Valve clearances weren't just in tolerance they were all exactly to manufacturer specs accurate to 0.001"

Seats werent re cut or replaced they were just OEM subaru ones. They were however reground by hand to seat the valves properly.

With regard to cams. Valves don't just snap shut, they physically can't. The cam will slow the closing speed of the valve just before it gets to the seat.

Supertech have confirmed by email that a higher spring rate would not lead to failure as I asked that question.

But they've also said that one of their valves wouldn't just fail like that. Although plenty of failures on Nasioc tell a different story.


To answer a few questions I seem to be getting:

Yes I am going to rebuild it.

No it wont be run with lesser power, if anything I'm going to throw more boost through it.

And yes it will be hammered down the drag strip again when it's built.

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605whp
Quarter Mile in 10.9 seconds @ 135mph /217kph
0-100 kph 3.2 seconds