{"product_id":"cat-c15-spacer-plate-6i4421","title":"CAT C15 Spacer Plate, 6I4421 | 3406E C16 C18, Std to .004 Under","description":"\u003ch2\u003e\u003cstrong\u003eNew CAT C15 \/ 3406E \/ C16 \/ C18 Steel Spacer Plate — 6I4421 | Standard \u0026amp; Undersize\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eRequired on every head job.\u003c\/strong\u003e The spacer plate sits between the block and the head, and it should be replaced with the head — not reused. We stock it in \u003cstrong\u003efive thicknesses\u003c\/strong\u003e: factory standard .338\" plus undersizes down to -.004\", in .001\" steps. Pick your thickness from the dropdown.\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eWhy Five Thicknesses? Liner Protrusion.\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe factory only made two sizes: standard (.338\") and .003\" under (.335\"). But the correct plate thickness depends on your \u003cstrong\u003eliner protrusion\u003c\/strong\u003e — how far the counterbore and liners sit relative to the deck. If the block deck or counterbores have been machined, a standard plate can leave the liner height out of spec, and that is how you crush a liner or lose a head gasket. The right undersize plate restores correct liner protrusion without cutting corners.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cp\u003e\u003cstrong\u003eStandard .338\"\u003c\/strong\u003e — unmachined deck, liner protrusion in factory spec\u003c\/p\u003e\u003c\/li\u003e\n\u003cli\u003e\u003cp\u003e\u003cstrong\u003e.337\" \/ .336\" \/ .335\" \/ .334\"\u003c\/strong\u003e — matched to how much has been machined off. Measure protrusion, then pick the plate.\u003c\/p\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eNot sure which thickness you need?\u003c\/strong\u003e Call us with your liner protrusion measurement and we will spec it — 832-894-3609.\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eThickness Options\u003c\/strong\u003e\u003c\/h3\u003e\n\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eThickness\u003c\/th\u003e\n\u003cth\u003eSize\u003c\/th\u003e\n\u003cth\u003ePart Reference\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eStandard\u003c\/td\u003e\n\u003ctd\u003e.338\"\u003c\/td\u003e\n\u003ctd\u003e6I4421\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e.001\" under\u003c\/td\u003e\n\u003ctd\u003e.337\"\u003c\/td\u003e\n\u003ctd\u003eAMK-1780\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e.002\" under\u003c\/td\u003e\n\u003ctd\u003e.336\"\u003c\/td\u003e\n\u003ctd\u003e6I4421-2A\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e.003\" under (factory undersize)\u003c\/td\u003e\n\u003ctd\u003e.335\"\u003c\/td\u003e\n\u003ctd\u003e1389381\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e.004\" under\u003c\/td\u003e\n\u003ctd\u003e.334\"\u003c\/td\u003e\n\u003ctd\u003e6I4421-4A\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ch3\u003e\u003cstrong\u003eFitment\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eCaterpillar \u003cstrong\u003e3406E, C15, C16, and C18\u003c\/strong\u003e engines, 1994–2012 applications. Send us your engine serial number if you want fitment confirmed before ordering.\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eOEM Cross Reference Numbers\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e6I4421 | 6I-4421 | 1389381 | 138-9381\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eComplete the Job\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eEvery head swap needs this plate plus a \u003ca href=\"\/products\/cat-c15-head-bolt-kit-1241854\"\u003e\u003cstrong\u003enew head bolt kit (1241854 \/ 1241855)\u003c\/strong\u003e\u003c\/a\u003e — bolts are torque-to-yield and single-use. Pair with the \u003ca href=\"\/products\/cat-c15-cylinder-head-2239250\"\u003e\u003cstrong\u003eC15 Universal Cylinder Head (2239250)\u003c\/strong\u003e\u003c\/a\u003e, or get everything in one box with the \u003ca href=\"\/products\/caterpillar-3406e-c15-c15-acert-cylinder-head-replacement-kit\"\u003e\u003cstrong\u003eC15 Cylinder Head Replacement Kit\u003c\/strong\u003e\u003c\/a\u003e.\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eHow do I know which thickness I need?\u003c\/strong\u003e\u003cbr\u003eMeasure your liner protrusion. If the deck and counterbores are untouched, standard .338\" is correct. If the block has been machined, match the undersize to what was removed. Call us with your measurement and we will confirm.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I reuse my old spacer plate?\u003c\/strong\u003e\u003cbr\u003eWe do not recommend it. The plate is a sealing and height-critical surface — replace it with the head so the whole stack starts fresh.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat did the factory offer?\u003c\/strong\u003e\u003cbr\u003eTwo sizes only: standard .338\" and .003\" under (.335\"). We stock the in-between and beyond sizes because real-world machine work does not come in .003\" jumps.\u003c\/p\u003e","brand":"TTM Diesel","offers":[{"title":"STANDARD .338\" (6I4421)","offer_id":44263415054548,"sku":"69-J6I4421","price":450.0,"currency_code":"USD","in_stock":true},{"title":".337\" — .001 UNDER (AMK-1780)","offer_id":48420855611604,"sku":"NA-AMK-1780","price":470.0,"currency_code":"USD","in_stock":true},{"title":".336\" — .002 UNDER (6I4421-2A)","offer_id":48420855644372,"sku":"NA-6I4421-2A","price":470.0,"currency_code":"USD","in_stock":true},{"title":".335\" — .003 UNDER (1389381)","offer_id":48420855677140,"sku":"NA-1389381A","price":470.0,"currency_code":"USD","in_stock":true},{"title":".334\" — .004 UNDER (6I4421-4A)","offer_id":48420855709908,"sku":"NA-6I4421-4A","price":470.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0671\/9927\/1124\/files\/360466_G.png?v=1721071475","url":"https:\/\/ttmdiesel.com\/products\/cat-c15-spacer-plate-6i4421","provider":"TTM Diesel","version":"1.0","type":"link"}