Aluminum block honing
 

Hi

I didn't find any pics of aluminum block honing in this forum,
so here are some.

Honing this blocks is a 4 stage process.
this are the stones used for the first 3 stages.

http://i1133.photobucket.com/albums/...e/DSCF0003.jpg

Left to right:
Course stone (first stage)
medium stone (second stage)
polishing stone (third stage)

http://i1133.photobucket.com/albums/...e/DSCF0004.jpg

This are the felts for the 4th stage
Sorry, i don't have any new ones on hand right now.

http://i1133.photobucket.com/albums/...e/DSCF0005.jpg

The silicone paste used in the 4th stage.

http://i1133.photobucket.com/albums/.../DSCF00073.jpg

A pic of the block in the honing machine.

http://i1133.photobucket.com/albums/.../DSCF00013.jpg

A cylinder just after starting the honing process.
Notice the wear ridge from the first piston ring, also faintly visible the one from the second ring.

http://i1133.photobucket.com/albums/.../DSCF00133.jpg

http://i1133.photobucket.com/albums/.../DSCF00352.jpg

Cylinder after the first stage.
Most of the material is removed at this point.
0.08 to 0.1 mm remains in the cylinder.

http://i1133.photobucket.com/albums/.../DSCF00143.jpg

http://i1133.photobucket.com/albums/.../DSCF00342.jpg

After the second stage.
About 0.02 mm left.

http://i1133.photobucket.com/albums/.../DSCF00153.jpg

http://i1133.photobucket.com/albums/.../DSCF00302.jpg

After the third stage (polishing).
Notice the reflections in the cylinder.
Hone marks are still visible.
Cylinder is at final size.

http://i1133.photobucket.com/albums/.../DSCF00193.jpg

http://i1133.photobucket.com/albums/.../DSCF00232.jpg

After the 4th stage.
Cylinder is finished.
Reflections and hone marks are gone.
The surface is dull gray and featureless.

http://i1133.photobucket.com/albums/...e/DSCF0002.jpg

4 cylinders in 4 stages of machining.

That is cool, thanks.

I always believed you wanted the crosshatching per your stage 1 photos.

On cast iron cylinders you shoot for about stage 2, but not on this aluminum ones.

Great photos! Thanks a bunch for posting.
I really did not know the repair process for the aluminum cylinders. The photos really show the patterns with good detail.Are you a tech at a dealer, indy, or?

I did some engine rebuild mani years ago when I lived in California,
but I still have the equipment.
Got hold of a damaged 560 block, that I could mess up for this thread.

Do you intend to rebuild this engine? I ask because MB has a special process for their aluminum bores. While I don't understand all of the nuances it is my understanding that the castings have a high silicon content. For the surface finish the aluminum is chemicaly etched leaving a predominately silicon surface for the rings to wear against. That is how Mercedes gets such an unusually long service life from such a soft material.

FWIW, when BMW first tried to build its aluminum V8, it failed miserably. I've seen those with 10K mi and completely worn out bores.

No ,I am not rebuilding this engine.
I just got my hands on a junk block.
See my thread:
http://www.peachparts.com/shopforum/tech-help/310618-another-reason-change-your-timing-chain.html
It's the same block.

The process shown is the one that Mercedes recommends to re bore this blocks.
The 4th stage removes a few thousands of a mm of aluminum from the cylinder walls, leaving the silicon behind.
This is done by rubbing the silicone paste into the cylinder wall, using the felts instead of stones in the honing machine.

I assumed those were liners. Is that just the block material we are looking at? How common are unlined aluminum blocks?

All 116 and 117 alu blocks, and to my knowledge all 119 blocks are unlined.
Liners are available for repair purpose.
112 and 113 blocks are made from "normal" aluminum and have alusil liners.