Trying every size of carburetor on our LS to see how much horsepower they could get | Driveway Finds

TL;DR

A budget LS-swapped 1966 Mercedes was dyno-tested with five carburetors from 1150 CFM down to 40 CFM Harbor Freight units to measure horsepower impact.

Key Points

• 1.The 1150 CFM Holley Dominator made 347 hp after jetting correction. Initially ran lean at 247 hp with stock 80 jets; jumping to 99 jets added 100 horsepower, revealing the engine's true output from a mystery cam LS2.
• 2.The 650 CFM Holley double pumper made virtually the same 344 hp as the Dominator. Despite being nearly half the CFM, the small 5.3L LS2 couldn't fully exploit the Dominator's extra airflow capacity, making both carbs functionally equal.
• 3.Dropping to the 300 CFM Rochester two-barrel caused a significant 100 hp loss, yielding 246 hp. Jets were drilled from 60k to 76k to richen the mixture; below wide-open throttle the smaller carb actually felt faster due to higher air velocity.
• 4.The 190 CFM monojet one-barrel made 183 hp, roughly 100 hp less per barrel removed. Designed for 1960s Chevy straight-sixes, the team was shocked it ran at all on a high-powered LS, with the engine audibly starving for air at the top of the rev range.
• 5.Three 40 CFM Harbor Freight Predator carburetors linked via a 'Predator Ram' made 95–110 hp. Initially producing only 36 hp stock, drilling jets from 29k to 75k and tuning idle mixture pushed output past the 100 hp target, with the intake temperature dropping to 120°F from evaporative cooling.
• 6.The engine is a budget 5.3L LS2 with a mystery cam from the Turlock Swap Meet, low compression, and 706 heads. Pulled from a Pick-and-Pull junkyard, it has survived burnout competitions, a destroyed rear axle at LSFest, and 12 cumulative minutes on the rev limiter.
• 7.The car was driven 20 miles home on three Harbor Freight carburetors after completing a burnout. Despite the hood needing removal for clearance, the car performed well enough that the camera car struggled to keep up, validating the absurd experiment.