The RBC intake manifold is widely known as one of the best bang for your buck K Series intake manifolds that money can buy. The 2 problems with the RBC are that it does not fit on most K series engines due to its built in water passage and it has a small throttle body opening (64mm).
Our solution to this problem is a process called "clipping and porting."
First we start by removing the coolant port by inserting a large screwdriver or pry bar into the end and then giving it a good twist back and forth until it comes out.
We then lay a K20A2 intake manifold gasket onto the flange surface of the intake manifold and trace a line then remove the water passage portion of the RBC using a grinder disc. This ain't pretty, but we will work on that next.
We use the sanding disc to smooth out the rough angles that were created by the cut off wheel.
Now the RBC is clipped and ready to install onto any K series cylinder head, however, we take it a step further and port match the throttle body opening to whatever size throttle body the kit comes with if you select that option at checkout. For the sake of this blog post, we will be port matching to a 70mm throttle body.
First we install a 70mm throttle body adapter so that we can trace the 70mm throttle body size onto the flange of the manifold. To be clear, we are only using the 70mm throttle body adapter as a tool during this process. We would never trace sharpie onto a product that we intend to ship to a customer.
We then use the tungsten carbide burr shown in the image below to evenly and smoothly open up the throttle body opening to the 70mm size. Having done this process hundreds of times, we take our time and really blend the new opening into the intake manifold plenum. Our goal is to have a smooth transition as the air flows into the plenum.
The overall shape is looking great, but the finish is looking really unrefined. To really take this job to the next level, we swap out to a sanding bit on the end of the die grinder to really smooth out the opening which results in a finish that is smoother than the OEM casting.
Lastly, we bolt the 70mm throttle body adapter back up to check our work and dang that's looking mint.
This RBC intake manifold is ready to make great power on any K series engine. If you are looking to take your K series car to the next level with a clipped and ported RBC intake manifold, feel free to browse our selectin of RBC kits offered on the site, or use our live chat feature to ask any questions you may have about this upgrade.
Note: This upgrade can be used on your 8th gen Civic Si if you prefer to run an Intake Manifold Adapter (IMA). This allows you to remove the intake manifold without having to drain the coolant.