hmhaga

Sorry for yet another topic on the matter. Have a 03 C5Z with 93.000 miles, where I need to address some issues (mainly oil leaks) before putting it back on the road for the summer and track days. First year of ownership, had the car to 3 track days, with no major issues (except the oil leaks and high oil temperature). When you browse the net for specific issues, you find what you search for - heaps of problems. I've owned Subaru's for 20 years with no breakdown, search the net and the boxer engines are disasters waiting to happen with blown head gaskets and oil burning issues. I guess the owners with no problems are out driving, not posting on the net

C5Z has yellow valve springs. Easy to address, so I will replace. But with 93.000 miles, will they actually fail now?
This also makes it easy to address the trunnions, but again - is it only internet hype? How many of you have ACTUALLY experienced this on a 03 or newer car? NO needles in the oil pan and no sign of problems. I'm also reluctant to replace heavily engineered parts with 3rd party parts of unknown quality, which can introduce new issues (bushings - increased mechanical resistance, load distribution, lubrication issues, material quality etc).

SaberD

I had a Subaru that spun a rod bearing within a month of owning it. They really are as problematic as you read online. I would definitely change out the yellow springs. I'd install the Straub bushing kit also. The needle bearing failures do happen even on stock motors. It's best not to risk it.

93Polo

I would replace the valve springs, especially as you said track days. The original owner of my '01 Z (which had a smaller cam than the 02-04 C5Zs) broke a spring doing track days. IMO they are a wear item once you start doing HPDEs, and OEM replacements are not that expensive.

Trunnions, your call. Inspect the tips on the rockers and pushrods when replacing the springs, if you see more wear on either tip obviously replace the worn part. If you do replace the trunnions I'd go with a new GM rocker assembly or a bushing upgrade such as Straub, CHE, Smith Bros etc. If they start to get worn the bushed versions will likely make noise rather than just spitting needle bearing parts into the motor.

If you replace the clutch, inspect the couplers and bearings in the torque tube and add a remote bleeder.

A good catch catch can is nice to keep the motor from internally consuming oil. I like the Mighty Mouse catch can and as you're running track events replace the K&N style breather top with the sealed cap running a hose to the intake tract. If the catch can does get over filled, it is better to consume the oil, rather than puking it in the engine bay and under the car.


SAC City has some good tools to align and install seals. Harmonic balancers are a known problem, if you replace the front main seal, do a Powerbond or preferably ATI balancer with an ARP bolt,

Overall the C5 is a tough, relatively low maintenance platform to do track days. Yes like Subies problems are known which doesn't mean you're destined to experience them and regular maintenance and a few mods will go a long way. The Autocross section has plenty of info on prepping the car for HPDEs. I do recommend an engine oil cooler to keep those temps down, and replacing the radiator with something like a DeWitts for increased cooling and aluminum ends tanks rather than plastic. Depending on how you use the car and where you are located many recommend an oil cooler adapter with a thermostat.

hmhaga

Thanks! I have an engine oil cooler waiting for install, as time and speed on the track is now governed by the oil temperature, Will do a more thorough inspection of the rockers etc when changing the springs.

turabo87

I just got to 94k miles myself. Up until 90k the engine was stock without signs of being tampered with. At 90k I decided to address some worn items and possible ticking time bombs such as valve springs, trunnions, crank damper/harmonic balancer (this one was really shot and starting to come apart; the rubber ring was squeezing out of place). Honestly, for me it was the crank harmonic balancer that pushed me to do a lot of things at once. Did other items as well since I'm already in there such as my oil pump and front cover oil seal and took the "maintenance opportunity" to make more power and sweet music by going to a medium cam. I also incorporated other performance bolt ons such as long tube headers, LS6 intake....etc. Typical snowball effect of deep maintenance that becomes a good size build and an excuse to make more power along with more reliability/longevity.