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Heads-off Gaskets OnWith the heads gone, we got a look at the stock head gaskets. These composition gaskets are fine for a stock powerplant, but they can easily fail in high-boost applications if there's even a hint of detonation. We sent them to Clark Copper Head Gaskets to duplicate them in copper. Note the OE flat-top 10.4:1 pistons with intake valve reliefs almost ready for the scrap heap: We already had a set of Wiseco forgings one size over with extra-thick crowns capable of machining for reduced compression if required. Toyota permits one size overboring.