im running a 1641 tp electronic ignition 009 dizzy 4 into 1 header with twin kadron 40,s got the revs set at 4000 rpm i normaly change up well before that but if i push it a bit i know im still safe when the change light comes on. i get 70 mph at 3800 rpm in 4th but i wouldnt hold it there and cruise her on 3200 rpm to 3500 rpm that gives me about 55 to 62\63 ish once i start pushing over 3500 rpm im using a fair bit more fuel for virtullay no gain but as daft as it sounds and i know someone will probaly say .coblers. but im getting better fuel economy out of the twin 40,s than i ever got out of the single solex 34.. :?