The stock Bronco Throttle Body is 51mm.
The BBK #3501 is a 56mm Throttle Body.
The BBK #3503 is a 61mm Throttle Body is for high RPM applications and 460 engines. It also requires port matching to the intake manifold and a tune correction prior to installation.
Throttle Body Sizing and Horsepower Level
Dual 51mm = single 72mm = 470 HP
Dual 56mm = single 79mm = 570 HP
Dual 61mm = single 86mm = 670 HP
I may change to a BBK 61mm when I change my tune, as it is tunable and only affects performance at or above 3500 rpm, but the BBK 56mm is fine for now. Regardless of which Throttle Body I use, my low rpm torque will still be the same. And I am not sure why there is such a buzz about a single 90mm Lightning Throttle Body when the focus should be on low RPM torque, not high RPM Horsepower. This is a heavy truck, not a lightweight Mustang.
Heck, a MAF Sensor should not be too small becoming a restriction and should not too large which tends to loose resolution and accuracy. I am curently running a 75mm Pro-M Mass Air Meter that was factory calibrated to 19 lb injectors. The 42 lb/hr calibration was correctly done in my tune.
Mass Air Meter Sizing and Horsepower Level
55mm = 275 HP (Stock 88-93 Mustang)
70mm = 350 HP (Stock 94-95 Mustang)
75mm = 550 HP (75mm Pro-M Bullet)
80mm = 450 HP (Stock Ford)
85mm = 650 HP (85mm Pro-M Flanged)
95mm = 750 HP (95mm Pro-M Flanged)
80mm = 800 HP (Pro-M 80 mm )
92mm = 1500 HP (Pro-M 92mm)
With a 351W, look at an better flowing Intake and mandrel bent Y-pipe and 3" exhaust first. With a 302W, go for the Y-pipe and exhaust. That is after you have done a quality tune-up and ensured that your PCM was happy...
opc1:
