What pistons are these?
 

Friend's '93 1.6.

Overheated badly due to a ruptured hose, warped the head.
The car had lousy power to begin with...

Head came off. Collapsed lifters and sunken valves seemed to explain the low power.
Then we noticed the pistons...

They look like an aftermarket low compression, oversize set.
Apparently, the car had sat for 8 years or so, and my guess is someone decided to rebuild the engine because the rings had stuck to the cylinder walls, causing damage.

The pistons are marked .50, but the bores measure less than 78.5 mm, (78.3 mm to be exact) which leads me to believe these are not the correct pistons for the B6 engine.
Someone found a set they could fit in the holes, and called it a day - that is my guess.

I now think these low comp pistons are not helping the performance, either.

So, do you recognize these pistons?


https://cimg1.ibsrv.net/gimg/www.mia...f49e2927cd.jpg


https://cimg2.ibsrv.net/gimg/www.mia...7b9329536b.jpg


https://cimg3.ibsrv.net/gimg/www.mia...b09a1aa8ea.jpg


https://cimg4.ibsrv.net/gimg/www.mia...63572ba491.jpg


Sorry for the crappy phone pics. They were taken in a hurry...

Not the best pic in the world, but they may be 323 Pistons.
https://www.enginepartsonly.com/1994...460-3/#gallery


Doesnt explain the discrepancy between quoted oversize, and bore size, but the crowns look about the same.

It's quite possible that either a previous shop used the lower comp 323 pistons, or a previous owner just swapped in an assembled 323 block because it was cheaper/easier.

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