 4.00+ Large Bore

SKU: 3151A

The XXTREME LS 255 cathedral port head utilizes an 11-degree valve angle to push it to the front of all cathedral aftermarket cylinder heads. Size for size, no one can touch this bad boy. If you have a 4.00 inch plus bore size engine and need cathedral heads, look no further to push your power to the XXTREME.

Features:

• LS 255cc Extreme Cathedral Large Bore 4.00+ min 2.125/1.60 63cc .650 Tool Steel Associated Springs Pair
• Requires 4″ bore minimum and LS3 intake rocker
• Pro-designed ports & chambers
• 255cc as-cast port designed and tested in the USA
• Ultra-smooth 356-T6 Aluminum Casting
• 5-angle valve job
• 63CC or 59CC Chamber size or additional options available
• 11 Degree Valve Angle
• Diamond honed guides
• Built-in raised valve cover rail
• Monster .750 deck thickness
• Billet LS3 OEM Rocker Stand
• For use with standard or 6 bolt pattern
• Large spring pockets
• Utilizes 2.125 intake valve and 1.60 exhaust valve (Larger sizes available upon request)
• Multiple spring options
• Assemblies include: 21-4N stainless 1pc swirl polished back cut valves
• Machined and Assembled in the USA
• Outperforms other comparable heads in the industry
• Accessory brackets may require different bolts
• Sold in Pairs

Flow Chart

2.125/1.60

Cylinder Head Options

Technical Specs

Combustion Chamber ……53cc-66cc
Weight …………………………66 lbs.
Intake Runner ……………. 255cc
Exhaust Runner …………..
Intake Valve Size …………2.125”-2.200″
Exhaust Valve Size …….. 1.57″-1.60””
Spring Pressure

Hydraulic Roller .650 max lift

Closed …………………… 155 lbs. @ 1.800”-
Open …………………….. 425 lbs. @ 1.150”

Valve Guide ……………Manganese Bronze
Valve Seal Material … Viton
Retainer Material ……Titanium or Tool Steel
Valve Job ……………… 5-angle
Valve Spacing ………. OEM LS3
Valve Seats ……………Hardened Steel

Spark Plug…………….NGK R5671A-7 3/4 GASKET SEAT PLUG