{"product_id":"cummins-isx-head-bolt-kit-3678506","title":"Cummins ISX Head Bolt Kit, 3678506 \/ 3678804 | ISX15 X15, New","description":"\u003ch2\u003e\u003cstrong\u003eCummins ISX \/ ISX15 \/ X15 Head Bolt Kit — 3678506 \/ 3678804, New\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eOne kit covers every ISX ever built.\u003c\/strong\u003e Cummins never changed the head bolt spec: from the first 1999 dual overhead cam ISX through the 2026 X15 — CM570, CM870, CM871, CM2250, CM2350, and the latest CM2450 — these are the same bolts. Whatever year your truck is, this is the kit.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eRequired on every head job.\u003c\/strong\u003e ISX head bolts are torque-to-yield — they stretch permanently when torqued and are single-use by design. Reusing stretched bolts cannot hold spec clamping force, and the usual result is a blown head gasket within months.\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eKit Includes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cp\u003e\u003cstrong\u003e(22)\u003c\/strong\u003e Hex flange head cap screws — OEM# \u003cstrong\u003e3678506\u003c\/strong\u003e\u003c\/p\u003e\u003c\/li\u003e\n\u003cli\u003e\u003cp\u003e\u003cstrong\u003e(4)\u003c\/strong\u003e Cylinder head bolts — OEM# \u003cstrong\u003e3678804\u003c\/strong\u003e\u003c\/p\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003e\u003cstrong\u003eStandard or Cryo Treated\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cp\u003e\u003cstrong\u003eStandard\u003c\/strong\u003e — precision-machined to OEM specifications, heat-treated for strength\u003c\/p\u003e\u003c\/li\u003e\n\u003cli\u003e\u003cp\u003e\u003cstrong\u003eCryo Treated\u003c\/strong\u003e — cryogenically processed to relieve residual stresses in the fastener for added fatigue resistance. For high-cylinder-pressure, fire-ringed, and high-horsepower builds.\u003c\/p\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003e\u003cstrong\u003eFitment — Every Generation, 1999–2026\u003c\/strong\u003e\u003c\/h3\u003e\n\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eEngine\u003c\/th\u003e\n\u003cth\u003eYears\u003c\/th\u003e\n\u003cth\u003eGenerations\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eISX (dual overhead cam)\u003c\/td\u003e\n\u003ctd\u003e1999–2010\u003c\/td\u003e\n\u003ctd\u003eCM570, CM870, CM871\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eISX15\u003c\/td\u003e\n\u003ctd\u003e2011–2017\u003c\/td\u003e\n\u003ctd\u003eCM2250, CM2350\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eX15\u003c\/td\u003e\n\u003ctd\u003e2018–2026\u003c\/td\u003e\n\u003ctd\u003eCM2350, CM2450\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp\u003eSend us your engine serial number if you want fitment confirmed — but on this kit, the answer is yes.\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003ePairs With\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cp\u003e\u003ca href=\"\/products\/cummins-isx15-cylinder-head-4374091\"\u003e\u003cstrong\u003eCummins ISX15 \/ X15 SOHC Cylinder Head (4374091)\u003c\/strong\u003e\u003c\/a\u003e\u003c\/p\u003e\u003c\/li\u003e\n\u003cli\u003e\u003cp\u003e\u003ca href=\"\/products\/5406187-cummins-isx15-head-gasket-set-4376104-2881767\"\u003e\u003cstrong\u003eISX15 Head Gasket Set (4376104)\u003c\/strong\u003e\u003c\/a\u003e or \u003ca href=\"\/products\/5406187-cummins-x15-head-gasket-set-upper-gasket-set\"\u003e\u003cstrong\u003eX15 Upper Gasket Set (5406187)\u003c\/strong\u003e\u003c\/a\u003e — for head-only jobs; in-frame overhaul kits already include it\u003c\/p\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eCan I reuse my old ISX head bolts?\u003c\/strong\u003e\u003cbr\u003eNo. These are torque-to-yield bolts — they stretch permanently the first time they are torqued and cannot hold spec clamping force a second time.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill this fit my year?\u003c\/strong\u003e\u003cbr\u003eYes. Cummins used the same head bolts on every ISX, ISX15, and X15 from 1999 through 2026, across every generation from CM570 to CM2450.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhen is the cryo kit worth it?\u003c\/strong\u003e\u003cbr\u003eFire-ringed heads, high-horsepower builds, and engines that run sustained high cylinder pressure. For a stock rebuild, the standard kit is the right choice.\u003c\/p\u003e","brand":"TTM Diesel","offers":[{"title":"STANDARD","offer_id":44073757966548,"sku":"ISXHBK","price":360.0,"currency_code":"USD","in_stock":true},{"title":"CRYO TREATED","offer_id":48420974952660,"sku":"ISXCHBK","price":615.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0671\/9927\/1124\/products\/040116_01_XL_600x_4852cd2e-8f87-4529-9c7d-0df3fdd6e86b.jpg?v=1699332789","url":"https:\/\/ttmdiesel.com\/products\/cummins-isx-head-bolt-kit-3678506","provider":"TTM Diesel","version":"1.0","type":"link"}