Ported heads,bigger carb for more fuel economy

[BigBro74]

A 600 with annulars would have needed minimal t-slot operation as the mains would be active fairly soon in the throttle opening. Dropping the float level might help a little as well to delay the mains.

Mark, you are probably getting to it with these points. this car had a 5 speed, and in overdrive going down the highway there was VERY minimal throttle opening, even at 70 Mph. it has been many years ago, so I don't remember all the specifics now, but do you think the 850 carb was running on t-slot for cruise? never thought of this back then for sure..

[Lasher...]

Gearing and load can have a big impact on fuel economy.....As a real world example a well known west coast Super Gas racer and his buddies were traveling back to Calif from Indy..... 454 crew cab TH 400 and 3.73s pulling trailer and race car.... unknown total weight.....one of the guys noticed some puffs of black some coming from his exhaust ....and he was complaining about horrible gas mileage with his QJet....So after spending the night he went across the street and some auto parts store and bot a Spread Bore to Std flange adapter....took the 850DP off the race car along with the air cleaner and swapped them onto his truck and headed back to the west coast....this 850 got 3 MPG better than his QJET..... it turns out that with the heavy load and gearing with the QJet he was actually into the secondaries cruzing down the highway....but with the much larger primaries on the 850 he stayed in the primaries and thus got better fuel economy.