Impreza Dilemma

[mrciarano]

Hi folks

My friend has been restoring a GC8 Impreza WRX that's been a bit poorly, and unfortunately it looks like a few things have gone wrong at some point in the car's life - so I'd like to share the story/info/progress so far and get your thoughts on potential problems?

Unfortunately I've not seen the car running and only got stuck in the project when the engine was taken out of the car. What I can report is that before the engine came out to do some repair work to the shell (corrosion), and it had the following symptoms:
- It would bog down full throttle after 4,000rpm
- You could take it higher than 4,000rpm if you didn't do full throttle
- The ends of the spark plugs when I pulled them were black
- When I pulled the heads off the engine absolutely stank of burnt oil and fuel - and it's definitely been running rich

Taking the EJ20 out, it's an open deck block and I suspect it's been a replacement engine out.

We went to a specialist to go buy some parts, and described the issues, who suggested we take the cylinder heads off to check for cracked valves and pistons, given the engine is cast. Since I was taking the timing belt off, I thought we may as well check. Unfortunately I'm not clued up with common issues with EJ20s/Subarus so I was willing to take the advice.

We didn't manage to do a compression test before I took the heads off as I managed to lose the adapter for the tester, so I have no idea of the condition of the piston rings. I did move each piston to TDC and check for play by wiggling the piston and they didn't seem to have any noticeable movement.

It looks like it's got a catless downpipe setup so I'm not sure it would be a catalytic converter being blocked - but I suppose it doesn't stop an exhaust packing up with muffler packing disintegrating?

I've attached some pictures of the cylinders and underside of the head - what would you do with the engine in this state? Is it worth dumping the heads into a machine shop to replace the valve stem seals? With no scoring on the cylinder walls, what's the likelihood of pistonrings causing blowby?

Would you just send it with stem seals and some O2 sensors?

TIA for your thoughts - and apologies I couldn't provide any compression test figures

Edited by mrciarano on Monday 24th February 19:16

[mrciarano]

So we decided to crack the block open and properly check the pistons and rings - naturally one of them is screwed and the skirt is showing signs of failure.

Is it worth the investment to throw forged components in an open deck block - bearing in mind really my friend is looking for longevity more than trying to make lots of power?

[TEKNOPUG]

How much power do you want to run and how much do you want to spend?

Whilst fully forged engines will allow you to run a lot more power reliably, their longevity will be less than a non-forged engine at moderate power levels.

Personally I'd buy a brand new short block engine and then fit your heads and other components to it. Will give you the ultimate in reliability and longevity if you aren't looking at big power. https://www.importcarparts.co.uk/parts-info?id=959...