Comp's fourth most popular cam, the 277LR HR-113, idled at only 10.75 inches in our 6.0L test engine. With the stock GM LQ9 truck short-block and stock cast pistons with shallow valve reliefs, piston-to-valve clearance was right on the edge, only about 0.050 inch. That was enough to scrape by on the dyno, but we wouldn't want to rely on going that tight for real-world use...so you're looking at a set of custom, aftermarket, forged, deep-notch pistons to really make this setup run safely with about 0.080/0.100-inch intake/exhaust valve-to-piston clearance.

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