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2.4 16v - K24
Manufacturers
2.4 16v - K24
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Set of 8 reinforced exhaust valves for the Honda K24Z.
The K24Z engines are the 2,354 cc four-cylinder units (87 mm bore, 99 mm stroke) of Honda's K series, with twin camshafts and 16 valves. From 2007 they power the Accord VIII and IX, the Civic IX 2.4, the CR-V III and IV 2.4 and the Odyssey 2.4.
Their cylinder head carries 8 exhaust valves. In standard size, the valve offered has a 31 mm head, a 5.45 mm stem and a 109.3 mm overall length, longer than the K20A exhaust valve.
Each opening of the exhaust valve sends the hottest gas of the cycle across its head: the metal reaches 760 to 870 °C on a naturally aspirated engine and more than 1,000 °C with forced induction. The seat removes about 75 % of it and the guide about 20 %. An EV8 family steel gives the order of magnitude: 550 MPa at 600 °C, 300 MPa at 800 °C. Overloaded, the head fatigues, distorts and loses its seal.
The valve offered is made of Super Alloy, a nickel-based alloy, and belongs to the Competition Plus range, which brings 20 % more hot strength and 25 % longer seat life.
The F2391P takes the head to 32 mm: the burnt gases leave faster and scavenging improves, with about 10 to 12 cfm of extra flow per millimetre of head, provided the exhaust seats are machined to that diameter.
| Part number | Brand | Size | Head Ø | Stem Ø | Length | Grooves | Material |
|---|---|---|---|---|---|---|---|
| F2389P*8 | FERREA | Standard | 31 mm | 5.5 mm | 109.3 mm | 1 | Super Alloy (nickel-based) |
| F2391P*8 | FERREA | +1 mm | 32 mm | 5.5 mm | 109.3 mm | 1 | Super Alloy (nickel-based) |
| Part | Honda original | Reinforced |
|---|---|---|
| Collets | 14781-RGM-A01 | K10034 (single groove) |
| Valve stem seals | 12210-PZ1-003 / 12211-PZ1-003 | VS1002*8 / VS-H5.5E-8 |
| Valve guide | 12205-PNA-305 (repair size) | GDE-HK55-E-8 |
Check the valve lock groove against the collets you reuse before refitting the springs.
At 31 mm the seats keep their diameter; with the 32 mm F2391P, the 8 exhaust seats are cut to size.
Both part numbers share the same 5.5 mm stem and 109.3 mm overall length: the original guides are fine if they are within tolerance.
 | FERREA, founded in 1978, makes its valves in Florida and Argentina. For the K24Z it offers a Super Alloy exhaust valve, in standard size and +1 mm. |
Only the size separates the two versions:
| Criterion | Option 1 | Option 2 |
|---|---|---|
| Size | Standard, 31 mm Original seats kept. F2389P. | +1 mm, 32 mm More flow, seats machined. F2391P. |
| Model | Engine code | Power | Years |
|---|---|---|---|
| Accord VIII 2.4 (CP2) | K24W7 / K24Z2 / K24Z3 / K24Z7 | 180-204 hp | 2007- |
| Accord VIII 2.4 i (CU2) | K24W7 / K24Z2 / K24Z3 / K24Z7 | 201 hp | 2008-2015 |
| Accord VIII Tourer 2.4 i (CW2) | K24W7 / K24Z2 / K24Z3 / K24Z7 | 201 hp | 2008-2015 |
| Accord VIII 2.4 (CS) | K24W7 / K24Z2 / K24Z3 / K24Z7 | 193 hp | 2007-2012 |
| Accord IX 2.4 (CR) | K24W7 / K24Z2 / K24Z3 / K24Z7 | 185-188 hp | 2012- |
| Civic IX 2.4 (FB6) | K24W7 / K24Z2 / K24Z3 / K24Z7 | 204 hp | 2011-2016 |
| CR-V III 2.4 4WD (RE) | K24W7 / K24Z2 / K24Z3 / K24Z7 | 188 hp | 2011-2012 |
| CR-V IV 2.4 (RM1, RM3) | K24W7 / K24Z2 / K24Z3 / K24Z7 | 188 hp | 2012-2016 |
| Odyssey 2.4 (RB3) | K24W7 / K24Z2 / K24Z3 / K24Z7 | 180 hp | 2009-2013 |
| Odyssey 2.4 i-VTEC (RC1) | K24W7 / K24Z2 / K24Z3 / K24Z7 | 175 hp | 2013- |
OEM part number (exhaust valve): 14721-R40-A00; 14721-R44-A00
With a K24Z cylinder head off, it is the right time to replace the inlet valves and the valve stem seals as well.
| K24Z3 K24Z7 inlet valves → |
