Becoz it's.....it does about 15mpg
Even without the cam, with that size of engine and triple SUs it'll be a thristy beggar. My Dolly Sprint was thirsty as heck, without the extra 1000 cc of the MGC.Got tripple SU carbs and a full race cam
Won't you need to change the dizzy or was the vacuum advance just missing?
Best of luck with it all.