Why do FA and FB engines need Rocker Retainers?Updated 19 minutes ago

The rocker arms in Subaru FA and FB engines (including the FA20 in the Toyota 86 and Subaru BRZ, and the FA24 in the GR86 and current BRZ) are floating. They're held in place only by valve spring pressure. 

What goes wrong

If a valve floats, bounces or sticks, even for a split second, the rocker is unloaded and can walk off its pivot. Because it's a boxer engine, the rockers sit on their side, so gravity makes this more likely. Once a rocker is loose:

• If you're lucky, it tucks into the head and the cylinder keeps running on its other valve. You might notice a misfire or low power.
• If you're not, the camshaft picks it up and punches it through the tappet cover. Oil sprays onto the exhaust (a fire risk), the valve can drop into the cylinder, and the engine is destroyed. A rebuild generally runs $5,000 to $10,000 once pistons, valves and gaskets are counted.

Does it only happen on track or when over-revving?

No. There's no specific RPM. A missed downshift of course makes it extremely likely, but we've seen rockers drop across the rev range on stock, daily-driven cars, including automatics. Carbon build-up on the valves makes a sticking valve, and a dropped rocker, more likely.

How our kit helps

Our kit replaces the factory pivots with our Denstoj pivots that have a retaining groove, plus a heat-treated high-carbon steel clip on each rocker. In normal running, the clip doesn't affect the operation of the rocker. However, if valve spring pressure is lost, the clip is designed to catch the rocker and hold it in place until valve spring pressure is regained. This massively reduces the risk of it dislodging.

It's not a fix for poor valve control, and a severe over-rev can still break the clips. Think of it as insurance: prestige engines like the BMW B58 in the GR Supra and Lexus 2UR-GSE V8 in the Lexus LC500 use rocker retention from the factory for the same reason.

We've been running our retainers since 2019, on everything from daily drivers to Toyota 86 Racing Series cars.