{"product_id":"gsc-power-division-k-series-30mm-31mm-exhaust-valves-set","title":"GSC Power-Division K-Series 30mm \u0026 31mm Exhaust Valves","description":"\u003cul\u003e\n\u003cli\u003eSwirl-polished heads for airflow \u003c\/li\u003e\n\u003cli\u003eBack-cut design for reduced weight \u003c\/li\u003e\n\u003cli\u003e3D design for superior strength \u003c\/li\u003e\n\u003cli\u003eVersatile 30mm and 31mm options \u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003c!-- split --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli\u003e\u003ca class=\"active\" href=\"#Description\"\u003eDescription\u003c\/a\u003e\u003c\/li\u003e\n \u003cli\u003e\u003ca href=\"#VehicleFitment\"\u003eVehicle Fitment\u003c\/a\u003e\u003c\/li\u003e  \u003cli\u003e\u003ca href=\"#TechnicalData\"\u003eTechnical Data\u003c\/a\u003e\u003c\/li\u003e  \u003cli\u003e\u003ca href=\"#InstallGuide\"\u003eInstall Guide\u003c\/a\u003e\u003c\/li\u003e \u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\n\n\u003cli class=\"active\" id=\"Description\"\u003e\n\u003ch3\u003eGSC Power-Division Exhaust Valves - 30mm Standard \/ 31mm Oversize - Honda\/Acura K-Series\u003c\/h3\u003e\n\u003cp\u003eA K-series exhaust valve does its job in one of the worst spots in the engine. It's hit with hot exhaust gas every time it opens, it slams back onto its seat thousands of times a minute, and on a boosted engine it's fighting pressure in the exhaust manifold too. The factory valves were built for stock power. Push past that, and the heat starts to warp the valve head slightly out of shape. Once that happens, it can't seal cleanly on the seat. You lose compression a little at a time, and leakdown numbers creep up until you finally go looking for the cause.\u003c\/p\u003e\n\u003cp\u003eGSC designed these valves with CAD and computer simulation to keep their shape under heat and load. That way the face stays flat against the seat and keeps sealing. They come in two head sizes. The 30mm is the same size as stock and drops into a factory head. The 31mm is an oversize valve for a ported head that can use the extra flow. Will they make power by themselves? Not much. What you're really buying is a valve that keeps sealing when the engine's working hard, which is the part that counts on a built motor.\u003c\/p\u003e\n\u003ch4\u003eBack Cut and Swirl Polish\u003c\/h4\u003e\n\u003cp\u003eA back cut is a small angle ground into the back of the valve, just above where it seals on the seat. It smooths the turn the exhaust gas has to make as it gets past the valve, especially in the first fraction of a millimeter of lift. That's where a valve flows the worst. It also takes a little weight off the valve. The heads are swirl polished too, so the backs are smooth and the flow comes off them cleanly. The stems are micropolished, so they slide in the guides with less friction and don't hold onto oil.\u003c\/p\u003e\n\u003ch4\u003eTwo Finishes\u003c\/h4\u003e\n\u003cp\u003eThe black nitride valves are nitrided all over. Nitriding is a surface-hardening treatment that helps the stem and face resist wear over time. They're sold as a set of 8. The polished chrome version comes in the same 30mm and 31mm sizes and gives you a hard chrome surface on the stem for wear in the guide. Those are sold individually, so you'll need to order 8 for a full set. Both are made from a modified stainless steel built to handle heat. For most boosted and high-RPM street builds, that's plenty. If you're running a lot of boost on a car that sees long, hot sessions, look at an Inconel valve for more heat margin.\u003c\/p\u003e\n\u003ch4\u003eThe Tips\u003c\/h4\u003e\n\u003cp\u003eThe rocker arm pushes on the very top of the valve stem, called the tip, every time the valve opens. A soft tip wears and changes your valve lash. GSC hardens the tip or caps it with a Stellite wafer. Stellite is a very hard cobalt alloy that's welded on and holds up to wear far better than plain steel. GSC also sets the tip height so your valvetrain geometry stays correct without stacking up shims to make it work.\u003c\/p\u003e\n\u003ch4\u003eInstall Notes\u003c\/h4\u003e\n\u003cp\u003eThe 30mm valves fit factory seats, but any new valve still needs a seat cut or a valve job so it seals properly. The 31mm valves are a different job. The seats and port have to be machined to take the bigger head, so this is head-porting work for a machine shop, not a valve swap. With either size, measure installed spring height on every valve, and replace the stem seals while the head's apart. If you're adding cams or RPM, it's the right time for new guides and stiffer springs too.\u003c\/p\u003e\n\u003ch4\u003eFitment\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003eHonda\/Acura K-series engines - confirm your exact engine code before ordering\u003c\/li\u003e\n\u003cli\u003e30mm: standard size, fits factory exhaust seats\u003c\/li\u003e\n\u003cli\u003e31mm: oversize, requires machining the seats and port\u003c\/li\u003e\n\u003cli\u003eBlack nitride: sold as a set of 8 \/ Polished chrome: sold individually\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\n \n\u003cli id=\"VehicleFitment\"\u003e\n \u003cspan class=\"tag\"\u003e2002-2006 Acura RSX \u003c\/span\u003e\u003cbr\u003e\u003cspan class=\"tag\"\u003e2002-2006 Acura RSX Type-S\u003c\/span\u003e\u003cbr\u003e\u003cspan class=\"tag\"\u003e2004-2008 Acura TSX \u003c\/span\u003e\u003cbr\u003e\u003cspan class=\"tag\"\u003e2003-2007 Honda Accord \u003c\/span\u003e\u003cbr\u003e\u003cspan class=\"tag\"\u003e2002-2006 Honda CR-V \u003c\/span\u003e\u003cbr\u003e\u003cspan class=\"tag\"\u003e2006-2011 Honda Civic \u003c\/span\u003e\u003cbr\u003e\u003cspan class=\"tag\"\u003e2006-2011 Honda Civic Si\u003c\/span\u003e\u003cbr\u003e\u003cspan class=\"tag\"\u003e2002-2005 Honda Civic Si\u003c\/span\u003e\u003cbr\u003e\u003cspan class=\"tag\"\u003e2001-2005 Honda Civic \u003c\/span\u003e\u003cbr\u003e\u003cspan class=\"tag\"\u003e2003-2011 Honda Element \u003c\/span\u003e\u003cbr\u003e \n\u003c\/li\u003e\n\n\n\n\n\u003cli id=\"TechnicalData\"\u003e\n\n\u003c\/li\u003e\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\u003cli id=\"InstallGuide\"\u003e\n\n\u003c\/li\u003e\n\n\n\u003c\/ul\u003e\n","brand":"GSC Power","offers":[{"title":"30mm \/ Nitride","offer_id":69632486506530,"sku":"GSC-2041-8","price":203.42,"currency_code":"USD","in_stock":false},{"title":"31mm \/ Nitride","offer_id":69632486539298,"sku":"GSC-2043-8","price":127.53,"currency_code":"USD","in_stock":false},{"title":"30mm \/ Chrome","offer_id":69632486572066,"sku":"GSC-2041-01","price":26.27,"currency_code":"USD","in_stock":false},{"title":"31mm \/ Chrome","offer_id":69632486604834,"sku":"GSC-2043-01","price":16.54,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/2218\/5701\/files\/14549894.jpg?v=1793823816","url":"https:\/\/www.hybrid-racing.com\/products\/gsc-power-division-k-series-30mm-31mm-exhaust-valves-set","provider":"Hybrid Racing","version":"1.0","type":"link"}