Re-ring Alusils?

[Rondinone]

I should add, that I am unclear about how this cylinder was treated. What exactly was done to it?

BTW my alusils are 12k miles and counting, running great.

[ironhorse]

Thanks for the return PM and posting the results here, Alan.

You guys did a great job of digging below the surface and enlightening the rest of us with your findings.

[Porsche_monkey]

Originally Posted by Rondinone

I should add, that I am unclear about how this cylinder was treated. What exactly was done to it?

BTW my alusils are 12k miles and counting, running great.

I provided the cylinder to Adam, so let me provide some more detail....

The cylinder was donated by another Pelican so I can't comment on the mileage, but it was a well used cylinder.

I took the cylinder to my local 'engine rebuilder' who used the 'Sunnen honing method' on the cylinder. I believe this involves an oil/grit lubricant to expose the silicon on to surface again.

The shop I used was an approved G.M. repair depot for Vega engines when they had Alusil issues, and he still does air cooled aircraft engines.

He re-did my 2.7 cylinders for me a few years ago, the car ran really well when I finished. Unfortunately I sold it before I ever accumulated any significant mileage, so I do not know how long it would have lasted.

Gee, where is Snowman?

[ironhorse]

Originally Posted by Porsche_monkey

... The shop I used was an approved G.M. repair depot for Vega engines when they had Alusil issues, and he still does air cooled aircraft engines ...

Is it possible that you could to share the gentleman's contact info (either on the forum, or via PM) ?

[Porsche_monkey]

Originally Posted by ironhorse

Is it possible that you could to share the gentleman's contact info (either on the forum, or via PM) ?

I am sorry to say he had a stroke in the summer and had to stop working.

[very~worn~944]

A post from the dead! I had many questions that caused me to read all 565 posts in this topic.

At this point I am getting ready to try a hybrid method following these posts to my 944 turbo block...... ........IN THE VEHICLE.

I have some cylinder stain from coolant sitting on the piston (I know, I know: ha,ha- he has to deal with coolant) and some scoring on another cylinder. I was going to try a soft brillo-like pad to clean up the score mark a bit. Then I was going to use the home-hone AN-30 paste method to "polish" a new silicone surface. I am planning on using new gotze rings. The block has 145,000 on it and if I fail I am only back to the same spot (minus rings, rod bearings, and gaskets).
I will post an update when I get there...but for now I am on a search for AN-30 compound!

[Rondinone]

I ordered it directly from Sunnen. Good luck, let us know how it works.

[HondaDustR]

Hehe...look what I have!

Never before seen in captivity.



Same here. I decided to formulate a "hybrid" technique to refresh my cylinders for my current rebuild. I'll be using Deves rings in mine.
I'm going to get a standard 3 arm drill hone, tape over the stones with duct tape, wrap them in felt, wet them and the cylinder down with 20 weight non-detergent straight mineral oil, and try honing with the AN-30 paste. I have my bad block to do some trial runs on first just to see what it does. I already cleaned my cylinders with super clean and a scotchbrite. They are a nice bright grey color, but still mirror smooth. I'll post back with the results as well.

[HondaDustR]

As promised, here's the post from my project thread over on the 944 board.

Here's the hone.



OK, honing was pretty interesting. Mostly R&D today. The paste straight out of the can is pretty thinck and needs some oil to dilute it down a little. I found the best way is to liberally smear oil on the cylinder and then smearing some AN-30 paste on top of that before it has too much of a chance to run down the cylinders. Work it into the oil on the cylinders and it thins nicely. Use enough so you get an even brown coating that almost hides the cylinder surface. Also, the new felt needs to be oil soaked first, then some paste worked into the felt.

The cylinders were initially prepped with a scotchbrite and purple power scrubbing straight up and down with very light pressure to avoid scratching the surface, rinsed and dried. The first run, in cyl 4, the paste was a little too thick and I ran the lightest stone pressure I could for 80 sec. It seemed to clean the walls pretty good, but not much else. The second run, in cyl 3, I ran less paste with a little more oil and max stone pressure for 90 sec. Seemed to dull the finish somewhat, and felt slightly rougher than the untouched cylinders, but still on the ineffective side. I ran the 3rd run in cyl 2 with more paste, but thinned like I had it in the second run, max pressure, and 160 seconds. Not much different that the second run.

lightly scrubbed, not honed. Notice how shiny it is on the bottom section below the rings. The upper part of the cylinder is also pretty reflective, but not quite as bright silver colored. There is no wear ridge I can feel, but it might measure out on a micrometer. It doesn't really feel any soother or rougher than the rest of the cylinder.



3rd run. There is a more even and dull grey finish. It feels slightly rougher than the unhoned cylinder, but is still pretty smooth.



I wasn't too impressed with the results. They looked certainly better than nothing, but I was hoping for more. I decided to go at it with the scotchbrite on the last cylinder. I scrubbed nice and hard for about 2 minutes total, putting a fine crosshatch pattern in the cylinder. It was making grey soap suds, so it was definitely taking something off. Here's the cylinder after scotchbrite.



Then honing. I prepped the cyl for honing as for run 3. I also realized I needed to have the hone running faster, ~230 rpms and ~80 strokes per minute, rather than 80 rpms and 230 strokes per minute... (c'mon!). I honed for ~90 seconds. The cylinder looked much more like what I was after! The scotchbrite crosshatch marks were nearly gone but still noticable on close inspection, the cylinder was a dull grey that was finally not reflecting things clearly, and definitely felt somewhat rougher.

Now we're getting somewhere!


Compare to run 3.



Another view. The 4th run pic is slightly out of focus on the cylinder area, but it still doesn't exaggerate the difference by much.






The plan now is to develop a 2 stage honing process, first with scotchbrite pads and purple power, and then with the AN-30 and felt as done on the 4th run. I'm just going to start back at cyl 4, and just have to figure out about how long is good to run the scotchbrite pads. The cylinders on the new block should break in the new rings pretty well now.

[safe]

Is the Sunnen compound etching?

I talked to a 944 guru and he said the alusil was ok to re-ring and "hone" as long as you used an etching compound to eat away at the aluminum, leaving the silicone crystals exposed.

[HondaDustR]

I don't know exacty, but "etching" sounds like a chemical removal of the aluminum, and lapping, as it is called in the 944 factory service maunal, is removing the aluminum abrasively. Either way, it does the same thing...remove the aluminum from the very surface exposing the silicone particles.

I believe the AN-30 is a mild enough abrasive that it wears away the aluminum without affecting the silicone particles. Sunnen actually makes honing stones that accomplish the same thing now. They have a flexible substrate and the correct abrasive that allows the abrasive to work around the silicone particles and remove only aluminum. The AN-30 and felt hone is apparently old school.

I also think that's why it worked so much better when scoured with the scotchbrite pad first, since it seems to be abrasive enough to skim off the surface of the cylinder, exposing fresh material, which then laps with the AN-30 correctly. I'm sure you can do the same thing with the correct honing stone, but it would be alot easier to not take too much off and not tear up the surface using incorrect pressure, grit, type of stone, etc. with the scotchbrite.

[HondaDustR]

OK, X-post on the final development and implementation of the scotchbrite + AN-30 honing. I'll post back with results once the motor is running and has some miles on it.

Originally Posted by fast924S

I built my motor, did about everything you can do without droping serious money, Only things I left out was crank work and serious head work, I bumped CR from 9.5 to 10.2, Race valve job, Port matched everything,. Plus some extras. I love the way the motor runs, I didnt hone the cyl, I was told do this only if you have large scratches in the cyl wall, On these engines its ok not to see cross hatch marks, just a dull gray. You dont need to go to crazy on Performance stuff, The gain is very minimal unless you go crazy. Safe the extra cash and do suspension mods... Trust me

Did you put new piston rings in the old cylinders?

I did work on the scotchbrite honing today. Overall, I'm happy with the results. I did have a couple scratches in the cylinders deep enough to catch a fingernail. The scotchbrite hone obviously did not remove them, but they no longer catch a fingernail, so...

I also determined it worked best when lubed with mineral oil instead of degreaser. I couldn't tell much of a difference, but the oil honed one looked a little cleaner and more consistent. It also worked best at minimum pressure set on the hone and run at ~120 rpms 80 strokes/min for about 45 seconds. It's also crucial not to extend out of the cylinder too far or the extra pressure of the stones concentrated at the edge will take more off than the middle. It definitely leaves a fine crosshatch surface. One guy on the 911 rebuild forum said he honed his cylinders for new rings with only the scotchbrite pads attatched to a glaze hone and his rings broke in just fine. I found the surface comes out a bit better when honed with the felt and the AN-30 after the scotchbrite. I also found that doing the AN-30 honing as described above twice seemed to smooth out the scotchbrite crosshatch marks a little better than just once. With all that in mind, I did manage to successfully hone all 4 of the cylinders on my good block with my developed method. The surface is a nice smooth matte finish that has kind of a micro-rough fell to it. There are still faint crosshatch marks, but that probably can't hurt and might help.

The scotchbrite hone. I used 2 sewing pins for each one to hold the pads on, same as with the felt.


Here's after 45 sec of honing. There's a little aluminum material in the oil but not much.


Here's the scotchbrite finish. It's very fine and it made kind of a grey rough finish. It would probably work fine, but of course I've got to be all high tech about it.


AN-30 paste and oil ready for felt honing.


Here's what I get after one AN-30 honing run. The crosshatch marks are still detectable, but not as "sharp" looking.


Ok, enough screwing around! Let's get to the point. Here's the cylinders on the good block. they are actually in much better condition than my old one. Fewer scratches and virtually no wear ridge at the top. The old block had a very small one.


I found out that cutting off the leading corner of the felt helps it not to fold under the pads while honing. Be sure the pads are pinned up very tightly around the stones. They will want to spin around the stones and will get all bunched up, or even put the pins onto the cylinder wall if they are not tight. There my be a better way to attach them, but this is what I had for now.


The last cleaning before assembly. It is crucial to clean ALL the AN-30 out of every nook and cranny. There was a bunch that ran down all over the crankcase area. I pretty much did a full cleaning/flushing the oil galleries again just to be sure.


All done and ready for pistons, crank, final assembly, etc. These were all done with 1 45 sec. scotchbrite run and 2 80 sec. AN-30 runs. I just have to set ring gaps and get the crank ready. Hopefully this will break in the rings, actually have 100% compression, and will last a long time again!

[1990C4S]

I had mine done by a shop in the area that seems to know what they are doing. They looked pretty much like that. My guess is that with NEW rings and a proper break-in you will be fine.

[HondaDustR]

SWEET! I'm really looking forward to seeing how it runs. I've heard running it hard right away as soon as it warms up is the best way to break in rings, so that's what I'll do. Various rpms...hard up to 5000 or so, on and off throttle with high rpm coasting mixed in to help suck the oil up through the rings for lubrication and clearing out the metal from the rings wearing in.

[schpenxel]

Time to bring back the dead....

Here is a PM I received from HondaDustR that I felt gives a very good summary of the process. This is what I will be doing on my BMW N62 block.

I ended up honing for around 60 to 90 sec using green scotchbrite scouring pads wrapped around a standard 3 arm spring hone and lubricated with non detergent 20 weight oil. I can't remember exactly how long the duration was, but it was around that time. You want to deglaze the cylinder but not take any more material than necessary. The honing speed was roughly 60 rpm, but I was just using a hand drill. You want to make roughly 30-45 degree intersections with the honing passes and be careful not to extend too far past the edges. Keep the hone moving in and out as long as it is rotating. Squeeze the arms together when inserting or removing the hone. What you want to see is a clean etched looking cylinder with very fine surface scratches. Be sure to thoroughly clean the cylinders before lapping.

For the lapping with AN30, be sure to thoroughly prime, or really, impregnate the felt pads with AN30 and oil before starting, because it won't really do much until the pads are saturated. The AN30 is kind of thick and needed to be diluted with oil for me. I just used 20 weight non detergent oil. Smear the cylinder liberally with oil and then add AN30 until it makes a mixture thick enough to not run too easily, but not so thick that the hone pads skim over the paste without lapping the cylinder. It takes a little bit of trial to find the best mixture. Lap at about the same speed as before for about 2 min. The lapping process is more or less self limiting, so a little extra isn't the end of the world if you have to kind of get the hang of the process. After you're done, triple wash the entire engine block with a good cleaner like super clean or purple power. I used mr clean magic erasers to scrub down the cylinders to ensure that there was no grit left behind. The cylinders should look and feel kind of like a chalk board...kind of a dull grey with a sort of micro-rough texture. You may see some remaining marks from the scotchbrite deglazing. That's not a big deal. You must deglaze with scotchbrite. The AN30 by itself is ineffective on used cylinders.

I broke in on straight 30 weight conventional for the first 100 miles, just 10w-40 conventional changed at 1500, 5000, and went to synthetic after that. Very important! ! You MUST drive it like you stole it right away as soon as it warms up. 90% of the ring seating on alusil is in the first 100 miles, so you must roll on the throttle hard to about 80% of redline, and then close the throttle and coast to make the engine vacuum draw oil past the rings to flush the wear particles away. Full throttle pulls from the bottom of 2nd or 3rd, combined with some general hard on and off throttle. Once you get past about 30-50 miles, start running longer and harder stints revving out closer to redline. You need that high pressure behind the rings to bed them in while the little silicon particles on the cylinder surface are still sharp and fresh. Once they're worn smoother, the wear reduces substantially, and you have a very durable cylinder. This quick break in is especially crittical for re-lapped used cylinders as the geometry may not be perfect and may require a little extra ring wear to seat.

Personally, I have almost 60k miles on my rebuild and I still get about 2000-3000 miles per quart oil consumption. For the first 20k or so, the oil consumption was negligible. Compression has been good, around 160 psi, but the valves and associated top end is not in the greatest shape lately, as they were used as is for the rebuild. Woem valve guides, probably needs seats re-cut as well, but it still runs great and still my daily driver with 210k miles.

[KTL]

Here's a video from the guy who literally "wrote the book" on the Sunnen honing process

https://www.youtube.com/watch?v=-ek5qv8Nmg0

I'm sure if you called him up, he'd be glad to share some tips. Nice guy who really knows his craft.

Sending him some cylinders would be quite easy (compared to shipping an engine block) and I bet he'd also mount them with a torque plate to simulate the installed condition of the cylinder before honing.

[schpenxel]

Unfortunately the engine I'm working on doesn't make it possible to ship just the cylinders.. wish he was on the opposite coast for sure, as I am in NC.

I will give him a call though if I have any questions. I wish I had called him prior to ordering the Sunnen stuff, as he probably could have sold me a smaller quantity of the compound and his felt pads for a lower price and offered more information than them.

[schpenxel]

Alright everyone--here are a few pictures from today. Luckily I had an old block to play with, so I came up with a few different times/speeds to try

-----

First try of the day, about 30 seconds, relatively slow speed on drill. Ignore the crack at the bottom. That's why this is a test block afterall

#1






#2--went a little longer on these and I think my pads got dirty as the scratches look deeper to me



#3--this is where I went all out, higher RPM on the drill, and well over a minute for sure. It was the last one I did as well, and I noticed some silver'ish color on the pads that I think I really should have been keeping clean.



And lastly, this is a view from underneath for what I thought were the best ones

[HondaDustR]

I have a feeling you schotchbrited dry. ? Make sure to use lots of oil on the cylinder. I haven't read my posts in a couple years.. these pictures are a good comparison for what you want. Re-ring Alusils?

These specs are what you want now that I've properly refreshed my memory. 45 sec, minimum hone tension, ~120 rpm for scotchbrite, followed by two AN30 runs, ~80 sec each, high hone tension, cleaning and applying fresh paste mix for each 80 sec run, same rpm, but search for my rebuild thread for the whole enchilada. I dont have the link handy atm.

[safe]

Looks way too rough and shiny.
From what I gather, alusil should not have any cross hatching.