BTR Truck Norris Cam, Springs and Hats 12613412 The blow off valve operates

The blow off valve operates by eliminating the pressure spike that occurs when closing the throttle suddenly at high rpm and/or boost

you cannot mill your cylinder heads without the possibility of needing to flycut your pistons

The reverse flow and pressure creates havoc with the turbo or blower by attempting to stop or even reverse the compressor wheel (not desirable at 50

then added a single S475 Borg turbo

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BTR Truck Norris Cam, Springs and Hats 12613412 The blow off valve operatesBTR GEN III & IV LS TRUCK NORRIS CAM Specs: 212 22X, . 552 . 552, 107 LSA INTAKE LOBE LIFT @ TDC: 0. 05271 The Truck Norris will deliver a roundhouse kick in the pants to your 1999 2013 Silverado or Sierra. Developed from hundreds of hours of in house cam lobe design and dyno testing, this camshaft has more power and torque everywhere in the curve compared to our legendary V2 truck cams.