Rotary carbs and slide carbs have identical top-end power characteristics...it doesn't really matter once the throttle servo tugs them WFO. At partial throttle settings the slide carb provides superior airflow due to the simple fact that the air does not have to follow a convoluted path through a half open hole that's machined in a small cylinder of steel. The slide carburetor, even partially open, has no such obstruction and the intake charge has more of a straight shot. It's about a 50/50 mix of slide and rotary carbs in the top ranks of 1/10 scale stadium truck racers, although they have been known to swap between carb types depending on track conditions. Almost every 1/8 scale off-road car and monster truck has the throttle linkage configured for a slide carb.
It's ironic that a typical race engine more often than not will actually outlive a beginner 'sport' engine, due to the simple fact that a savvy racer will take care of his equipment, retune as conditions change and perform regular maintenance, compared to the newbie or hobbyist who is more likely to make user errors during break-in, or impatiently lean their sport engines out trying to impress friends while bashing.
ORIGINAL: nascardad24
slide carbs are for buggies and monster trucks. I ordered a OS with a slide and the fella at the hobby shop said it wouldnt work, that I needed the rotary type.
Rotary carbs offer a larger response in the middle of the power
band. This works well for off-road applications when throttle
response must be varied.
Slide Valve carbs provide greater response at the beginning and end
of the power band. This works well for on-road and racing
applications for fast take-offs and high speed.
Many high-performance engines have short lives, as racers constantly
strive to "lean them out" for greater performance. Unfortunately,
it also makes engines run hotter, which reduces their lives.