The Honda K series VTEC engine has certainly been met with mixed results from the enthusiast crowd, but from no fault of the engine or design. Many factors have contributed to the K series not being quite the smash success the B series DOHC VTEC engines of yesteryear.
We receive questions about the swap into an older Civic or Integra frequently, and to solve the litany of questions we receive on the subject, we’ve created the K20 Parts Guide. Looking for a How To Honda Swap Guide? Take a look at our What Fits What article here as well as Part 2 of our Honda Swap Guide.
K Series Engine / Transmission
There are several different options when it comes to sourcing the K series engine. One option is the K20A3 VTEC engine that’s in the seventh generation Honda Civic SI from the year ranges of 2002-2005.
There’s also the Acura RSX from year ranges of 2002-2004 with the K20A2 powerplant.
You can also opt for the larger 2.4 liter displacement K series engine found in the 2003-2006 4 cylinder Accord and other vehicles.
Part one of our K20 Swap Guide will give you the engine and transmission choices and options you have for the K20 Swap.
You can opt for any size of K series Honda motor here, from the K20 to the K24 which would bring displacement to 2.4 liters. You will need a complete engine assembly, the complete transmission assembly, and the two harnesses required to operate the engine.
In typical Honda fashion, there are many variants of the K20 that you hear about. The K20A is the original DC5 ITR engine and is as rare and popular as that sounds. The K20A2 which is what’s generally plentiful here in the US is the RSX Type S 200 hp engine. There’s also the K20Z1 that’s a 210 horsepower derivative of the K20A2, and that’s just the RSX Integras.
For those on a budget the K20A3 is an excellent engine for the price. This is the Honda Civic SI motor found in the less popular EP3 from 2002-2005. This engine puts down 160 horsepower and is a fairly priced engine that’s plentiful with the 2002-2005 Civic SI owners swapping for bigger and better.
While a tad limited in horsepower, its cheaper and a lot more fun to drive around town due to a large torque band.
In addition to the Honda Accord K24 found in the later model Honda Accords and Honda CR-V’s, the 200 horsepower version can be found in the USDM Acura TSX. The TSX engine is a great find and isn’t hard to find, or you could put together your own Frankenstein K series engine for your K swap.
This consists of the K series engine harness from a EP3 Honda Civic or the engine harness from a Acura RSX Type S or Base model. It’s best to stick to the year range of 2002-2004 for these harnesses, which will eliminate a lot of the unnecessary wiring. You will also need the charging harness from the same engine in order to connect to your vehicle and to the K series alternator.
There are several services available for the harness conversion that you will need to convert your K series harness to fit into your Civic or Integra.
Engine Accessories
If you are swapping a K20A2 from a RSX into your vehicle, you will need the starter and alternator for this engine.
The alternator for the K20A2 is part number 31100-PRB-003 and it can also be found under 31100-PRB-013. If you are swapping the K24, the alternator part number will be 31100-RAA-A01 or 31100-RAA-A03, and this alternator can also be found under 31100-RAA-A05 or 31100-RTA-023. The aftermarket interchange part number for this alternator is CSC29 or CSD73, and if you need the alternator bolts, the part number is 90008-PNA-000.
The starter for the K series engine must also be sourced if your K engine swap does not come with it.
The part number for the K20A2 or the Acura RSX is 31200-PRB-A01, while the 2.4 liter version will be part number 31200-RAA-A61. The starter will most likely have to be swapped, unless you purchased your entire donor swap as a whole. If you need replacement starter bolts, the part numbers are 95701-12085-08 x 2 for the bolts to the transmission housing. The long starter bolt is part number 90027-PND-A00.
Engine Control Unit
Engine control can be the most difficult part of our K20 Swap Guide, so make sure to choose wisely. Don’t be afraid to plan ahead for future mods when selecting the engine management of your choice.
The ECU required to run your K series engine swap can be easy depending on what your end goals are. For most people the simple choice of a PRB ECU from a Acura RSX will do the trick, if you are looking for the ultimate in performance, you can choose the Hondata K-Pro or a JDM version of the same PRB ECU.
The part number for the Kpro is HAD-K-PRO and it’s basically the end game for your computer tuning needs. Check out our Kpro install and dyno tune on a Honda GD Fit here.
Intake Options
In what could be the biggest decision for your K series swap, what throttle body / intake manifold combination? If you are intent on retaining the drive by wire feature and stock throttle body options, you can select the RSX Type S throttle body or the Accord throttle body depending on your engine or intake manifold.
You can either choose to run the RSX Type S throttle body (shown above) with the matching intake manifold, or switch to a TSX or Accord setup from a K24. You can of course always choose aftermarket routes, which would require a RBC and throttle body adapter at the very least.
Mount Kit
There are many mount kit choices available, from Hasport to other copycat companies, many kits give you a complete turnkey solution. Most of these kits are made for the 1992-2000 Honda Civic or 1994-2001 Acura Integra, but other choices do exist.
Other mounts you may require if you are not going the normal Hasport mount kit route, but you may need a Honda CR-V K24A1 passenger side engine mount. The Honda CRV passenger side mount is part number 50840-S7C-980 and is required if you are putting your mount kit together separately.
Exhaust
Because the K series exhaust faces towards the vehicle firewall, you have a few options here when it comes to aftermarket support. Many popular aftermarket choices are solid for header selection, from DC Sports to SSR or R-crew.
Once you have the header and catalytic converter choice sorted out, you can merely choose the catback of your choice that will fit your chassis.
Sensors required in our K20 Swap Guide
The Knock Sensor is an important part of your K series engine swap starting, and for good reason. Without the signal the knock sensor provides, your ECU will not know when predetonation or engine knock occurs in your engine.
This sensor is basically a microphone that allows the ECU to realize when the engine is encountering dangerous operation. This sensor will notify the ECU which will then pull ignition timing to attempt to stave off engine knock, or go into limp mode.
The part number for the K20A2 Knock sensor is 30530-PRB-A01, and is connected to the K series shortblock.
RSX Oxygen Sensor ( PRIMARY )
You’ll need just the upstream 02 sensor, unless you are intent on CARB legalizing your K series engine swap. The primary oxygen sensor on the K20A2 is found in the header B pipe, towards the rear of the engine.
The primary 02 sensor for the K20A2 is part number 36532-PRB-A01, you can also opt for a universal style four wire 02 sensor and simply wire it to the oxygen sensor connector.
Drivetrain K Swap Components
Because you are installing the K series engine into a different vehicle, you will need new axles and the proper halfshaft if you want to use OE Honda parts. For a 1992-1995 Honda Civic swap, you’ll be using the RSX Type-S halfshaft with a combination of outer or inner axle components from your target vehicle.
For example to swap a K series into a 1992-1995 Honda Civic EG, you will need the Type S halfshaft, with the RSX base model axles. The base model axles will need you to swap the inner joints and U joint with the EG versions to fit. For 1994-2001 Acura Integras, you can use the Type-S Axles with GSR outer axle components.
The best possible option however is to purchase a driveshaft shop axle kit or a premade axle kit made to the lengths you need. If you have any questions about fitment, please let us know in the comments below.
You should also locate and purchase a new set of clutch bolts and flywheel bolts with the appropriate anti-seize. The K series flywheel bolts are part number 90011-PNA-B00, you will need eight of these. The clutch bolts that button the clutch plate and disc to the K series flywheel are part number 90034-P10-A01, of which you need six.
If you are using an aftermarket clutch or a specialized dual or triple plate clutch, the throwout bearing that is to be used should be supplied. Always service your pilot bearing as well, the part number is 22103-PNA-003 for the K series pilot bearing.
Shifter Components
Because you will be leaving the world of rod actuated transmissions behind, you will need a shifter mounting kit to mount the new K series shifter box and cables. There’s quite a few options for the shifter mounting kit, we prefer the units from Karcepts which feature everything you need for install.
You will also need a RSX Type S shifter box and shifter cables required to mount and install your shifter cables. Because this shifter box assembly requires some serious modification, make sure you can shift into all gears before finalizing the mounting process.
Clutch Slave Cylinder
The Acura RSX Type S Clutch slave cylinder is what’s needed here if you are converting to a six speed transmission. Because you are using the K series transmission, part of the K20 Swap Guide is converting the slave cylinder as well. The part number for the cylinder is 46930-S7C-E01, and you will also need a clutch line to go from your master to the new K series slave cylinder.
Power Steering
To retain power steering in your new K series swap, you will need a K20A power steering pump and the high pressure hose from a 2002-2004 Acura RSX. It’s also a good idea to run a power steering cooler to help keep your power steering fluid from breaking down.
To complete the install of power steering in your K swap, you will need a pulley kit like the one from Jackson Racing part number 052-154. This pulley mount will help the power steering pulley and belt clear most hoods and engine bays.
If you are not retaining power steering, you will need the Honda Civic SI EP3 idler pulley and bracket. On the K20 the serpentine drive belt will be 50.5 inches long and the K24 will use a 52″ serpentine drive belt.