Add to Favorite Sellers. Holley 12-847 Dominator Billet Carbureted By Pass Fuel Pressure Regulator. Hot Street/Race Carbureted Applications Two Port Adjustable from 4.5 to 9 PSI; Holley® Billet Fuel Pressure Regulators are part of a complete line of fuel system products from Holley®. They are precision machined from 6061-T6 billet aluminum for strength and durability. They feature a black bright dip anodized body and a clear bright dip anodized top for corrosion resistance and good looks. The Holley 12-847 fuel pressure regulator features (1) -10 AN O-ring inlet, (1) -10 AN O-ring outlet, (1) -8 AN O-ring return. Customer Service & Feedback. So we have a chance to make it right – we want your repeat business! Check out the official Holley Performance. For more great deals!!