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PORTS AND FITTINGS
The fuel rail ports are tapped for 8AN ORB.
8AN ORB Adapter Fittings can be found HERE.
8AN ORB Fuel Pulse Dampers can be found HERE.
Fuel Pressure Gauge Adapters can be found HERE.
Appropriate fittings must be selected based on the specific application. Ample space around the fuel rail port(s) is necessary for larger accessories such as fuel pressure regulators, fuel pressure gauges, and fuel pulse dampers. To verify clearance, the dimensional drawings on the product pages can be used as a reference guide.
These Radium Engineering fuel rails are compatible with the VR38DETT engine found in the Nissan R35 GT-R. They are machined from 6061 aluminum and anodized black for compatibility with all popular fuel types including E85. Manufactured with a large internal bore, the fuel rail can support all necessary engine power requirements. Each rail has four 8AN ORB ports (2 end ports and 2 top ports for a total of 8 ports). 
The fuel rails mount with insulating spacers and washers for 100% fuel insulation from the hot intake manifold. The unique lower intake manifold mounting points permit shorter less restrictive rails. Additionally, the OEM injector clips can be reused, as shown below.
With 4 ports on each rail (8 total), it is easy to add fuel system accessories such as a pressure transducer, fuel pulse dampers, etc. There is also opportunity to plumb the fuel rails in parallel or series.
As shown below, the base kit (P/N: 20-0556-02) includes ONLY the fuel rails and associated mounting hardware. NO FITTINGS ARE INCLUDED.
FUEL INJECTOR COMPATIBILITY
This fuel rail is compatible with factory or OEM equivalent fuel injectors. If upgrading fuel injectors, consult your aftermarket injector supplier for details. Radium Engineering cannot specify any further injector dimensions other than stating ‘OEM equivalent’.
PLUMBING KIT
20-0956-PK Fuel Rail Plumbing, Nissan R35 GT-R
When used with the 20-0556-02 fuel rails, this kit permits a bolt-on, plug and play affair. A stainless steel mount if provided for the Radium FPR. Low profile 90 degree SAE adapters with PTFE fuel hoses connect the OEM hard fuel lines to the FPR. PTFE fuel lines run from the FPR to the rear fuel rail ports. Two Radium fuel pulse dampers and a pressure gauge are included and all necessary adapter fittings. 
RA-series regulators feature the first tool-less pressure adjustment. A jam nut and set screw are no longer required. With a simple turn of the knob, pressure will be increased or decreased. To aid in adjusting pressure, there are incremental detents that provide haptic feedback to the user. Every detent permits 1psi (+/-0.5psi) of adjustment depending on current fuel pressure.
RA-series regulators feature a 360 degree swiveling vacuum reference port that is double O-ring sealed. This is the first in the industry. It permits the installer to quickly point the vacuum fitting in any direction with no tools required.
There are 4 interchangeable 10-32 threaded vacuum port fittings provided to cover all scenarios.
1. Barbed Fitting: A black zinc-plated 3/16" (5mm) barb machined from high strength steel that is compatible with the following vacuum hoses: 5/32" (4mm), 3/16" (5mm), and 7/32" (6mm).
2. 3AN Male Fitting: A black zinc-plated adapter machined from high strength steel that is compatible with 3AN hose ends.
3. Push-To-Connect: A nickel-plated brass fitting with Buna-N O-rings that is compatible with hard plastic 1/4" OD tubing.
4. Vacuum Plug: A black oxide stainless steel screw that is used to maintain a constant (non dynamic) fuel pressure.
This kit is suitable with all gasoline types including unleaded, leaded, oxygenated, and pre-mixes. Furthermore, it is compatible with alcohol blends of fuel including methanol, ethanol, and E85.
OEM FPD ADAPTER
20-0459 FPD Adapter, 8AN ORB, 27mm Bore
The OEM VR38DETT fuel pulse damper can be reused with this adapter. These can install into any fuel rail port provided there is adequate clearance.
NOTE: If the 20-0956-PK plumbing kit (listed above) was purchased, this adapter can be used in the spare top port, as shown below.