F20C vs F22C1: Internal Differences and Valve Retainer Upgrades for AP1 Owners
There’s a particular moment that every AP1 owner knows well—the tachometer needle sweeps past 8,000 rpm, the VTEC crossover hits, and the engine lets out a howl that makes you forget you’re driving a car built in the late 1990s. But that glorious high-rpm party comes with a catch.
If you own an early Honda S2000 with the F20C engine, you’ve probably heard the warnings about valve retainers cracking, especially after an over-rev. And if you’ve ever wondered what makes the F22C1 from the AP2 different—and whether those AP2 parts can save your engine—this guide is for you.
TL;DR
The F20C (2.0L) and F22C1 (2.2L) are both legendary VTEC engines, but they differ significantly in stroke, redline, torque delivery, and valvetrain components. Early AP1 F20C engines have known valve retainer weaknesses that can lead to catastrophic engine failure. Upgrading to AP2 retainers is a common, highly recommended preventative fix. The F22C1’s retainers are stronger, and using them in the F20C—along with the matching keepers—is the preferred solution for reliability.
Key Takeaways
- The F20C revs to 9,000 rpm and produces up to 250 PS, but its intake valve retainers can crack over time.
- The F22C1 has a longer stroke and more low-end torque, but it revs lower and has a slightly different character.
- AP1 owners should proactively replace their intake valve retainers with AP2 or upgraded aftermarket units to avoid a dropped valve.
- The upgrade uses genuine Honda parts: 14765-PRB-A01 retainers and 14781-PCX-004 keepers .
- A valve adjustment and inspection of your current retainers is highly recommended during this service.
The Tale of Two Engines: F20C vs F22C1
The Honda S2000 originally arrived with the F20C, a 2.0-liter, naturally aspirated inline-four. It was a masterpiece of engineering, and it made some serious waves when it launched.
But in 2004, Honda introduced a 2.2-liter version for the North American market called the F22C1, which would later become the global engine for the S2000. Here’s what changed.
Displacement and Dimensions
| Specification | F20C | F22C1 |
|---|---|---|
| Displacement | 2.0L (1,997 cc) | 2.2L (2,157 cc) |
| Bore | 87mm | 87mm |
| Stroke | 84mm | 90.7mm |
| Rod Length | 153mm | 149.65mm |
| Rod/Stroke Ratio | ~1.82:1 | ~1.65:1 |
The F22C1 uses a longer stroke to increase displacement by 160 cc, which gives it more low-end grunt at the cost of a slightly shorter rod ratio.
Power and Torque
The F20C makes its power at the very top of the tachometer.
- JDM F20C: 250 PS at 8,300 rpm, 218 Nm at 7,500 rpm
- USDM F20C: 240 hp at 8,300 rpm, 153 lb-ft at 7,500 rpm
- F22C1 (USDM): 240 hp at 7,800 rpm, 162 lb-ft at 6,500 rpm
What does this mean in practice? The F22C1 gives you more torque much lower in the rev range. You feel it around town and on the street, where the AP2 feels stronger and more flexible. Meanwhile, the F20C is a top-end monster—you have to wring its neck to get the full experience. Some owners argue the F22C1 sacrifices the F20C’s manic, race-car character in exchange for daily drivability .
Redline and Rev Limit
- F20C: Redline at 8,800 rpm, fuel cut at 9,000–9,150 rpm
- F22C1: Redline at 8,000 rpm, fuel cut at 8,200 rpm
That 900+ rpm difference changes the entire personality of the car. The F20C feels like it’s always building, always climbing, always ready to scream. The F22C1 feels more relaxed, trading that manic energy for usable torque.
Compression Ratio
The F20C has a higher compression ratio (11.7:1 in JDM spec, 11.0:1 in USDM) compared to the F22C1’s 11.1:1 . This contributes to its high specific output.
The AP1 Valve Retainer Problem: Why You Should Care
Here’s the thing about the F20C: the engineers pushed the limits of what was possible with lightweight valvetrain components. The intake valve retainers in the AP1 were designed to be incredibly light to help the engine rev so freely, but the tradeoff is durability.
These retainers can develop hairline cracks over time, and one over-rev event—a missed shift from 6th to 3rd, a money shift, or just spending too much time near the limiter—can cause them to fail . When a retainer cracks, the valve can drop into the cylinder. This usually means the piston slams into the valve, bending or destroying both, and often requiring a full engine rebuild or replacement.
“AP1 owners: please replace your valve retainers and keepers (aka cotters) with AP2 or aftermarket retainers and keepers!… When the engine is running over 9000RPM, the valves float and a result the valve springs close at full force.”
Forums are full of owners who discovered cracked retainers during routine valve adjustments, even on cars that weren’t driven hard . The cracks are visible as a sunken or deformed appearance on the top of the retainer. The good news? This is fixable.
The Solution: AP2 Valve Retainer Upgrade
Honda addressed the issue by using stronger, more robust retainers in the F22C1 engine . The best part? These upgraded parts bolt right into the F20C head.
This is a direct-fit, preventative maintenance upgrade that AP1 owners should seriously consider.
The Genuine Honda Valve Retainer Upgrade Kit typically contains :
- 8x Upgraded Retainers: Part number 14765-PRB-A01 (these go on the intake side, which are the ones that fail)
- 16x Matching Keepers (Cotters): Part number 14781-PCX-004
Important: You don’t need to remove the cylinder head to do this job. It can be done with the head on the car by simply removing the valve cover . However, it does require some specialized tools (like a valve spring compressor), and you’ll definitely want to do a valve adjustment while you’re in there.
Experts on the forums strongly recommend staying with genuine OEM parts for this.
“The factory parts for this car are virtually always the best ones available anywhere, for any price. Otherwise, just do the AP2 retainers and cotters and leave the rest of it alone.”
Chart: F20C vs F22C1 Power Delivery Comparison
F20C vs F22C1 Character Comparison
FAQ Section
Q: What is the difference between F20C and F22C1 engines?
The F20C is a 2.0L engine with an 84mm stroke and a 9,000 rpm redline, while the F22C1 is a 2.2L engine with a longer 90.7mm stroke and an 8,200 rpm redline. The F22C1 has more low-end torque.
Q: Why do AP1 F20C valve retainers crack?
They were designed to be lightweight to help the engine rev, but they can develop hairline cracks from stress, especially after an over-rev event like a missed shift .
Q: What are the symptoms of a cracked valve retainer?
You might not feel any symptoms until failure. Visible signs during a valve adjustment include a sunken or deformed appearance on the top of the retainer .
Q: Can I use AP2 retainers in my AP1 F20C engine?
Yes, this is a common and highly recommended upgrade. The AP2 retainers are stronger and bolt directly into the F20C head .
Q: Do I need to remove the engine head to replace the retainers?
No, the retainers can be replaced with the cylinder head still on the car by removing the valve cover .
Q: What parts do I need for the AP1 retainer upgrade?
You need 8x upgraded retainers (Honda 14765-PRB-A01) and 16x matching keepers (Honda 14781-PCX-004) .
Q: Should I use aftermarket retainers instead of Honda parts?
Most experienced owners recommend genuine Honda parts for this job, as they are known to be the best balance of strength and reliability .
Q: Is the S2000 F22C1 engine stronger than the F20C?
It has a stronger valvetrain and more low-end torque, but its lower redline means it doesn’t produce the same high-rpm thrill as the F20C.
References
For further reading on Honda F-series engines and S2000 maintenance:
- Honda F20C engine – Wikipedia
- S2KI Forums – AP1 Retainer Replacement
- Jalopnik – Why the F22C1 Was Unique to the US
The F20C and F22C1 are both incredible engines, each with its own personality. If you’re an AP1 owner, taking the time to inspect and upgrade your valve retainers isn’t just good maintenance—it’s protecting one of the most special engines ever built.
Have you replaced your AP1 retainers yet? What did you find when you popped the valve cover? Drop your thoughts in the comments below.
