How you build the carburetor determines to some extent the torque and horsepower curves. And I've witnessed increases in torque well below peak with larger carbs - "in the real world" - and on the dyno. Interestingly, I see more gains "in the real world" than the dyno typically shows. A small difference from one carburetor to another on the dyno can drive and perform like two completely different engines - unless the two carburetors are built the same or substantially the same - with only cfm being the difference.jmarkaudio wrote:A couple of thing to look at with the larger carb, on the dyno look at what effect it has on peak torque, not just HP. If it picks up torque at or even below peak torque it should pick up time as well. A 1250 on my small block matched a 1050 from a few hundred RPM BELOW peak torque and made more torque and HP from there. It was worth .05 in the 1/8 and a .10 in the 1/4 mile. Not always the case, induction and combustion efficiency will play into how large you can go and see a gain.
Example: I saw a 15 lb. torque gain (chassis dyno) on one engine with one carburetor over another, then test drove the car with the added weight of another 200 lb. person in the car to offset the torque gain, the car was much more responsive and clearly spun the tires where the did not with the other carburetor.
I dyno'd a 1 1/2" dia. venturi carb against a 1 3/8" dia. venturi carb. The smaller carb was considered correct for the application, the larger carb too big. The larger carb allowed the engine to take full throttle on the dyno 1100 rpm lower than the smaller carb and made 25 lbs more torque. Both carbs were prepared by carburetor builders and tuned to / for the engine.
Troy Patterson TMPCarbs.net TMP Carbs