K SWAP GUIDE (part one) RBC/RRC manifold, Throttle body tech, K-tuned adjustable EP3 pulley

For the first installment of this multi-part K-swap guide, I’ll be covering how to fit an RBC/RRC manifold and install a K-Tuned adjustable EP3 pulley. I know that may not sound like much, but trust me—there are some important details, tips, and tricks to make your life a bit easier. If you’re tackling a K-swap, I highly recommend going with an RBC intake manifold. Not only does it look 100 times better than the stock PRC/PRB K20 manifold, but it can also provide some noticeable horsepower gains, even on a stock motor. You can read more about this in Super Street’s K-series intake manifold shootout by clicking the link below.

http://www.superstreetonline.com/how-to/engine/sstp-1002-k-series-intake-manifold-shootout

Now, that article may be a bit dated by today’s standards, as there are some great manifold options available now. However, for a stock or mildly built K20, the RBC still offers the best bang for your buck. Used RBC manifolds can be found for $100-150, while new ones typically run around $250. Of course, the RRC manifold (the more expensive option) can produce impressive power gains, but its high cost becomes less justifiable when you could get a ported RBC manifold, which performs just as well for a similar price.

That being said, I personally run an RRC on my K20. The RRC is 100% bolt-on, OEM, and worry-free, meaning I don’t have to second-guess whether a ported RBC could have been better—or if the porting job wasn’t done properly and could have cost me power.

For me, the K-Tuned EP3 adjustable pulley is the easiest and most cost-effective solution compared to the relocation kit. You’ll need either of these kits if you’re deleting power steering— which, in most cases, you should be. The “universal A/C & P/S eliminator kit” requires swapping the pulley on the alternator itself and places the alternator lower in a hard-to-access/service location.

This is strictly my personal opinion, and I’ve used the EP3 adjustable pulley on two separate K20 swaps without any issues. However, Pat has experienced a bearing failure on the pulley before, which seems somewhat common among fellow track enthusiasts. That said, I can’t be certain if this was due to improper belt tension or adjustment during installation, as I’ve had mine for longer without any issues.

If you do encounter bearing issues, there’s an easy fix—just replace the bearing at your local auto parts store. Since the EP3 kit has only one moving part, there’s less risk of failure compared to the A/C & P/S eliminator kit.

Let’s install an RBC/RRC intake manifold! The first step is to remove the stock PRC/PRB intake manifold. This will give you the necessary clearance to test-fit the RBC/RRC manifold during the cutting and grinding process.

As you can see, the intake manifold won’t come off completely due to the water pump, PCV, and belt tensioner unit being in the way. You’ll need to create some space—there’s no way it will come off without doing so.

To create space, start by removing the three 12mm bolts holding the alternator in place. Then, loosen the four 14mm bolts (one of which is a nut) securing the entire assembly to the block. You don’t need to fully remove these bolts—just loosen them enough to allow the unit to shift away from the block by about 1/2 to 3/4 inch.

Next, use a pry bar to carefully leverage the assembly about 1/2 inch away from the block to create enough space for the manifold to come off. Be gentle when prying, and make sure to pay attention to what you’re prying on to avoid any damage.

Above, you can see that only a small amount of clearance was needed. Now, simply bolt the four bolts (one of which is a nut) back down evenly, and you’re all set. As shown above, there are two studs that protrude from the head, which are the reason the manifold couldn’t be removed easily. If you’ve made it this far, you’re likely already aware of this.

Pro tip: Remove these two studs and use bolts to attach the intake manifold instead. This will make future removal much easier, as you won’t need to disassemble all that other stuff.

I’ll use the double-nut trick to remove the studs. I don’t have a stud remover, though that would definitely make life a bit easier.

1. Take two nuts and screw them onto the stud, back-to-back.
2. Use two wrenches to tighten the nuts against each other as firmly as possible.
3. Next, use the wrench closest to the head of the stud to turn it counterclockwise. This will loosen the stud.
4. Once the stud is loosened, use the two wrenches to slightly loosen the nuts from each other—just enough to spin the stud off completely. Keep them snug enough that they don’t slip while turning, but not so tight that it becomes difficult to separate the nuts once the stud is fully removed.

Do this for both studs, and you should now have no studs protruding from the head.

Now that you’ve removed the stock PRC manifold, let’s install the RBC/RRC intake manifold.

So, of course, Pat decided to go with a brand-new RBC manifold from Honda. Honestly, it’s only about $100 more than a used one. To save yourself the headache of dealing with people selling faulty items, risking scams, or just for the convenience of having it shipped directly to your door, it’s often the better option. That said, I’ve bought used ones before without any issues—you just have to know what to look for.

When buying a used manifold:

• Threaded Holes: Ensure none of the threaded holes are stripped. Bring a few bolts of the correct sizes, and thread them into each hole to check for smooth operation without resistance or hard spots.
• Throttle Body Holes: Check the holes where the throttle body bolts up. Sometimes, people use bolts that are too long, which can crack the manifold or cause a vacuum leak.
• Cut Manifolds: Avoid manifolds that have already been cut unless they come from a reputable source. A poorly executed cut can ruin the fit or function.
• Shaved Manifolds: Be cautious when buying a used manifold that has been shaved, as you may need to use the shaved holes depending on your setup.

Other than that, it’s just a cast piece of aluminum designed to deliver air to the engine. There are no moving parts to wear out, so as long as the above checks are good, a used manifold can be a reliable option.

To fit an RBC/RRC manifold on a K20A/A2/Z1 head, you’ll need to cut off the water neck section. The pictures below illustrate the difference between Pat’s old K20A RBC Euro R motor (TSX/Accord) and the new JDM DC5 PRC/PRB K20A Type R motor.

Above, you can see how the PRB head (with the red valve cover) has the upper coolant outlet located on the front of the head, whereas the RBC head (with the teal valve cover) has the upper coolant outlet positioned on the side of the head.

Above, you can see how the stock PRC intake manifold is separate from the upper coolant outlet.

Below, the differences between the two manifolds are shown stacked on top of each other. This provides a clear idea of which section of the RBC/RRC manifold needs to be cut off to make it fit.

Here’s what you’ll need to prepare before cutting.

• A really long extension (or something similar).
• RBC/RRC manifold.
• Marker.
• OEM intake manifold gasket.

Take note: The gasket only fits one way. Below, I’ve intentionally placed it the wrong way for reference. You can see two of the holes don’t line up (the finger is pointing to one).

Below, I’ve flipped it, and now you can see that all the holes on the gasket align with the manifold. (Refer to the finger pointing to one of the holes).

I simply slide four bolts in to align the gasket and keep it from falling off.

Once I’m ready to begin marking what I need to cut, I use two fingers to center the gasket (you’ll be able to feel when it’s even).

Take your marker and trace along the edge of the gasket. Note: You are using the OEM PRC gasket that came off the K20A/A2/Z1 head, as this is the one you’re making the manifold fit onto.

What you’re left with is a guide of where you need to make your cuts.

Next, we’ll move the water neck out of the way. A pro tip: the water neck is made of steel and will be much harder to cut compared to the aluminum of the manifold. It can also obstruct the cutting process.

Take your long extension (or anything that will fit in the water neck hole). The longer, the better. You’ll rotate the water neck out of the way 180 degrees, which will provide more clearance for cutting. Don’t worry about damaging the water neck, as you won’t be using it since it’ll be cut off.

Make a straight cut to remove the main section from the manifold. Don’t stress about following the curved line exactly; you can use a flap wheel to carve out the desired shape more precisely.

Be cautious while cutting to avoid accidentally cutting through any essential components on the backside. Ensure you properly plan your cut and the path you’ll take before turning on the cutoff wheel. The reason I turned the water neck in the opposite direction becomes clearer now.

Now, take a flappy wheel and grind away the curved areas so that it fits properly around the water neck on the head.

You can now see it beginning to take shape.

Above is what you should end up with. Take your time when doing this. If you scuff, mark, or damage any part of the mating surface, you are most likely going to have a vacuum leak. PAY ATTENTION to how much you are removing. You can test fit it as many times as you need, so there is no need to grind it all off in one session.

Most people would be too scared to try this, but it’s actually quite manageable. The preparation is the most important part, and visualizing where your cuts will go before making them is key to success.

Once everything is cut and ground down, make sure you blow it out thoroughly with an air compressor and/or spray liberally with brake cleaner. You don’t want any metal shavings contaminating your engine.

It’s a tight fit, so take your time and grind away little bits at a time while frequently test fitting.

I’m sure you’ve already noticed the thermal intake manifold gasket installed, but here’s a picture of the necessary parts to complete the manifold swap. (Please disregard the Spoon drain plugs; we’ll cover those in another part of the series).

So, a PRC/PRB K20A, A2, or Z1 throttle body won’t bolt directly to an RBC/RRC manifold. Several companies, like Karcepts, K-Tuned, and Hybrid Racing, offer adapter kits to make this fit possible. Avoid cheap or knock-off versions, as they often result in vacuum leaks and other issues.

Some argue that thermal intake manifold gaskets are too thick and may prevent bolts/nuts from tightening properly, leading to potential loosening over time. However, I’ve had mine installed on a K20 for 5 years without any issues. As you can see in the picture below, there’s plenty of thread engagement, and the bolt has remained secure without any vibration or loosening.

The K-Tuned TB adapter features a removable ring, allowing you to switch between a stock TB or a ported/larger TB without the need to modify or port the adapter itself.

It’s also worth noting that the kit includes a gasket for the adapter to the manifold, but not one for the throttle body to the adapter. For this, you’ll need to order a gasket designed for the PRC/PRB intake manifold (since that’s the type of throttle body you’re using).

This is what it looks like once everything is installed. When bolting the manifold on, make sure to use all bolts of the same length. You’ll be short two bolts since they were studs before you removed them, so ensure you match two other bolts to the original ones that held the manifold in place.

On top of the throttle body, there’s a sensor you’ll no longer need: the purge control solenoid. It’s the one directly on top of the TB with the bronze metal around it. Simply loosen the Phillips screw holding it in, then twist and pull to remove it. Sometimes, a rubber grommet can make it difficult to remove, but just keep twisting and pulling until it comes off.

In your K-Tuned TB adapter kit, there’s a rubber plug included that you’ll insert into the existing hole to prevent any vacuum leaks.

Pro tip: Spray some WD-40 on the rubber plug to help it slide in more easily. The WD-40 will evaporate by the time you start the car, ensuring a secure fit.

It may not go in completely, so don’t worry. I’m sure you also noticed that I removed the throttle cable bracket and the other vacuum line bracket. These won’t be reused, and you’ll need to source a throttle cable bracket designed for a K-swap setup. We’ll cover that in the next installment of the series. Additionally, you’ll need to block off the hole on the new RBC/RRC manifold where the MAP sensor would go. K-Tuned offers a useful block-off plug for this purpose.

Now, let’s move on to the IACV (Idle Air Control Valve). You have two options here:

1. You can remove it and install a block-off plate, but you’ll need a Hondata or another programmable ECU to disable the sensor so it doesn’t trigger a check engine light.
2. Alternatively, you can leave it plugged in. I’ve chosen to keep mine plugged in on my car, while Pat opted to block his off and disable the sensor in KPro. There’s no functional difference between the two setups, only a matter of aesthetics.

So here is the IACV…

The Idle Air Control Valve (IACV) is often the main culprit behind a surging idle, especially after a swap. Exposure to salty air can cause oxidation, leading to clogs or blockages that impair the IACV’s proper function. A while back, I wrote a HOW TO: Clean the IACV article, which goes into detail on how to address this issue. You can read more about it by clicking the link below:

How to clean K20 Idle Air Control Valve (IACV)

See more

Patrick chose not to run an IACV; instead, he used the Karcepts block-off plate on his old motor.

Below are some pictures showing a gunked-up IACV (the one I just removed from his new motor).

The mechanism inside is what needs to spin freely. Oxidation often prevents it from functioning properly, leading to dreaded idle surges. For a detailed guide on disassembling and cleaning the IACV, click the link above.

If you choose to keep the IACV bolted on after cleaning, simply block off the two nipples with rubber caps.

But of course, Pat is not keeping his.

Be sure to remove ALL the old gasket material. Spending the time here is crucial to avoid troubleshooting a vacuum leak later once the car is running.

I simply use a razor blade to carefully remove the old gasket.

Then clean the rest of it off with a Scotch-Brite pad.

Remember you need a new OEM PRC/PRB TB gasket. Now bolt your TB on.

Looks much cleaner without all the accessories on it.

Next, we’ll remove the idle air control valve thermostatic switch. It’s not needed, as the car will run just fine without it, and removing it won’t trigger a Check Engine Light (CEL). I’ve personally run a bone stock ECU without any issues or CELs.

I break off the nipple coming out of the side of the air assist valve. This allows you to fully rotate the valve without needing to remove the valve cover. The plastic is brittle, so I tap it gently with a solid object, and it snaps off easily.

Now take a 22mm wrench/socket and remove.

You’ll now be left with a hole. If this hole isn’t sealed, it will spew coolant once the engine is running. Block-off plugs are available from various companies, and it’s common to install a coolant temperature sensor there to ensure your cluster displays a working temperature gauge. Pat previously had one on his old motor, so I simply transferred it over.

I applied some Hondabond to the threads to ensure a complete seal. You could use Teflon tape, but coolant can eventually degrade the tape, potentially causing leaks. The plug doesn’t need to be fully threaded; you’ll feel when it’s “tight.” DO NOT over-tighten!

Next, you will need to block off the smaller water nipple.

slide a rubber cap over it.

Then use a small hose clamp to secure it. Since it’s part of the coolant system, it will become pressurized, and without a clamp, the rubber cap could blow off under pressure. There may be a better way to handle this, such as welding it shut, but this method has worked perfectly for my K-swap over the past 5 years, including plenty of track time, with no issues.

Lastly, there is a nipple emerging from the center of the intake manifold where the air idle assist hose would connect. It is not necessary to cap this nipple since there is no actual passage for air to flow through on the thermal intake gasket. However, I typically prefer to cap it off anyway.

No clamp is needed as this doesn’t see boost pressure in N/A applications. However, if you’re running a turbo or supercharger, you’ll need to secure the nipple since the boost pressure in the intake manifold could cause it to blow off.

Wow, that was a lot of information! But wait, there’s more! Let’s move on to installing the adjustable pulley.

This part was also previously on Pat’s old motor; I just removed it and reinstalled it on the new motor. I like this kit because it’s simple and easy to install. However, as I mentioned earlier in this post, the weak link of this kit seems to be the lower-quality bearing inside the pulley. I haven’t personally had an issue with this, as I’ve been using mine for years. But I know Pat has encountered the issue, as have some other people. I’ll go ahead and list the part number/box for the better bearing replacement below.

Simply unbolt the pulley and press out the old bearing, then install the new bearing. It’s a straightforward swap.

Above is the OEM power steering pump that you’ll be removing. Simply unbolt the two 12mm bolts.

Now, install the K-Tuned adjustable EP3 pulley. They include two hex bolts to secure it, which fit neatly into the bracket for a clean look. Be sure to apply Loctite to these bolts.

Above, you can see that the previous setting wasn’t going to be tight enough to work with this motor. Below, you can see the adjustable notches on the bracket.

Loosen the pulley just enough so it doesn’t move up and down too freely, but not so tight that you can’t make adjustments.

You’ll now need to release tension on the tensioner to fit the belt. Use a socket on the tensioner pulley and rotate it downward (clockwise) to relieve tension, allowing the belt to be routed around all the pulleys.

You can see how I moved it up about 4 notches.

To ensure proper adjustment, the arrow on the tensioner bracket must align within the “service window” on the tensioner itself.

Above, you can see how high the pulley is set and how it positions the arrow. This setup is out of specification and too loose.

I have now adjusted the pulley to almost the highest notch, and as you can see, it positions the arrow on the opposite side of the service window. This indicates it was too tight.

I went one notch lower, making it slightly looser, and the arrow now sits just barely within the service window. This will have to work because I don’t want it too tight, which could lead to premature wear on any of my pumps, pulleys, or bearings.

Now the motor is starting to look a lot better.

Thanks for taking the time to read the first installment of our K Swap Guide series. I know there’s a lot of information here, but I really wanted to create a comprehensive step-by-step guide that can help many people understand the process. I’m probably guilty of including too many pictures, which might slow down the page a bit, but I wanted to make sure I covered everything as clearly as possible.

I’d love to hear your feedback on this post or answer any questions you have about completing a swap. Please, as always, feel free to reach out to me via email at Billy@functiontheory.com, through Instagram DM @Functiontheory, or simply leave a comment on this post—I’ll be sure to respond to everyone.