Choosing the right parts:
Subaru WRX
Turbo/Camshaft Upgrade



Let’s move onto the camshaft replacement. Like with most engines, the timing marks should be aligned prior to removing the timing belt. Unlike most engines which align at TDC, the EJ20 timing marks place the pistons midway between TDC and BDC to avoid contact between the valves and pistons. With the crank in this position, the only way you can bend a valve is by moving both cams and colliding the valves into each other. The trick is to only move one cam at a time.



The most difficult part about this job is removing the cam gears. While the task sounds easy, the bolts are really tight and require a huge amount of torque to break loose. AMS Performance sells these tools to hold the cam gears and they worked great on the intake side…


But due to the brittle composite material on the exhaust gear, most of the teeth stripped out on us.


The best method we figured out is to lock the gear down with an old belt and multiple vice grips. While this sounds super sketchy it works every time when done properly. Search the web if you need more details on how to do this.


With the cam gears off, replace the old camshafts with the new ones.


This is where the job gets a bit tedious. The valves have to be adjusted and to do so start by measuring the valve lash with a feeler gauge.



While some of the early EJ20s had a shim over bucket lifter design, this proved to be unreliable so Subaru switched to an integrated shim and bucket design. In other words, you need to replace the entire buckets (available at Subaru dealers) to adjust the valves. Unfortunately, this means removing the cams multiple times until you get the lash within specs. Be sure to write down the shim/bucket size to avoid doing this job over and over and over…and over.



Since the engine is going to be apart and you’ve already seen how much work that involves, it’s a very wise move to replace all the maintenance parts on it like water pump, pulleys, and gaskets. We sourced everything from RPM Auto Parts in Costa Mesa.


Because our stock exhaust gears were brittle and cracked we replaced them with these totally bling-worthy Tomei adjustable Cam Gears. Having adjustability on the gears can help degree aggressive cams and also add or retard timing for better maximum performance. Although, that practice should be left to the professional tuning your engine.


We also purchased a Tomei Strengthened Timing Belt for peace of mind since we didn’t know when the last one was replaced.



With the new belt in place, the timings marks should align like they did when you took them off.


The camshaft swap is complete so you can reassemble the rest of the engine components and move onto the turbo upgrade.

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Subaru WRX
Turbo/Camshaft Upgrade"

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Everything you always wanted to know about building a EJ but were too afraid to ask. Awesome job documenting this.