RCM Subaru EJ# Idler Post Upgrade Conversion

RCM Timing Belt Idler Post Restoration

Precision Engineering for Maximum Timing Belt Reliability

After more than 36 years of building Subaru EJ engines, we've seen first-hand how age and repeated engine rebuilds can take their toll on the timing belt idler mounting posts.

Located on the front face of the engine case halves, these two cast aluminium posts support the large smooth timing belt idlers and play a critical role in maintaining perfect timing belt alignment. Unfortunately, it is becoming increasingly common to find worn threads, damaged mounting faces and poor previous repairs on older engine cases.

During engine disassembly, the idler posts are often subjected to impact or leverage which can bruise or distort the aluminium mounting face. Even a small amount of damage can prevent the idler from seating perfectly flat, causing it to run out of alignment. The result is incorrect timing belt tracking, premature belt wear and, in the worst cases, complete timing belt derailment leading to catastrophic engine failure.

Rather than simply repairing the damaged thread, RCM restores the entire mounting point using precision machining techniques.

Each engine case is securely mounted on our precision milling machine where the idler post is carefully indicated to ensure absolute accuracy. The mounting face is then lightly machined to restore a perfectly flat seating surface before the original thread is removed and replaced with a motorsport-grade Time-Sert® solid steel thread insert.

Because the machining is carried out on the milling machine—not by hand—the new thread is installed perfectly perpendicular to the mounting face. This guarantees the idler pulley sits perfectly square against the engine case, allowing the timing belt to track exactly as Subaru intended.

The finished result is stronger than the original aluminium thread, providing a permanent engineering solution that is ideally suited to standard road cars, fast road builds and high-performance motorsport engines alike.

Features & Benefits

• Precision restoration of damaged timing belt idler mounting posts.
• Corrects bruised, distorted or uneven idler mounting faces.
• Precision machined on a milling machine for absolute accuracy.
• Motorsport-grade Time-Sert® solid steel thread insert.
• Steel thread provides significantly greater durability than the original aluminium thread.
• Ensures the idler pulley sits perfectly square to the engine case.
• Maintains correct timing belt tracking.
• Reduces the risk of premature belt wear and catastrophic timing belt failure.
• A permanent, professional engineering solution.
• Recommended during every quality EJ engine rebuild where damage or wear is present.

At Roger Clark Motorsport, we don't believe in temporary repairs. Every machining operation is carried out with the same attention to detail that has earned RCM its worldwide reputation for building some of the finest Subaru engines available.

When precision matters, so does the engineering behind it.

Each block case has x2 posts. Pricing is per post.