The short version
Why FA and FB rockers fall out
- The flaw: the rocker arms in the FA20, FA24 and FB engines are only held in place by valve spring pressure. If a valve sticks, floats or bounces for a split second, the rocker is free to walk off its pivot.
- The damage: a loose rocker can be flung through the rocker cover by the camshaft, spraying oil onto the exhaust. Worst case, the valve drops and takes out the piston.
- Who it affects: every Toyota 86, GR86, BRZ, FR-S and FA/FB Subaru. Stock or modified, manual or auto. The spring recall and the GR86's new springs don't change it.
- The fix: retain the rocker, like BMW and Lexus do on their performance engines. Our grooved pivots and clips catch the rocker until the spring takes control again. They're a drop-in replacement and do nothing at all in normal running.
Everything in this article is in the 11-minute video above. Short on time? Every section has a Watch this part link that jumps straight to the relevant moment.
What happens when a rocker lets go
When a valve spring loses control of its valve, the rocker arm sitting on top of it can fall out of place. What happens next depends on luck:
- The lucky outcome: the rocker drops into the head and stays there. The engine misfires and loses power, but nothing else breaks.
- The common outcome: the camshaft picks the rocker up and fires it through the rocker (tappet) cover. Oil sprays onto the exhaust headers, which can start a fire.
- The expensive outcome: with no rocker controlling it, the valve drops into the cylinder and the piston hits it. That's a head, a piston, and often a block. Rebuilds typically run $5,000 to $10,000.
Warranty claims are often put down to over-revving. Sometimes that's true, but rockers also let go at normal revs and on daily drivers.
Watch this part 0:00"Apparently my rocker decided to exit stage right. Car is a 2016 with 35k miles. Head is trashed, along with the block and a cam."
Toyota 86 owner, from the video
How the FA valvetrain works
The valvetrain controls when the valves open and close: how the engine breathes. The camshaft's lobes push the valves open, and the valve springs pull them shut again.
On older Subaru EJ engines, the camshaft sits directly above the valves and pushes on them itself. On the FA and FB engines, the camshaft sits off centre, so a rocker arm transfers the motion. One end of the rocker sits on a solid pivot, the other end sits on the tip of the valve, and the cam presses on a roller between them, closer to the valve end.
It's a good design. Rockers give more valve lift from a smaller, lighter cam lobe, which means better efficiency, less wear and a more compact engine. But there's a catch: nothing holds the rocker in place except valve spring pressure. It's a "floating" rocker.
Why spring pressure isn't enough
In theory, the right spring pressure keeps the valve under control at all times. In the real world, over the life of an engine, there are edge cases no spring can cover:
- Valve float: at high RPM, the spring can't close the valve as fast as the cam wants it to. A missed downshift that spins the engine well past redline is the classic trigger.
- Valve bounce: instead of seating cleanly, the valve bounces off its seat.
- Valve stick: carbon build-up makes the valve stick open for a moment, at any RPM.
Any one of these unloads the rocker for a fraction of a second, and that's all it takes.
The FA's boxer layout makes it worse. The rockers sit sideways, so gravity pulls them off the pivot instead of helping to hold them on.
Watch this part 3:50Engines that already clip their rockers
If a rocker only needs holding for the split second the spring isn't in control, why not hold it? That's exactly what more expensive engines do from the factory:
- BMW B58 (Toyota GR Supra): each rocker has a small spring clip that stops it falling off if there's valve float at high RPM.
- Lexus 2UR-GSE (LC 500): clips on the rockers too.
So why doesn't the FA have them? Cost. The 86 and BRZ are entry-level sports cars, built to a price. Clips mean extra parts and extra manufacturing steps, and those are the first things cut on a budget car, while a flagship gets every bell and whistle.
Watch this part 4:35Why the usual fixes don't work
These are the fixes we get asked about most. Each one helps with something, but none of them stops the rocker from floating.
| Fix | What it actually does | Holds the rocker? |
|---|---|---|
| The 2012 valve spring recall | Replaced springs that could fracture. Fractures still happen with the replacement springs, and the rockers are still floating. | No |
| Correct valve clearance | Good maintenance, and worth doing. But if a valve sticks or bounces, a correctly adjusted rocker can still fall out. | No |
| Stiffer valve springs | Reduces the chance of valve float. It doesn't stop bounce or stick, and too much spring rate wears the valvetrain faster. | No |
| 2022+ GR86 / BRZ beehive springs | A different spring design. The FA24's rockers are still fundamentally floating. | No |
| Our Rocker Retainers | Physically catch the rocker until the spring takes control again. | Yes |
The fix: retain the rocker
We built our first set in 2019, after blowing up three engines racing in the Australian 86 series. The idea is simple: do what BMW and Lexus do.
- A redesigned pivot with a groove machined into it, made from heat-treated billet alloy steel.
- Our Rocker Retainer clip made from heat-treated high carbon steel. It hooks into the groove.
In normal running, the groove is wide enough that the clip never touches the pivot. It only comes into play when a valve loses control and the rocker tries to lift. The clip catches it and holds it in place until the spring takes over again.
- Drop-in: replaces the OEM pivots. No machining of the head or rockers.
- No downsides in normal running: no noise, no wear, and minimal added weight when fitted correctly.
- Race proven: we've run them in race motors and inspected them at teardown.
- Complete: one kit does both heads: 16 pivots and 16 clips.
Why not just cut a groove in the factory pivots? The OEM pivots are only surface hardened. Machining a groove exposes the soft steel underneath, which is why we make our own fully hardened pivots.
Watch this part 6:52Will it happen to my car?
Straight answer: probably not, but you can't know in advance. Like an oiling issue, it won't happen to every engine. It's a risk to be aware of, and one that goes up the harder you use the car.
Your risk is higher if you:
- Track the car, or drive it hard on the street
- Have added power, especially a turbo or supercharger
- Have ever missed a downshift
- Have a high-kilometre engine with carbon build-up
- Have rebuilt the engine, or are about to. After a rebuild you've got more money in the engine to lose.
The maths is simple: an $879 kit versus a $5,000 to $10,000 rebuild, plus the weeks off the road.
Watch this part 8:31Proof
"I've done pretty much everything you can do to this motor, and there's no better way for me to protect that investment than with a set of Denstoj rocker arm retainers."
Joe, 500 hp turbo Scion FR-S
"I was one of the victims with a rebuilt motor. The camshaft shot the rocker through the cover and oil came out everywhere. Since then I've had the retainer kit in the car for three years. No rocker arms falling off, no oil leaking."
Toyota 86 owner, from the video
Read all reviews or watch owners fitting the kit themselves.
Watch this part 8:42Who we are
Denstoj Auto Centre is a family workshop in Newcastle, Australia. Daniel and Mitchell are mechanical engineers (Toyota, GM Holden, Tesla, and GM in Detroit), and our dad Dennis has been a mechanic for over 40 years. We rebuild RB26, SR20, 4G63 and FA20 engines, and we built this fix because we were sick of paying for blown motors.
Fitting and fitment
Does it fit my car?
The kit fits all Subaru FA and FB engines (FA20D, FA20F, FA24F, FB16, FB20, FB25), including:
- Toyota 86 (2012 to 2021) and GR86 (2022 on)
- Subaru BRZ (2013 on) and Scion FR-S (2013 to 2016)
- Subaru WRX (VA 2015 to 2021, VB 2022 on)
- Subaru Impreza, Forester, Crosstrek, Legacy, Outback and Ascent with FA/FB engines
It suits naturally aspirated and boosted engines, manual and auto, and both left- and right-hand drive. Not sure? Check the full applicability table.
How hard is it to fit?
- We recommend engine out. It's easiest with the gearbox still attached.
- About an hour per side once the engine is out.
- Standard valve lash procedure. No special measurements.
- A careful home mechanic can do it. If you'd rather not, we offer drive-in, drive-out fitting in Newcastle.
The best time to fit it is when the engine is already apart: a rebuild, cams, a head gasket or a clutch job. Read the fitting instructions.
FAQ
Does this happen on stock cars?
Yes. The rocker is floating on every FA and FB engine, stock or not. Valve stick from carbon build-up can happen at any RPM, including on a daily driver.
Didn't the valve spring recall fix it?
No. The 2012 recall replaced springs that could fracture. It didn't add any way of holding the rocker in place, and fractures still happen with the replacement springs.
Is the 2022+ GR86 and BRZ affected?
Yes. The FA24 got redesigned beehive springs, but the rockers are still fundamentally floating.
Won't stiffer springs or correct valve clearance stop it?
No. Both help, but neither holds the rocker. Stiffer springs reduce valve float but not bounce or stick, and they add valvetrain wear. Correct clearance is good maintenance, but a sticking or bouncing valve still unloads the rocker.
Are there any downsides? Noise, wear, weight?
No. The clip only does anything when the rocker becomes unloaded. Fitted correctly, it's silent, causes no wear, and adds minimal weight to the valvetrain.
Can I buy just the clips, or groove my own pivots?
No. The factory pivots are only surface hardened, so machining a groove exposes soft steel. Our pivots are fully hardened with the correct groove profile, and the clips only work with them.
Do I need to pull the engine?
We recommend it. You can reach the rockers with the engine in the car, but engine out is faster, cleaner and far less likely to go wrong. Allow about an hour per side once it's out.
Does it work on turbo engines?
Yes, and they need it more. It's running in turbo builds making 500 to 750+ hp, and fits the WRX's FA20DIT and FA24DIT.
More questions? See the full FAQ or email support@denstoj.com.au. We reply to everyone.
Push the limit. Not past it.
Retain your rockers
16 hardened pivots and 16 clips for both heads. A$879, shipped worldwide from Newcastle, Australia. You can request a return within 30 days of receiving it (see our refund policy).
0 comments