▁fifty - se ven ▁minutes , ▁and ▁fifty - five ▁seconds . ▁ ▁Due ▁to ▁a ▁then - stru gg ling ▁economy , ▁both ▁Ford ▁and ▁Che v ro let ▁cut ▁back ▁on ▁factory ▁support ▁for ▁the ▁ 1 9 7 1 ▁NAS C AR ▁W inst on ▁Cup ▁Series ▁season . ▁NAS C AR ▁would ▁also ▁limit ▁engines ▁in ▁the ▁aer od ynamic ▁su pers pe ed way ▁cars ▁to ▁ 3 0 5 ▁cub ic ▁inches ▁starting ▁in ▁this ▁race . ▁ ▁Race ▁report ▁Def ending ▁NAS C AR ▁Grand ▁National ▁West ▁series ▁champion ▁Ray ▁E lder ▁won ▁the ▁race ; ▁making ▁it ▁the ▁first ▁time ▁that ▁the ▁ 5 0 0 - mile ▁event ▁at ▁R ivers ide ▁was ▁won ▁by ▁a ▁manufact urer ▁other ▁than ▁Ford . ▁The ▁average ▁speed ▁was ▁ ▁while ▁the ▁pole ▁speed ▁was ▁. ▁This ▁race ▁was ▁the ▁final ▁NAS C AR ▁Cup ▁Series ▁event ▁with ▁triple - digit ▁number ed ▁cars ; ▁with ▁three ▁of ▁them ▁qual ifying ▁for ▁the ▁race . ▁( K ittle kow ▁# 1 0 7 , ▁Sch illing ▁# 1 4 8 , ▁Collins ▁# 1 7 7 ). ▁E lder ▁became ▁the ▁first ▁winner ▁in ▁NAS C AR ' s ▁" mod ern " ▁history . ▁ ▁Only ▁ 1 1 ▁cars ▁finished ▁this ▁ 5 - hour ▁mar athon . ▁The ▁ 8 th - place ▁finish er ▁was ▁ 2 2 ▁la ps ▁down , ▁and ▁the ▁ 1 1 th - place ▁finish er ▁dropped