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Another thing I noticed about the new crate engine were the partially threaded holes in each of the engine’s aluminum cylinder heads (arrows). A call to the Ford Racing tech line informed me that these were for use with what they call “thermactor tubes”. These tubes are used on vehicles fitted with emissions provisions but in off-road or pre-emissions usage they can be blocked using a plug set available through Ford Racing. I didn’t want to take the time to order the real plugs so I quickly fashioned some out of a quartet of 5/8-11x1-inch bolts.