03-28-2012, 03:04 AM. Holley 12-804 Carburetor Fuel Pressure Regulator 1 To 4 PSI Bottom Is Inlet Sides Are Outlets for a sandrail, rock Crawler, KOH, Ultra4, truck, UTV, side-by-side, dune buggy, mini buggy, manx, king of the hammers, 4x4, or Jeep. Recommended Parts. Inlet from fuel pump is at bottom. If I wait a hour for the system to cool to ambient temperature then it starts easy. Holley recommends applying PTFE paste to the NPT thread of the fittings before installation on these applications. All Holley regulators are pre-set at the factory at 2.8 PSI so there is no guesswork when first installing the regulator. By 1913 it was the other way around. Holley Fuel Pressure Regulator Rebuild 12-804 - YouTube 0:00 / 37:53 Holley Fuel Pressure Regulator Rebuild 12-804 DurocShark 309 subscribers Subscribe 10K views 3 years ago I walk through. [endif]--> Many thanks for taking the time to clarify this interesting subject .