Honing ALUSIL Blocks

SLOWESTN54

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Feb 9, 2021
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2007 E92 335i
Anyone here have any experience honing a Alusil Block. From my research it is possible, with using a AN-30 compound and felt pads. Just need to get the slighest scratches out of a cylinder and prep the block for new rings?
 

wheela

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Jun 4, 2021
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2015 e84 X1 35i Msport
You mean honing the LDS coating on the walls coated onto the Alusil of a b58 block?

Did you break a piston? Or just proactively building your motor😍😍😍
 

JohnDaviz

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Jan 6, 2019
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Here is what pro engine builder ChatGPT has to say:

If you’re just dealing with very light scratches in an Alusil bore and want to freshen it up in a DIY garage setup, you can skip the heavy industrial gear and go with a light reconditioning process focused on cleaning and re-exposing the silicon. Here's what you'd need:


✅ Light DIY Alusil Reconditioning Kit (Garage-Friendly)

🧰 Tools

  • Flex-Hone for Alusil (ball hone, fine grit ~240–320)
    • Brand: BRM (Brush Research Manufacturing)
    • Get one that matches your cylinder bore diameter
  • Variable-Speed Drill
    • Must be able to run at low RPM (~300–500)
  • Torque Plate (optional but good)
    • If you want to be precise

🧪 Chemicals & Supplies

  • Alusil-compatible honing oil
    • Light mineral oil or ATF works in a pinch
  • Alusil Etching Paste or Lapping Compound (optional)
    • To help bring out silicon particles
    • e.g., fine aluminum oxide paste or Glyptal style paste
  • Brake Cleaner / Acetone
    • For degreasing
  • Hot Soapy Water
    • Final wash to remove grit and particles
  • Lint-free cloths and paper towels

📏 Inspection Gear

  • Visual Inspection Light or Bore Scope
  • Dial Bore Gauge (only if you're checking geometry)

🛠️ Process (Short Version)

  1. Clean the bore with degreaser and inspect scratches.
  2. Light Flex-Hone pass (10–20 strokes per cylinder, low RPM, plenty of oil).
  3. Optional: Apply etching paste to expose silicon crystals.
  4. Brush finish if needed (hand brushing with Scotch-Brite or bore brush).
  5. Final Clean with hot soapy water → brake cleaner → dry with lint-free towel.
  6. Inspect surface – should have visible silicon and a light crosshatch.

⚠️ What Not to Do​

  • Don’t use conventional stones or aggressive abrasives.
  • Don’t remove too much material — it’s easy to go too far.
  • Don’t leave grit or residue behind — it’ll ruin your rebuild.

Want a shopping list with product links or part numbers?
 

SLOWESTN54

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Feb 9, 2021
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MANNN boys boys B58 is still running strong. This is for the X6m my dad bought. I assume it has a cracked piston ring. BADDD leakdown, slight scoring on the cylinder walls. Just Wanted to make sure the scoring out, before pulling the engine out.
 
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