The standard pistons I've seen look pretty smooth from what I remember, yours looks like it's been painted with hammerite. I suspect det. or maybe a bad case of porting sand

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If at first you don't suck seed, try drier grain.

I’ve got pictures of the pistons from when I pulled the head off back in 07 and the finish to the pistons then are exactly the same as they are now, plus I’ve also got pictures of my 182 pistons and they also have the same finish, surely if it was det then the smooth machined part of the crown would also show signs of det too?
What I have noticed which you can see in the side on picture of the piston is the lack of carbon staining on the rear of the top land indicating how much piston rock I’ve had in the bore and couple this with the poor state of the cylinder walls, I think the land has grabbed the wall and just given up the ghost whilst being abused.
Don, I’m really pleased on how the block has turned out and I plan to keep this standard up throughout the whole rebuild, I’ve done plenty of rebuilds in my time but this will be by far the biggest project I’ve under taken as it’s the whole car that is getting sorted and not just the engine. Dorris

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Black CS 2771

I've never seen new pistons with a pock marked surface on their crowns. The only marks I have ever seen on new piston crowns are milling marks. Also, I wouldn't necessarily expect the det marks to be uniformly distributed over the entire surface of the piston crown.

From your description it sounds like the engine(s) may have been run on cheap fuel. When I ran my standard ST205 on 95 octane fuel a few years ago when I was skint the knock sensor/ignition retard protection was working overtime. This was a completely standard car with no boost controller or any other mods.

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Don
GT4DC Chairman
1994 Toyota Celica GT-Four ST205WRC JDM 269bhp @ 0.9bar
1994 Toyota Celica GT-Four Special GT 590bhp @ 1.8bar
1989 Van Diemen RF88/89 Formula Ford 1600
2008 Nissan Patrol GU 3.0L ZD30DDTi 154bhp

Just had a quick look at the pistons in a 185 bottom end I'm currently stripping and they do indeed have markings as above, except mine also have deep pitting in the usual 2 places, looks more like debris than det.
The 205 standard pistons are smooth as per my memory.

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If at first you don't suck seed, try drier grain.

Chris is there any chance you can get a picture of your pistons up just to compare. Dorris

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Black CS 2771

These are what brand new ST185 pistons look like.

What I might do is check the ring gap of my originals and compare it to what it is supposed to be, should give me an indication on how worn everything is. D

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Black CS 2771

I believe they're bad castings as I too can't imagine how the macined parts are damage free

Dorris,
They don't look like std Toyota pistons. They don't have the Toyota size markings and the pitting/finish is much much rougher than Toyota piston.

I will go find some std St185 pistons (toyota supplied) and take a pic when I get a chance.

Only pic I have so far..

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JP
GT4DC Treasurer

Grey St185 RC
Silver BMW E46 M3
Multicolour yawn Honda VFR400
Silver Honda Civic Type-R

This is after a quick brush up with wire wool over part of it.

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If at first you don't suck seed, try drier grain.

Chris, What is that around the inlet valve area - looks like det marks to me?

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Kris
95 ST205 - slept for 10 years, now waking up...
Avensis
http://www.gtfours.co.uk
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Turbocharging - the replacement for displacement

Looks more like foreign objects to me. The edges of the craters are sticking up in the air, plus a bit big for det. Also score marks on the side of the piston above top ring.

Suspect it's had a turbo let go at some stage.

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If at first you don't suck seed, try drier grain.

JP. Those look like 205 pistons in your pic.

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If at first you don't suck seed, try drier grain.

Oh Ok. They came out of a 1993 ST185 JDM engine. Very late spec but not a CS/RC.

It could be that they had been swapped at some point.

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JP
GT4DC Treasurer

Grey St185 RC
Silver BMW E46 M3
Multicolour yawn Honda VFR400
Silver Honda Civic Type-R

Got the remains of the engine and transmission out yesterday that is now sat in the garage waiting to get cleaned and sorted. Boy wasn’t it a heavy lump! Something that did surprise me though was how light the CS bonnet is for a steel one, maybe that effin great hole might have something to do with it lol. Projects rolling along nicely now time to go and spend some money on bearings and seals. Not sure what to do about the flywheel though. Dorris

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Black CS 2771

Is the flywheel damaged or are you wondering if its worth replacing it with a lightweight flywheel? Having driven a GT-Four with a lightened flywheel I would say that its worth doing as the engine seems to spin up much more readily and is fun to drive, especially ona sprint/race track. On the other hand if you plan on just using the car for the daily commute you'd probably be better off keeping the standard flywheel as the engine will be more tractable at low revs in stop-go traffic.

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Don
GT4DC Chairman
1994 Toyota Celica GT-Four ST205WRC JDM 269bhp @ 0.9bar
1994 Toyota Celica GT-Four Special GT 590bhp @ 1.8bar
1989 Van Diemen RF88/89 Formula Ford 1600
2008 Nissan Patrol GU 3.0L ZD30DDTi 154bhp