How to Smooth Exhaust Manifolds

(Instructions for EW Smoothing Kit, Part # 46076)

Important Safety Guidelines

  • 1. Wear eye protection such as our full-face mask (13123) or goggles (43090) at all times when using carbide burrs or abrasive rolls.
  • 2. Always wear a properly fitting Dust Mask, like our Buff Shop Dust Mask (13000).
  • 3. It's better to scrape away old gaskets that may contain asbestos than to use abrasives on a power tool. This will reduce the likelihood of getting asbestos particles in the air.
  • 4. Do not wear loose fitting clothing. If your hair is long, tie it back.
  • 5. Clamp manifold firmly to a bench or place it securely in a vise.
  • 6. Use minimum pressure against abrasive for longest life and to avoid bending mandrels.
  • NOTE: Do not use abrasive rolls or carbide burr in excess of 22,000 rpm!


  • 1. See owner's manual for proper procedure for exhaust manifold removal.
  • 2. Degrease the manifold with a heavy-duty degreaser such as Eastwood's Metal Wash (10120), or PRE painting Prep (10041z).
  • 3. Wear disposable gloves, like our Disposable Nitrile Gloves (43098), to avoid contaminating the cleaned surface.
  • 4. Examine the manifold for the obvious defects, such as a pinholes, warpage, or cracks. Replace or repair defective manifolds before smoothing.

    Using a Carbide Bead Burr (Comes with Deluxe Kit):
    A carbide burr can speed your work by quickly leveling the rough pits or casting flash. Keep the spinning burr moving when in contact with the surface to avoid creating an uneven surface. Exercise care not to cut through the casting wall on older severely rusted manifolds.

    TIP: If you are using a pneumatic die grinder, regulate the air pressure down to the desired speed so that the trigger can be completely depressed, assuring a secure grip and better control of the tool.

    Using Abrasive Rolls

    Smooth the manifold using the die grinder with the included 4" mandrel and 80-grit cartridge rolls and tapers. If you used a carbide burr to begin the smoothing process, work the 80-grit cartridges at about 90 degrees to the previous burr scratches.

    TIP: Using 60-grit flap disks on an angle grinder can speed up smoothing on large, flat surfaces and curves. They are available through Eastwood in 4-½ "(19055) sizes.

    NOTE: Exercise care to avoid damage to gasket surfaces. Caution: If the old gasket material contains asbestos, use paint remover and scrape by hand to prevent asbestos from becoming airborne. Dispose of asbestos material in accordance with local regulations

    NOTE: If you plan to match the cylinder head exhaust port to the gasket size: current high performance engine building practice indicates the exhaust manifold opening should be larger than the cylinder head exhaust ports to create a step that inhibits exhaust gases from flowing back into the combustion chamber. The Eastwood Porting Kit (46056) provides complete details.

    Once the pits have been smoothed out using the 80-grit cartridge rolls, go over the 80-grit scratched at right angles with the 120-grit abrasive rolls until all 80-grit scratches are removed and blend in surrounding area.

    Final Preparations for Coating:
    Any remaining rust can be removed by abrasive blasting or soaking in Fast Etch or Eastwood Rust Dissolver .

    TIP: If you wish to impart a natural rough sand cast look to the smoothed surface, try this technique: use a piece of 36 or 40-grit sand paper to hold against the surface and gently hammer to transfer some roughness to the surface.

    NOTE: If using rust remover, be sure to check manifold every 20 minutes and remove rust remover when part is rust free. Leaving manifold in contact with rust remover longer than necessary will damage the manifold.

    Wash manifold with PRE Painting Prep (10041Z) and allow to dry before coating. Follow directions on the can of high temperature manifold coating for satisfactory results. Eastwood provides durable manifold coatings in three colors: Satin Black (10393Z), Stainless Steel (10394Z), and Factory Grey (10395 Z)