EJ20 Bore Scoring

I have ej20 engine with forged cosworth pistons built as 2.1 stroker. It has around 60k km on it. It was consuming a lot of oil most likely caused by one of the heads. Once I removed heads, I noticed mild bore scoring on all cylinders. Most of them are visible but not felt under fingernail. Some are felt by fingernail but not the way to stop it.

I need an advice, should I go with reboring to next oversize and replacing pistons or its something the engine can live with? Or maybe honing with rings replacement will be enough? Let me know what you think from your experience. Photos attached.

The engine can live with it, but you will it will have high oil consumption, and probably be down on power. You can check with the machine shop and try honing first, but the end result may be excessive piston clearance and which will require re-bore and new pistons. I suggest doing it right -- it's always worth it if you are enjoying the car and planning on keeping it.

For that sort of bore scoring it suggests there's been quite a lot of debris, or dirt, getting into the engine - usually because it wasn't cleaned thoroughly during assembly, or run without an air filter. Oh, have you had a turbo' failure that may have sent crap through the engine? Another potential cause may be crap left in the charge cooler during manufacture - it's down to you to make sure everything is clean, as those making the parts for your car don't have cleanliness as a priority. You should chase up the reason before re-assembling it, to prevent it happening again.

As David said, the engine should run OKish, especially with a light hone to remove any proud edges to the scores, but it'll never have the seal a smooth bore wall will provide. The worst scenario is if there's sufficient leakage of high pressure and temperature combustion gases to start eroding the piston skirts and possibly causing failure from scouring - but that rather unlikely.

If you have the budget, and want to keep the car, a rebore for a virgin surface will be best and give the longest service life - if you find out how the debris got into the engine initially and remedy it.

While you're at it, carefully inspect the valve seats, materials are much better nowadays, but there is a possibility of the seating face(s) also being marked.

Thanks a lot guys for elaborate reply. Honestly, not sure if any debris got into the engine, at least not on my watch. I am a 3rd owner since the rebuild so there is a chance that one of previous owners did not pay enough attention. There was no turbo failure - at least not since I own the car.

I suspected that scratches could come from burnet oil that build-up on pistons and head. Some of it could fall-off and get into rings/walls since it seems pretty hard. On the other hand, unburnt oil appears on one side only which discredits my theory since scratches are on all cylinders. I also thought about cylinders being out of round due to incorrect boring/honing without torque plate - we will never know.

All in all, I plan to keep this engine and car. You reassured me that it is worth to go with re-bore although its much more expensive.