Project GD Subaru STI, Building the Engine Part Five: Final Engine Assembly With IAG.

In our last story, you saw how IAG Performance assembled our short block with meticulous care. Now our engine travels to the second of IAG’s two cleanrooms for final assembly.

Read all about project STI and the other chapters of this engine assembly!

Our half-inch ARP studs are laid out on the bench.  Note that these are an IAG design with the proper end shape to fully bottom out in the blind case hole.  This is the best way to make studs and not too many on the market have this feature.

Assembly lube is applied to the case side threads.

The head dowel pins are tapped in place and the studs on the 4 outer corners are started by hand.

The studs are run down with an electric impact.

The two inner studs are started on the head gasket.


  1. I assume for the AVCS oil feed lines, the factory style screens are not used right? I only thought about that because the style of banjo fittings used have the bump on top, which for Subaru means they put a filter in there.
    I’ve always wondered how dirty the inside of the cam covers get over time.

  2. When do we finally get to see this bad boy on the dyno? What intake, what turbo, what exhaust, what blow off valve, what header? This is 5 months old!

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