K20/K24 Engine Swap Parts List for the Honda Civic (EG/EK) and Integra DC2

Start with the long block and gearbox, since every other part is matched to them. A K20 or K24 both work; the K20A2 is generally preferred over the K20A3 for performance builds. The transmission commonly comes from a Type-R, an RSX Type-S, or an RSX Base car. Note that different donors carry different gear ratios (for example an EP3 box versus a base RSX box), so decide what final drive you want before buying. If you source the engine and transmission separately rather than as a mated unit, you will also need the full set of bell-housing, starter, and alternator hardware covered in a later step.

The factory K-series does not bolt into the EG/EK/DC2 chassis without an adapter mount kit from Hasport, Hybrid, or Avid, paired with a plug-and-play harness conversion from Hasport, Hybrid, or Sparkks Racing. One easily missed piece: a K24 that did not come out of a CR-V needs the CR-V passenger-side engine mount to locate correctly. CR-V-sourced K24 engines already have the matching mount, so this only applies to non-CR-V K24 builds.

Use an RSX Type-S 02-04 engine harness and charging harness, and run either an RSX PRB 02-04 ECU flashed with Hondata K-Pro or a JDM K-series ECU. Before you sell off the old engine and its harness, cut and keep these plugs, because they are painful to source afterward: the female and male oxygen-sensor connectors from the EG/DC harness, the two-pin fan-switch connector, and the one-pin coolant-temp sending-unit connector from the D or B-series harness. Also retain the fan switch and coolant temp sensor from the outgoing motor. Note that if you wire the fans into C101 slot 7, K-Pro can control them directly and the fan switch becomes optional.

Fit an RSX Type-S clutch and flywheel and a Hybrid Racing clutch line. The clutch slave cylinder mounts to the front of the transmission with two bolts and physically moves the release fork; if your transmission already came with one you can reuse it, but if it did not, you must buy the RSX-S unit or the clutch will not disengage. Do not confuse this with the clutch master cylinder on the firewall. For an EG, use RSX Base axles with the inner joints swapped, or RSX Type-S axles fitted with B-series outers (again swapping the inner joints).

Choose an intake manifold to suit your goals: the RSX-S manifold, or an RBC, TSX, or Accord manifold. If you run the RBC manifold, add a Karcepts throttle-body adapter. Match the throttle body to the engine and intake, using an RSX Type-S or Accord unit as appropriate. On the exhaust side, budget for a custom-welded system; 3-inch stainless piping with a 3-inch in/out muffler is the reference setup, though 2.5-inch is a valid substitute. Add a catalytic converter if you intend to run one. The header can come from R-Crew, DC, or SSR.

Two routes work. To keep a stock-style radiator, use a Hasport billet hose adapter that accepts the B/D-series fan switch and coolant temp sensor, a Perma-Cool PRM-19120 11x10 fan, an RSX Type-S top hose as the upper radiator hose, and a 99-00 Civic Si top hose as the lower radiator hose (both for EK/EG). Alternatively, run an aluminum OEM-replacement radiator, or an RSX-S radiator with fabricated mounts; the same slim fan suits the OEM-replacement units. The EG factory radiator fits without relocation, but if clearance is tight a Karcepts relocation kit lets an aftermarket unit fit.

This is the cheapest reliable fuel setup and it reuses the factory fuel rail and filter. Flow runs stock filter to regulator to rail, with the regulator return going back to the car's stock return line. Parts (Summit Racing): EAR-991945ERL to convert the OEM filter to -6 AN, EAR-165056ERL to convert the OEM rail to -6 AN, four RUS-610020 straight -6 AN couplers, three SUM-220166N straight-cut -6 AN hoses for the regulator ports, a single 90-degree -6 AN coupler (RUS-610160) linking filter to regulator, one RUS-632070 10-foot length of -6 AN hose, and an AEI-13109 Aeromotive fuel pressure regulator. Add a Walbro 190/255 lph pump; it is inexpensive and worth fitting as a precaution. Priced together this setup runs around $250 before the pump.

Use Type-S fuel injectors. On a stock-head, stock-block K24/K20 swap they support roughly 250 horsepower, which is plenty for an unmodified combination. For the primary oxygen sensor, use the RSX Type-S 02-04 unit: K-Pro only reliably recognizes that specific sensor, and substituting an EP3 or 06+ Civic Si sensor has been tried and does not work. A Type-S knock sensor is needed only if you are not using an RSX-S engine, or you can repin the stock knock sensor.

To delete power steering with no A/C, add an EP3 idler pulley and bracket in place of the pump, and either fit a manual rack or convert the existing rack. To convert, loop the high-pressure port back to a return port so fluid recirculates through the rack, keeping it lubricated and debris-free; this is much easier to turn than simply removing the belt. Barbed automotive fittings and a short hose between ports do the job. You can instead just plug all the ports, which testers report feels no different. If you keep power steering (no A/C), use a K20 PS pump, a Jackson Racing pulley P/N 052-154 (clears an EG hood on a K20 swap with only cutting, no hole), the high-pressure hose off a 02-04 RSX, a length of 3/8-inch ID hose, and a Perma-Cool P/N 1007 oil cooler as a fluid return line.

With the EP3 idler in place you are not running power steering, so belt length depends on whether you keep A/C. For a K24 with no P/S or A/C, a 52-inch belt works; Dayco #5060520 is a 6-rib belt of that length that fits (no 7-rib 52-inch belt is made). A K20 in the same configuration takes a 50.5-inch belt. Deck height matters here: the EP3's K20A3 sits lower than a K24A, so a belt sized for the EP3 will come up wrong on a K24 that uses an EP3 idler alongside A/C. The reliable method is to route string through the pulleys and measure it directly for your exact setup.

Convert the shifter to cables using a Karcepts shifter mounting kit, an RSX Type-S shifter box, and RSX-S 02-04 shifter cables, then connect them with the OEM shift-linkage parts. Type-S cables are the safe choice; cheaper 06 Civic Si cables only stand a chance if you also use the 06 Si box with a comparable mounting location, so matching the box and cables to one another is what makes the linkage work.

If the engine and transmission came apart, buy the hardware set: clutch bolts 90034-P10-A01 (x6), flywheel bolts 90011-PNA-B00 (x8), transmission bolts 95701-12060-08 (x4), starter bolts 95701-12085-08 (x2), long starter bolt 90027-PND-A00, bolt 90025-PNA-000, 95701-08055-08 (x2), alternator bolts 90008-PNA-000 (x2), bolt 90008-PPA-000, and 95701-06012-08 (x3). Pilot bearing 22103-PNA-003 seats in the end of the crankshaft to center the transmission input shaft and is required. For a K24 mated to a K20A2 Type-S transmission, add cover 21351-PNB-000. Finish with fluids: 6 quarts of oil, 3 bottles of MTF, 2-3 bottles of 50/50 coolant, 2 bottles of DOT3 brake fluid, and 2 bottles of power steering fluid if retaining P/S.