WOW, this discussion went on longer than i thought. You guys busted out almost as much scientific data as the eram discussion brought every engineer from the cracks in the wall. My cylinders were shipped out today, i'll post a pic of what the walls look like. (they are redone KS cylinders)

Viva la revolucion`http://www.pelicanparts.com/support/smileys/2ar15.gif

Let us know who did the work when you post the pics.
(what's wrong with brown??)

Did you get my address? Haven't heard from you yet.

Sorry for the delay in shipping these cylinders out guys. I left for the east coast last week and just returned late Saturday evening. Jack, I sent you an email, I'll finally get that cylinder off to you tomorrow.

PBH, you have mail.

The AN-30 arrived today. I'm going to take one of my jugs into work tomorrow and get a baseline on the profilometer. I'll probably polish it tomorrow night. Woo hoo!

It's more abrasive than the 3M polish, as I can feel the grittyness with my fingers. It will definately cut deeper.

It says "please see instructions included with Sunnen felt set" on the can. Of course.

ha ha ha, what are the odds? But surely we have enough documentation on this process by now?

Can't wait to see the before and after shots.

whoa, this is really getting good! I can hardly wait for the results...if nothing else, it gives al the Alusil believers out there more to base their faith upon...:-) ANH911...any word on the re-plated pistons? just think...3.2l Alusils!

R/
Dustin

haven't had a chance to talk to any platers yet. I'll try tomorrow.

Still no time to talk to the platers. Been a busy week. But regarding the stock "ferrocoat" that KS uses: it's actually iron and tin plating. The skirt is done with iron and the rest of the piston is plated with tin to prevent corrosive action between the aluminum and iron. They plate everything, ring grooves, pin bore etc.

I've polished two cylinders with the AN-30 so far. This time I used a turtlewax miracle towel cut and wrapped around my honing stones. First I polished for two minutes at 150 rpm, 0.5-1 stroke per second. The profilometer recorded a texture about 1/2 as rough as the factory. So I polished it for 3 minutes more, and this is the result:

Cylinder #3, not yet polished:

http://forums.pelicanparts.com/uploa...1075342012.jpg

Cylinder #2, polished:

http://forums.pelicanparts.com/uploa...1075342103.jpg

Cylinders 2 & 3 looked roughly the same before I started. Cylinder 1 looks just like cylinder 2. When I run my fingernail down it, it feels like a real fine chalkboard. The shiny area around bdc could probably be used as a guide. It started out shiny and got progressively duller. It's still a bit more shiny than the rest, but I suspect it's pretty worn compared to the rest of the cylinder.

I measured the ring gap before and after polishing, and it increased by ~0.001", which increased the bore by 0.001/6.28 = 0.00016 ". That's about 4 microns. I hope I didn't overdo it.

I'll drag cylinder 1 back to work tomorrow and get another reading.

From what I've been told about this process you might have overdone it. I think my guy does them for about 30 sec. I'll get a picture of mine posted in a few days. Work/family are seriously interfering wiht this thread.

I recieved a package from Bernd W. on Friday.
It was mailed from the "Netherlands".
It contained a hard copy of the "Reconditioning Aluminum Blocks" pamphlet. (A link to a PDF is posted here on page 4.)
He also sent some cylinder pictures. (microscope)

I also re-read the Sunnen directions on page 7.
There is also a link to Sunnen there which has their cataloge with their "portable hone" the portable hone is described as one option in the directions.

The KS describes lapping for 60 seconds with 15 strokes.
(This is for the final finish after 2-3 steps of honing oversized.)
Not necessarily the same as reconditioning as is being attempted here.

Sunnen directions is really the final process as well and stated 1-1/2 minutes with the portable hone equipt with the felt pads.

With the automatic machine it is set to shut off in about 2 minutes.

I just wanted to condense that info here.

I also noticed something that is probably a long shot.
KS does/or did supply oversized pistons for the 928. (Reconditioning pamphlet)
The diameter is 95mm and 95.5mm for oversized.
928S is 97mm and 97.5mm for oversized.

I did a few searches yesterday for some spacifications on the 928 to hopefully see a set of pistons and fins all the dimensions.

The only thing I found was set of 4 on e-bay (4 doesn't make sence)
Anyway they were flat top pistons.
Anyone know anything about the 928 pistons please speak up.
I know this is a long shot, but worth a look.
I would think it's possible that a set of oversized 928 pistons or standard or oversized 928S pistons might just work.

One thing I did find is that there seems to be a lot less info out there on the watercooled p-cars than 911's.







928S is listed

After thinking it over, I'm not too concerned about the amount of time spent polishing. The sunnen hone shown in their catalog is really robust unlike my little spring loaded junker. It likely applies much more pressure, and can do the deed in less time. I'm sure my felt is softer also.

Doubters behold, for I have provided proof. These are profilometer readings of my number 2 cylinder before and after polishing with AN-30.

Worn areas:

Note the large difference in X and Y axes. The surface isn't really this rough.

These are two different areas.

http://forums.pelicanparts.com/uploa...1075417451.jpg

http://forums.pelicanparts.com/uploa...1075417466.jpg

Polished:

This is near the top of the cylinder. The plateaus are silicon particles sticking out of the aluminum wall. Remember the X axis is compressed. The particles are actually much wider.

http://forums.pelicanparts.com/uploa...1075417598.jpg

This is the shiny area at BDC after polishing. Not as rough as above, but the particles are still evident. Most importantly, it's not a mirror finish any longer.

http://forums.pelicanparts.com/uploa...1075417650.jpg

For comparison, here's the factory finish before any polishing was done:

http://forums.pelicanparts.com/uploa...1075417685.jpg

The depth between particles for the factory finish, and most of the polished areas are about 10 microns.

FYI, these cylinders had 115k before teardown. I'm feeling more confident that this is going to work.

Excelent info as always Rondinone!

Im still anixously awaiting the results of any etching and or grape honeing procedures.

Great work, excellent post as always. I was looking for some more info and ran across these pics. They show the hone w/felt pads and an30. They appear to be brushing the silicon paste onto the cylinder wall, not applying it to the hone. I don't recall reading that anywhere in the docs that we have but I'll go back and review.

http://forums.pelicanparts.com/uploa...1075441758.jpg

FYI I have seen the Sunnin felt pads. They are VERY robust pads. NOTHING WIMPY about them. No way can any home brew stuff come close to the pressure these pads must apply. Think about a soft STONE hone rather than anything felt, ie a very robust felt pad, fully packed to the brim with honing material, and then pushed until the stone (silicone paste) oozes out due to pressure during honing.

But to put this in perspective, no significant material is removed during this process, eg no more than one or two tenths of a thousandth of an inch for up to several minutes of honing.

This also consistant with some very trick plateau honing stuff I have seen for the Sunnin hone. EG brushes, nylon brushes, so stiff you could polish stainless with them, combined with some sort of soft stone material.

All this is escencially the same as the silicone grape (dingle ball) hones in practice in my opinion. In other words everyone has finally DISCOVERED plateau honing and invented their own way to do it, better or differen't than the other guy.

anh911, using the brush is there in the documents I pointed to yesterday, somewhere.

Rondineone, just to get into perspective on your scales can you convert 500 microns to something I can draw a comparison to?
Please excuse my ignorance, I'm not from a remote backwards area, but I have no way to measure that small and asside from the ocassional discussion like this I don't use it.

In other words I know it's smaller than a "nat's ass".
How many microns in a inch or mm?

Thanks for all the hard work!

Sorry. I know most people are used to inches, but we conduct our work only in metrics.

Micron is short for micrometer. One micron is one millionth of a meter, or one thousandth of a millimeter, or approximately the size of a bacterium. Three of these scans were 0.5 mm long, one was 0.7 and the factory one was 0.2 mm. The vertical axis is -10 to 10 microns, which is just under one thousandth of an inch (25.4 microns per 0.001 inch). It seems like that's a short distance to check, but there's really alot of information present. These scans are conducted by dragging a fine needle across the surface, so a profile represents a short straight line on the cylinder wall. Since the X and Y axes are different scales, if you want to visualize what the surface really looks like you would have to stretch out the horizontal axis by a factor of 25, i.e. the particles are 25x wider than they look here.

I applied the AN-30 to the cylinder wall like they suggest.

Did you get that cylinder yet Jack?

Unfortunately he hasn't yet.:(

Although I promised to send Jack and Paul a cylinder, I have been absolutely swamped. I will make an effort to get them both out either today or Monday at the latest.

Sorry for the delay all....

Thanks for the conversion.
It was about what I expected, but just wasn't sure.
In the pictures that KS sent with the book (Simular to yours with the microscope) Bernd identified a scratch. It's hard to tell if it was a tooling mark from a hone or an imperfection.

When looking at your microscope pictures how does that scale compaire?
Thanks again.

78-89 3.3 turbos had 97mm pistons, but I think they were just for Nikasil. would they be coated or plated? I wonder what compression they would create with the short stroke SC crank?


I saw a set of 993 pistons on e-bay for +-400 maybe.
Those are 100 mm. That would be too big?

The turbo pistons don't have the correct coating but are too low compression to be of use to us unless you are converting to forced induction.

From what Bernd told me the 100mm (as used) are too big, he said the cylinders would go out of round quickly once the bore got that big (the walls would be too thin). That's one of the reasons the 3.6 has larger head bolt spacing.