▁in ▁order ▁to ▁distinguish ▁the ▁engine ▁from ▁the ▁usual ▁ 3 . 0 ▁L ▁engine ▁and ▁it ▁also ▁featured ▁hand ▁pol ished ▁and ▁port ed ▁in let ▁and ▁exhaust ▁ports . ▁Only ▁ 2 5 0 ▁R S ▁ 3 1 0 0 s ▁were ▁produced ▁for ▁hom olog ation ▁purposes , ▁making ▁original ▁ 3 . 1 - lit re ▁engines ▁very ▁rare , ▁although ▁modified ▁engines ▁b ored ▁+ 0 . 6 0 ▁are ▁common , ▁one ▁of ▁the ▁first ▁ 5 0 ▁engines ▁which ▁was ▁in ▁a ▁R S ▁ 3 1 0 0 ▁that ▁was ▁free ▁for ▁car ▁mag az ines ▁to ▁review ▁and ▁test ▁in ▁fact ▁had ▁ ▁instead ▁of ▁the ▁ ▁of ▁the ▁rest ▁of ▁road ▁going ▁R S ▁ 3 1 0 0 s , ▁this ▁was ▁achieved ▁with ▁a ▁higher ▁lift ▁cam sh aft . ▁These ▁figures ▁vary ▁somewhat ▁depending ▁on ▁the ▁source . ▁ ▁The ▁Es sex ▁V 6 ▁also ▁formed ▁the ▁base ▁for ▁the ▁ 3 . 4   L ▁Cos worth ▁G AA ▁born ▁in ▁May ▁ 1 9 7 2 ▁and ▁designed ▁by ▁Mike ▁Hall , ▁also ▁responsible ▁for ▁design ing ▁Cos worth ' s ▁famous ▁D F V ▁Engine ▁ ▁the ▁G AA ▁with ▁the ▁benefit ▁of ▁ ▁b ores , ▁DO HC ▁al umin ium ▁al loy ▁heads , ▁Lucas ▁mechanical ▁fuel ▁injection , ▁a ▁dry ▁sum p ▁o iling ▁system ▁and ▁a ▁steel ▁c rank sh aft ▁generated ▁ ▁at ▁ 9 0 0 0   r pm