Looks like the head gasket on my MY99 WRX is leaking. The clutch is also knocking on heaven's door. I've decided to get both the head gasket and clutch replaced at the same time. Whilst the motor is out I'll be rectifying a few other issues (cv/rack boots, shifter knuckle).

By way of background I bought the car as a toy/project. The whole point of the exercise was to own a tidy near-stock classic that I could modify over time to suit my taste and take for the occasional squirt at a track. There's 160,XXX on the chassis and motor. Apart from the mechanical issues it's in pretty good nick. It is not a daily driver.

That being said, while the motor is out are there any cheap/worthwhile mods/upgrades I should do to improve the longevity of the motor and, in a sense, future proof for very occasional track work? I'm hoping to take advantage of the labour cost involved in the HG/clutch jobs.

Can anyone recommend a clutch? Would the Exedy OEM replacement suffice?

Unless you know for sure they've been changed I'd do the water pump and timing belt while GPU at it.
Oh, and cam seals.

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Thanks for the reply. Cam seals have been factored in. From memory timing belt and water pump were replaced at about 142,XXXkm.

I had my head gaskets go in my '99 STI, while the motor was out I did the following;

- Had heads serviced by reputable workshop (The Engine Shop, Canning Vale)
- Cleaned up block faces
- Replaced head studs with nitrated Subaru items
- Replaced Cam Seals
- Replaced coolant hardline that runs up and over the block from the thermostat area due to corrosion
- Replaced every single coolant hose and hoseclamp. Used genuine Subaru hoses and worm-drive hoseclamps. Do not reuse the springy original clamps, I had one leak despite cleaning the hardlines and using aviation paste and had to pull the manifold off again to fix it...
- Replaced intake and exhaust manifold gaskets & turbo gasket
- Replaced any old looking vacuum lines (be aware of the restrictor pill in the lines near the turbo wastegate, probably best to leave those alone)
- Fitted aftermarket alloy radiator
- Fitted Group N engine mounts
- Replaced brake booster due to signs it had been leaking
- Painted around the battery tray where a battery had once leaked
- Cleaned up wiring - replaced conduit & retaped
- Painted engine crossmember & steering rack
- Cleaned and cleaned and cleaned and cleaned everything I could get my hands on

A couple of things you could do that will be made a lot easier by having the motor apart are;

- Fit a silicone under-manifold intake pipe (~$250)
- Fit a 3 port oil catch can/Air Oil Separator (can use the hard line that runs under the manifold, a lot easier to set this up with the manifold off the car) (~$350)
- Fit Group N Engine Mounts (~$100 from Maximum Motorsport)
- Fit an oil pressure gauge sensor onto the block
- Change out spark plugs & leads
- Change rocker cover gaskets (use genuine Subaru gaskets)
- Fit ARP head studs (If you're still running the standard motor, ARP 2000's will be fine) (~$300)
- Fit a sump baffle plate & aftermarket oil pick-up (Killer B offer these parts, make sure you get them for the correct shaped sump!) (~$350)

Exedy OEM replacement will be fine if you're running the 5 speed.