Want to push big power from your EJ20?

To produce reliable power, a Closed Deck Block is the only way to go!

An inherent issue with the open and semi-closed deck EJ20 blocks are the cylinders flexing under high power levels, causing a wide range of issues. Check out our article on deck designs  if you want to know more about open, semi and closed deck block variations. The solution is a Closed Deck Block, which provides support around the top of the bore. Unfortunately, the factory produced EJ20 Closed Deck Blocks are becoming very difficult to find in usable condition. Possum Bourne Motorsport have designed and developed a CNC program to close deck EJ20 blocks. PBMS recommend moving to a closed deck 2.0 if targeting in excess of 330kw/450hp at the wheels.


  • Reduced deck flex - improving cylinder head and gasket sealing
  • Reduced liner flex -  reducing liner movement and cracking
  • Improved cylinder support - maintain bore shape and aid piston sealing
  • Using an MY98 EJ207 will give the ability to have a closed deck block with a rear-thrust crankshaft. These have a larger thrust bearing surface for better bearing life, and will accept a stroker crankshaft for larger displacement.


We have the CNC program to close deck EJ20 blocks with the following casting numbers. Please contact us if you have another block, so we can develop a CNC solution to suit your needs.

  • T20C

Note: We have also developed a 2.5L variation to suit EJ25 Blocks as found here.


  1. Book a CNC Close Deck modification with PBMS
  2. Deliver stripped and cleaned block halves to PBMS
  3. Fit block halves to machining fixture
  4. Machine block for Closed Deck Plate
  5. CNC machine Closed Deck Plate
  6. Insert Closed Deck Plate into block

To complete post modification (Not included in price)

  1. Machine bores to suit pistons
  2. Calculate cylinder deck heights and have decks machined accordingly
  3. Thoroughly clean block halves before assembly

Please note: This is a process that can only be performed with the engine fully disassembled, so we recommend doing this at the time of an engine rebuild. The prices indicated are for the modification to the block halves only and do not include remove, stripping, cleaning, deck surfacing, assembly of the engine or any other components in the photo. PBMS takes no liability for an engine we do not inspect or build from start to finish. We recommend taking measurements and checking the block suitability prior to Close Deck Modification.



  • EJ207 CNC Closed Deck Modification.
  • Recommend for above 330kw/450hp (At the wheels)
  • Designed to strengthen an EJ207 block for high power reliability.
  • Discuss the suitability of this modification for your engine, please contact us.


SKU 1808
Brand PBMS
Shipping Weight 25.0000kg
Shipping Width 0.500m
Shipping Height 0.500m
Shipping Length 0.500m
Shipping Cubic 0.125000000m3

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