I guess I should be more clear about my plan. I will polish the top 1/3 with the 3M polish and felt pads, in an attempt to replicate the process described by Sunnen. I'm doing this for two reasons: 1) the polish (either 3M or AN-30) and felt are available to everybody, and 2) it's much like honing a cylinder with stones, so everybody here should be able to do it. The middle 1/3 will remain untouched so I can get a handle on the morphology of the worn surface. The bottom 1/3 is the original factory finish because it's below the rings, so that's what we'll shoot for in the polishing step. Once the cylinder is polished, I'll cut up the cylinder so I can get it into my instrumentation. After I've examined the worn surface (middle 1/3), I'll send some of those pieces out to be cleaned and clean some others at home. If you guys have any other suggestions, let me know.

Furthermore, snowman will hone another cylinder with his silicon carbide grape hone and then send it to me.

Jack,

Do you need me to send another cylinder from this set to you?

Rondinone et al,
Great work! Although my deal for the used set of Alusils has stalled a bit, I'm still very intrigued with the progress. Rondinone, I think the 3M paste is a good alternative, being that it is readily available and presumabaly cheaper...why break the bank now? :-) I too was really encouraged about the industry standard for the surface of the bores and the very real possiblility of reconditioning a set of cylinders by merely re-establishing the surface within a comfortbale tolerance. Can't WAIT for the results. Who knows, this thread may come up in the next edition of BA's book (or Wayne's for that matter) taking a whle different position on re-using Alusils due to the great work done...

R/
Dustin

Rondinone, is it possible once you cut it up that you could send samples to William so that he can use his machine to compare cyls with the different mileage? William could you do the same? I believe the one William is using has 88K and the one you have Rondinone is 222K. I'd also be interested in knowing how the untouched finish below the ring wear surface compares. Theoretically they should be very close but it might be interesting to check. (variation in the original finishes could give us some idea of go/no go parameters) This way we would have data from two independent sources on the same samples.
Jack, do you know what knd of material the cylinder in the pics is? Thanks.

I also like the idea of trying to do it with readily avalible materials.
Remember, last summer I cleaned/polished mine with the scotch brite pad sandwiched between stones on an off the shelf 3 arm hone and the cylinder wall. It that time everything was a no-no. But I knew I had to try something for the rings to bite on.
What's the hardness of the material they use in the scotch brites anyway? It would be a hoot if it turned out to be simular.
Anyway anh911, Those P&C's are in my car that I have driven almost daily since the rebuild. Now about 3,000 miles ago.

If you want to send me something to test, I'm sure my freind Doug would be happy to do it. He may be lurking here anyway. I'm also trying to grow the audience.

Ok, so I guess that means you won't take one out and cut it up? ;)

Nope!

Is Charles still checking in? Charles, in your experience with refinishing niks how large have you successfully bored a 95mm cyl?

You guys are certifiably neurotic. Any competent pshchiatrist could probably diagnose your problem from this thread.

I love it and will check your findings regularly.

BTW, my used alusils have about 50K miles now since the rebuild and I actually do not ever need to check my oil (but I do, of course). They have about 235K miles altogether. Pretty hard working devices, considering the world regards them as useless, disappointing throwaway cylinders.

Amen, http://www.pelicanparts.com/support/smileys/pray.gif

I think the official term is alusilliosis...

Once I've had my look, I'd be happy to send the cylinder pieces out.

I just had a look through some of the scotch brite msds sheets (companies are required by law to reveal ingredients in their material safety data sheet (MSDS) so if you ever want to know the ingredients to a chemical product just look up the msds.). Some of those pads contain aluminum oxide, some contain plastic beads. Do you remember what type of scotch brite pad you used? It's possible it was abrasive enough to do the job. Certain aluminum oxides are very hard (corundum is one).

We're not neurotic, just cheap. I just bought the 3M polish and will get to work Saturday. I'll probably get a first look with the SEM on Monday.

Basic rule of thumb I like to stick by, as far as overboring cylinders, that the maximum that i'm comfortable doing is such that you are left with >= 1.5mm thick skirts. Some might say that's too thin, but as long as you're not doing anything too radical, or even a turbo, you're fine. We've had customers go as far as having 1mm thick skirts-- scary stuff, get the cylinders cryo'ed first. I would never try doing this with a stock cylinder, as the casting alloy mahle used had a yield strength of 36-42k psi, where our alloy we CNC specs out at 55-59k psi, and we do quality control checks with every batch from Alcoa. Having a better aluminum goes a long way.

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

If that 3M polish is a white paste, it is aluminum oxide. If so it is almost as hard as diamond and will even polish carbide tools. Only a diamond tool can be used to machine a solid piece of aluminum oxide, a very common substrate material for microwave thick and thin film circuits. Its also the material used in the vane type Air flow meters for the circuit board which contains the potentiometer. This type of circuit board is called a thick film board. Thick film refers to the thickness of the film depostited on the circuit board. A thin film is relatively thin and is usually etched off to produce a circuit as opposed to depositing a film to produce a circuit. In any case the alumina substrate is VERY stable at extreem temperatures, and immune to almost any sort of chemical attack, extreemly stable mechanically, in other words an almost ideal media to attach a circuit to that won't change under exteem conditions.

In its paste form, alumina oxide is almost a perfact sandpaper material. It is harder than most anything else, it is inert, it is non conductive. Thats about all I know about it. Except that the dielectirc constant is about 9.8 to 10.25 and the loss tangent is 0.001 and the coeffecient of expansion is about 6.5ppm per deg C about the same as Kovar,, and the change in dielectiic constant is about -90ppm per degree C. PS if you use my numbers for anything please double check them as they are off the top of my head and I have not used them in over 6 years.

Yes, see private e mail for address.:)

I just talked to my bro-in law and (without having a piston to confirm) he believes the ferrous coating is done with the anodizing process. He gave me the name of a shop to call monday and confirm, but thinks it's not a problem to apply to any pistons. Some considerations of the finished dimensions are necessary due to the thickness applied but it's doable. :D

I posted a WTB ad in the classifieds to try and find a spare set of cyls to bore out and use on my '89.

I'll send it out on Monday. Look for it around Thursday.

I called the US KS rep this afternoon and she is going to forward some questions to the field engineer in Germany but I need the OEM Porsche part number for the Alusils... Anyone have it or can look it up?

Nevermind I got it, Thanks

OK, here are some results.

First I set up a polisher using the Turtlewax cloth and a regular engine hone. The fabric was folded over and stapled in place in such a way as to allow the stone to flex as usual:

http://forums.pelicanparts.com/uploa...1074555812.jpg

Here's the polish also:

http://forums.pelicanparts.com/uploa...1074555843.jpg

I masked off the lower 2/3 of the cylinder:

http://forums.pelicanparts.com/uploa...1074555880.jpg

I polished the cylinder at about 100-150 rpm, one stroke per second or so. After 2 minutes there was significant metal on the hone:

http://forums.pelicanparts.com/uploa...1074555940.jpg

I wiped the cylinder clean, and examined it, and then decided to polish it for another 3 minutes. The cloths were considerable more dark afterward.

Then I cleaned the cylinder, wrapped it up in duct tape and stuffed a rag into it. I broke it up with a sledge hammer. Then it was time for SEM!

This is the factory finish at about 1000x:

http://forums.pelicanparts.com/uploa...1074556357.jpg

Sorry for the blur, the instrument was off and still wasn't completely warmed up. The islands are silicon particles (identified by elemental analysis). The relief is evident. According to my profilometer, the relief is a couple of microns.

Here is the worn area of the cylinder:

http://forums.pelicanparts.com/uploa...1074556536.jpg

That scratch is 20 microns across, and is easily visible to the eye.

Note how each particle has an area of wear underneath it. I'm not sure how to explain that. Here's a zoom:

http://forums.pelicanparts.com/uploa...1074556723.jpg

Those real bright objects are pieces of ring imbedded in the cylinder wall. The darker circular objects are pieces of silicon.

Here's another area:


http://forums.pelicanparts.com/uploa...1074556865.jpg

The dark island at the top left is a worn silicon particle. The mud-crack area in the center is aluminum. The debris to the right of that is a mix of silicon and ring material.

Here's the polished region:

http://forums.pelicanparts.com/uploa...1074557128.jpg

The round blob at the bottom (marked with a red 2) is a calcium carbonate particle. Calcium carbonate is added to motor oil to neutralize combustion acids.

It's obvious here that there is more texture. There's a silicon particle at the top left that is a little exposed. There is also significant pitting. Here's another:

http://forums.pelicanparts.com/uploa...1074557329.jpg

You can see alot of debris here. Most of it is ring material. Some of it is leftover polish (the quartz abrasive). There are tons of pits and holes. Here's a zoom on a pit:

http://forums.pelicanparts.com/uploa...1074557450.jpg

After having a look with the SEM, I put the pieces on my profilometer. My profilometer can also calculate the roughness (Ra), but all my numbers were lower than those posted above. Because the instruments are different, and mine's not set up specifically for testing cylinders, I wouldn't get bent out of shape about it. The relative numbers are what's important.

Factory finish: 0.26, 0.32, 0.17, 0.34. microns
Worn area: 0.095, 0.136, 0.12, 0.18 microns
Polished area: 0.37, 0.87, 0.40, 0.20, 0.13, 0.16, 0.31 microns

I took several measurements from different places.

Overall, the surface definately got rougher during the polish. A few things concerned me however:

1. There was alot of pitting. I know this cylinder has 220K miles, so I shouldn't be surprised. The pitting was visible to the naked eye (looks like darkness/roughness on the cylinder surface). I probably would not reuse a cylinder with pitting after seeing what it looks like at the microscale. Makes me feel better about getting those camshafts reground also!

2. I identified a bunch of leftover abrasive. It was everywhere, in pits, stuck to the surface, etc. Since so much is left over, I think that using the actual silicon abrasive (rather than silicon oxide, quartz, that is in the 3M polish) from Sunnen is probably better. There might be unexpected consequences of using quartz.

3. The polished surface looks nothing like the factory finish, due to the extensive pitting. But if we look past that, we can see improved relief of silicon particles (this was evident in profilometer also) in the polished area. Will that lead to improved ring break-in? It might.

This was only one experiment, and if I had to polish the cylinder again I would probably go longer. I didn't expect to see so much ring material left behind. It must really be lodged in there.

I didn't post all my photos, and the originals are much better quality (100k limit). I'm going to look all this over and think about it some more, and maybe even take another look in the SEM. I just learned that my own cylinders will need new rings. The compression was perfect across the board, but some of the ring gaps are too wide to warrant reuse.

Excellent information R, thanks. There might be some correllation to your ring gaps and the amount of ring material you found in those cylinders. The only way the gaps get big are if the ring wears or the cylinder does. (I know the cyl you are using for exp. isn't from your car) Can you measure one of the old rings' width to see how much it's worn? Seems like one key to a good job is getting most of the ring material off the cylinder surface.

Rondinone,

Is it possible to also post a macro view of the cylinder finish, one that shows the cross hatch that results from the circular and up and down movement of the polishing (honing) machine.

I realize this could be near impossible with the 100k limit. Possibly on someones web page?

You can email me high res pics of whatever and I can post them.

My direct email is jstgermaine@stgassociates.com

Hey R, how about a shot of the BFH smashing process... :)

Ha! I didn't record it because I knew you guys didn't have the stomach. As I swung the hammer I had this wierd daymare about accidentally grabbing the wrong cylinder.

I've been pondering this tonight, and I think that the real important information here is not what is shown, but what isn't shown. We know that traditional honing stones rip up the alusil surface making the cylinder unusable. This procedure didn't do that. And the profile numbers show that the polished area is about twice as rough as the non-polished worn area, so aluminum between the particles was removed. I
am going to think a bit more about this, and possibly examine some other areas of the cylinder.

Snowman, I didn't see anything like honing marks on these pieces. There were some scratches on the silicon particles but nothing like what's in the brush research literature (I've got it also). However, when I take photos of the cylinder you're getting I will be able to post them.

Ron..e "Ha! I didn't record it because I knew you guys didn't have the stomach. As I swung the hammer I had this wierd daymare about accidentally grabbing the wrong cylinder."

Sort of like taking a sledge to a Porsche, any Porsche yuck!!! Now I can't sleep, or eat, worse than the nightmare on elm st or any Gilbert Godfrey fling

I almost "reported this post to the moderator" as being unfit for viewing.:mad:

Awesome information Rondinone!

My Alusil rebuild is awaiting the final results (parts washer/ etching) before I go any further.

Thanks for the hard work to bust the myth and for the great information. Long Live the Alusil Revolution.

R, great work!
Someone above asked what Scotch Brite pad I used. It was the green pad without the sponge attached. Bought it at a grocery store. I used the same hone as R, but didn't wrap it, just sandiched it between the stone and the cylinder wall.
I know they make several different pads with different roughnesses.
I doubt it's the plastic balls because it definately scratches metal. When I clesn my stainles kitchen sink a new pat will certainly leave very fine scratches.

R, regarding the clogged up pores. The thought just came to mind that maybe the hone should be run in both directions. If the drill was reversed the particles in the compound might get in and clean some aeas that were not reached in the other direction.
How much ring material did you see in the worn cylinder. I sort of anticipated that the ring and piston material would be worn and deposited or clog up the pores.


Also good news about being able to plate pistons.

I just had my cylinders done by the Sunnen method. Cross hatches are clearly visible. (I will email JSG pictures)

If someone wants to send me a cylinder I could have it done by the 'official method' and returned for inspection.

PBH,

I can send you a cylinder from the same set Rondinone and snowman are experimenting with. When you email me the pics, send your shipping address along.

PHB, where did you get them done? How much?

I had a local (Toronto area) old-timer do them. He says he used to make a living doing Vega's 8 hours per day as he was the local expert and all the GM dealers brought their cars to him. He knew exactly how to do them as soon as he looked at them. He also does aircraft cylinders the same way.

He does them in about 5 minutes using the Sunnen method. He also did my heads and supplied new rings, and since I paid cash (guess why) I did not get a detailed bill. I believe he told me it was about $10 per cylinder (CDN funds), but I might be wrong.

I have received a LOT of help from this board over the past few years, I would be glad to have a cylinder done at my expense in return.

Old-timer's the best! That's a relative term.
My brother is 10 years my senior, just hit 51. He was wondering at what age old fart status turns to dried-up-old-fart. I told him it might be closer than he thinks. It ain't just the age it's the milege!

An 'old timer' is anyone ten years older than me.

A couple of thoughts have come to mind regarding the paste method. I noticed in the pic that it's labeled "fine" perhaps a more coarse variety (I'm assuming tht more coarse would mean larger particles of abrasive) would give us less of a polished finish and more the buff look we want. Also, wouldn't a wash-down with a good solvent after honing get rid of most of the left over polish? Finally, how about using a stiff sponge in place of the towels? The sponge would hold more of the paste. I recall one of the Sunnen or KS guides said to even apply honing oil while using the paste to aid the process.

I believe Sunnen uses felt.

Sorry, I wasn't clear in that last post. I meant to address it specifically to how Rondinone was testing.

If you want to stick with the 3M stuff? They make all sorts:

3M Compound Products

http://forums.pelicanparts.com/uploa...1074627754.jpg

For instance, on my car I used the microfinishing stuff, then the Perfect-It II, then the Imperial Hand Glaze (not pictured). All with a orbital waxer/polisher. Oh this was on the paint by the way......... :D

But my guess would be to try the microfinishing or ultrafinishing stuff for heavier cutting of the cyl. surface. Try the super duty stuff if you think it needs more? I was a bit leary using the microfinishing stuff on my paint, but it did a great job cutting thru the surface to expose fresher-looking and much brighter red paint. This is of course soft paint, not hard metal surfaces. Just saying that the microfinishing stuff has a pretty good cut to it.

You can get the stuff online if you can't source it locally.

HandsOnTools