Uses aftermarket GX390 style large-port casting. Heads are ported, bead blasted, flowed, and milled. Heads can be fitted with either single or dual springs. Single springs are recommended for 306 and smaller cams; dual springs are recommended for 307 and larger cams. 

Choose a 36 or 40mm Intake Valve, comes with 32mm Exhaust Valve.

Increased milling can increase compression, but at the expense of reliability. ** .120 Not Recommended.

Product Includes:

• Ported & Bead Blasted Head, Milled to Specs
  
• Oversize Stainless Intake & Exhaust Valves
  
• Aluminum or Titanium Retainers
  
• Split Keepers
  
• HD Single or Dual Springs
  
• Valve Spring Shims
  
• 3-Angle Valve Job