How to Remove Steel Bolts From Aluminum Block

Written by mark o'brien
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Whether you are rebuilding an old engine or just doing some internal engine repair, you will need to get the engine block cover off. The engine block covers are bolted into place with up to 20 bolts sometimes. Rust, weathering and time can cause these steels bolts to be very hard to remove from the aluminium block. You should not just go banging away on the bolt or using an impact wrench as you may crack the aluminium block and then you have worse problems. Using a torch for heating the block is necessary to expand the aluminium to break the rust away from the steel bolt and allow you to easily unscrew it.

Skill level:
Moderately Challenging

Things you need

  • Safety goggles
  • Leather gloves
  • Heating torch
  • Wrench set
  • WD-40 spray

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  1. 1

    Spray a good amount of WD-40 on every bolt head.

  2. 2

    Light the heating torch. Begin to circle the bolt head with the torch heating the block around the bolt. Keep the flame about one inch away from the block for optimal heating. Try to avoid heating the bolt. You are trying to heat up the block and expand it away from the bolt; if you heat up the bolt you will expand it in the hole and make it even more difficult to remove the bolt.

  3. 3

    Heat the block around a bolt until it is orange to red in colour.

  4. 4

    Shut off the torch. Put the proper sized, closed-end wrench--so you don't strip the bolt head--onto the bolt. Unscrew the bolt counter-clockwise. Repeat this if the bolt does not come free. Repeat this heating process and unscrewing to every bolt holding the block cover on.

Tips and warnings

  • Wear safety goggles and leather gloves as the torch flame may create sparks.

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