gcb951

Hey,
I'm looking for a Sunnen AN cylinder hone tool. It's the kind that you use with a normal electric drill. If anyone has one I would be happy to buy it or rent if from them for a reasonable price. I would buy the new stones and paste to do the silicon/aluminum coating, you wouldn't have to worry about me wearing out your stuff if anyone is willing to rent it out. I am an honest person and I am not looking to steal anything from anyone. I just want to get my cylinders honed and start rebuilding my damn car so I can get it up and running for this spring/summer. Please let me know if you can help. Thanks.

xsboost90

NOOOOOO. dont hone the cylinders in a 944 engine. From what i understand its aluminum coated in a "nickisile"? coating. If you hone them you chance screwing up the coating and then the block is junk. If you have decent cylinder walls w/ no deep scratches that you can feel w/ your finger nails just run with it. This is what ive heard, seach further before you hone it out.

Mighty Shilling

What Dan said.

David Floyd

Guy's, it can be done at home with the correct parts.

There is someone on the list that loans or rents the hone and pastes, I will try and locate the post for you gcb951

500

I've always wondered about this (the final step, the felt with the paste step...). Always did seem like something that could be done at home. I too would be interested to hear about this.

Thanks!

Variance

Dan,
The cylinders are "alusil," an aluminum/silicon composite. You can hone the cylinders, you just need to finish up with a special paste that eats away the aluminum, leaving the silicon behind. From reading gcb's post, he knows this and will get the required materials.

Edit-Typos

Granite 944

I too would be interested in hearing how this all works out. I just figured the tooling neccessary to do this would be much to cost prohibitive for the home type mechanic to aquire, and thus, be pretty much a machine shop procedure only. It would really be interesting info to me to find out that this can be correctly "final honed" properly, at home.

Zero10

This could be a good thing. So many people just re-ring without honing, and most machine shops won't hone the cylinders unless they are perfectly round and straight. It's kind of a middle-ground for budget rebuilds.
I am interested now!

Mongo

You need a very special stone to hone the alusil bores of a 944 engine.....ask me how I know?

Kevin Baker

I too would be interested in finding out more about this, as I currently have an early block that is begging to be worked on as a "back up".

WolfeMacleod

After reading some things about Alisul and honing on Pelican and other places, I sent an email to Bill Burris on the PCA website. He's the guy who answers 944 technical question.

I'd asked about honing, and mentioned that eventually the time would come to rebuild.

Here's his reply.

Answer:
Here's the scoop:

Alusil isn't a plating or a coating, it's the aluminum/silicon alloy that the entire block is made from. This is an extremely durable material that has served Porsche well for years. The secret to the processing of this material is in the etching of the cylinder bores. If you can imagine how the etching process works on a microscopic level, an acid is used to break down the aluminum in the cylinder walls, exposing a very thin, very hard layer of silicon (this is the silicon related to diamonds, friends, not the stuff that comes out of the tube or featured on Pamela Anderson.) The hard silicone surface is what the rings ride on. The gaps between the silicone particles where the aluminum used to be fills up with oil and keeps the rings in good shape.

If someone was to try hard enough with a hone to get past the silicone and dig all the way down to the original alusil, you'd have an engine that ate itself in short order; lack of lubrication and direct contact with the aluminum will eat the rings in short order.

My experience with high mileage blocks, both 944 and 928 (same block materials and processing) is that they look almost good enough to eat off of. The shine on one of the 928 blocks torn down after high mileage testing still looked like glass it was so clean.

Damage to individual cylinders can still be repaired. Consider using pros that have the Sunnen machines to do the job right; photos of the appropriate equipment can be seen at http://www.928motorsports.com/services/uschrome.html

Bill Burris - PCA WebSite - 12/22/2005

David Floyd

anything you ever wanted to know about our block types.

http://www.msi-motor-service.com/dow...ren/alu_en.pdf

Mongo

guys just a quick FYI on our engines...the bores CAN AND WILL GO OUT OF ROUND towards higher mileage requiring a bore.....think 2.7L (104mm) '89 pistons bore

500

David,

Thanks for that link, it is great.

What I'm really curious is that fourth step, the lapping with the paste. In my situation, the block is in great shape in terms of bore wear, out of round etc. I paid a very reputable shop to measure each cylinder (after having the girdle torqued on) to be sure about this. There does not seem to be any reason to bore the block oversize. However, it seems to me, that the lapping with the paste is way best prepares the surface for the new rings to set in.

Lots of people seem to re-ring these engines with no prep to the cylinder walls, and it seems to work OK (it seems).

But if there was a way to have this step done myself, I would be excited. Failing this, I will likely try to search out a shop with the pads and paste to have it done.

Jfrahm

Ugh. Email him back and tell him it's sili-con not sili-cone. Sheesh. And yes all that info was right here on the forum also without so much of the silicon (glassy stuff) and silicone (caulk, fake *****) confusion.

And as for comparing it to diamonds, don't. Diamonds are pure carbon in a snazzy crystal structure. Silicon Carbide is probably what he is thinking about, which is tough and a great abrasive but as a crystal it is known as Moissanite, which can be used as a substitute for a diamond until your fiancee has her ring appraised.

-Joel.