Piston and Cylinder Condition Evaluation

[poroneday]

Well. I tore down my 3.0 in order to replace the lower head studs. I had four broken and one loose. While I was in there, I decided to put in new rings. Alusil cylinders but I was going to take the chance (no honing, just cleaning). When my Alfa buddy saw my pistons and cylinders he said something wasn't right. He said when he took apart his engine with 210k on it, the pistons looked brand new apart from the carbon build-up on top. He also didn't care for the light scratches on the skirts and the 12 o'clock and 6 o'clock position on the cylinders. So, I am hoping some experts on the forum wouldn't mind evaluating the pictures below on the condition of my pistons and cylinders. All of them pretty much look like the photos below. Having asked for the evaluation, be aware that my decision to re-use them has become a non-factor. While positioning the pistons for removal, I caught one of the skirts on the case and I broke it. So, it looks like she will be sitting awhile until the funds accumulate to buy new cylinders and pistons! Thanks for your time and input.

[Steve@Rennsport]

Hi,

You'll get plenty of opinions here, but I'd simply offer mine.

Alusils were an inexpensive solution for the factory at that time and were never meant to last as long as Nikasil ones do. It was a cost-control measure and most of them wound up in US cars.

The greatest area of piston wear occurs in the top ring land with the second ring land coming in well,..........second,...

Obviously, you'll not be able to reuse this set, however for future reference, the go, no-go decision is made after measuring all the ring lands to see if they are re-usable and to what degree. Needless to say, the ring lands MUST be free of all carbon and scrupulously clean to get accurate measurements.

At 210K, this is an opportunity to do a first-class rebuild so it will go another 200+ if you do this right and don't cut corners.

[poroneday]

Hello,

Thank you Steve for pointing out the importance of measuring all of the ring lands.

Just to clear one thing up, my friend's Alfa went 210k. Unfortunately, I am planning a quality rebuild at 142k. I brought up my friend's Alfa to compare how he said his pistons and cylinders looked compared to mine.

Is it typical for Porsche pistons to have the browning and build-up below the rings and around the piston pin hole? What about the light scratches on the skirt?

And on the cylinder, is it typical to see the polish and light scratching on the 12 o'clock and 6 o'clock position inside on the cylinder wall?

Are these normal looking worn pistons and cylinders or is something else going on with the engine that contributed to their appearance?

Once again, I am saving up for a full rebuild at this point so any answers won't effect what I am going to do. I am only asking so I can understand my Porsche, and Porsche traits, better.

Thanks again.

[burgermeister]

Pistons don't look too different from mine at 163K. Ring lands (and even ring gap) were all still well within spec. My Alusil cylinders had no scratching - many places still had crosshatching visible. I had lots of crusty deposits in the ring grooves, quite a bit more than yours - my oil rings had no visible spring spacer, it was just solid crud. Not having a spare $4K, and it being my own labor, I just re-ringed the pistons. 13K miles so far.

[Steve@Rennsport]

Originally Posted by poroneday

Hello,

Thank you Steve for pointing out the importance of measuring all of the ring lands.

Just to clear one thing up, my friend's Alfa went 210k. Unfortunately, I am planning a quality rebuild at 142k. I brought up my friend's Alfa to compare how he said his pistons and cylinders looked compared to mine.

Is it typical for Porsche pistons to have the browning and build-up below the rings and around the piston pin hole? What about the light scratches on the skirt?

And on the cylinder, is it typical to see the polish and light scratching on the 12 o'clock and 6 o'clock position inside on the cylinder wall?

Are these normal looking worn pistons and cylinders or is something else going on with the engine that contributed to their appearance?

Once again, I am saving up for a full rebuild at this point so any answers won't effect what I am going to do. I am only asking so I can understand my Porsche, and Porsche traits, better.

Thanks again.

Thanks for the correction on your mileage; I failed to see that in your posting.

What I see is fairly typical for engines with that kind of mileage. There are many variables at work here that include the oil one uses and how often its changed. Even the kind of air cleaner affects whether you see piston & cylinder scratching or not.

In short, what you see reflects maintenance.

[Eagledriver]

The coloring on the pistons is normal for Alusil pistons. They have a ferrous coating on them so they don't scuff the cylinders. The "clean" areas are where the coating has worn off. I've used Alusil on 2 race engines. In my opinion Alusil is underrated. I've seen minimal wear on any alusil cylinders I've had.

-Andy