{"id":996,"date":"2026-08-06T12:40:31","date_gmt":"2026-08-06T12:40:31","guid":{"rendered":"https:\/\/thetorquefactory.com\/?post_type=product&p=996"},"modified":"2026-08-06T12:40:31","modified_gmt":"2026-08-06T12:40:31","slug":"fms-motorsport-om604-manifold-flange","status":"publish","type":"product","link":"https:\/\/thetorquefactory.com\/index.php\/product\/fms-motorsport-om604-manifold-flange\/","title":{"rendered":"FMS Motorsport OM604 Manifold Flange"},"content":{"rendered":"

This FMS Motorsport OM604 manifold flange is the CNC-machined billet head flange used in our OM604 turbo manifold kit, sold separately for anyone building their own manifold or replacing a damaged flange. It’s designed in-house and machined from a solid billet of stainless steel \u2014 not adapted from a cast manifold, where casting is a built-in compromise between quality, performance, and price. This is a high-performance engineered component, and it’s priced and built accordingly.<\/p>\n

Why the Port Transition Actually Matters<\/strong><\/p>\n

A flange with a poor transition between the head’s low, wide exhaust ports and round tubing creates turbulence and restriction right at the source \u2014 before the exhaust gas has even left the head. That shows up two ways: slower turbo spool, because the pressure pulse driving the turbine loses energy fighting through a bad transition, and more heat trapped in the head, because the gas takes longer to evacuate the port. A properly machined transition does the opposite \u2014 cleaner flow means faster spool, more usable power, and a head that runs cooler under sustained load. That’s the difference between a part that’s just there to bolt something together and one built for reliable performance.<\/p>\n

Why It’s 25mm Thick<\/strong><\/p>\n

The OM604’s exhaust ports are low and wide, a shape that doesn’t transition cleanly into round tubing without real material to work with. Machining a smooth, gradual change from that port shape into a round tube takes enough thickness to shape the transition properly, rather than leaving a sharp step where the port meets the tube. That’s the actual reason for the 25mm.<\/p>\n

CNC Billet, Not Cast<\/strong><\/p>\n

Cast manifolds are cheap to produce at volume, but casting is a compromise \u2014 it can’t hold the same tolerances as machining, and the internal geometry is whatever the mold allows, not what the flow actually needs. This flange is CAD-designed in-house and CNC-machined from a solid billet of stainless steel, so every port transition is exactly what we designed it to be.<\/p>\n

Fitment<\/strong><\/p>\n

The port spacing is identical across OM604, OM605, and OM606 \u2014 it’s the same pitch repeated once per additional cylinder. What differs is the number of ports and the overall length of the flange: the OM604 is a 4-cylinder head, shorter than the OM605 and OM606. Each flange is machined to match its own engine’s length and port count, so they are not interchangeable<\/strong> between engines \u2014 make sure you’re ordering the OM604 version specifically.<\/p>\n

Build Your Own Manifold<\/strong><\/p>\n

Sold separately from the turbine end, so you’re free to run your own choice of turbine flange \u2014 single-entry T3, divided T3\/T4, or your own spec. If you already own our OM604 kit and need a replacement flange, this is the same part.<\/p>\n

Specifications<\/strong><\/p>\n