I use an 850 DP on my 440/493 and I drive the car 90% of the time. I have never had a problem of washing the cylinders down. I have it set where it drives nice and works good at the track. Heck my eng even wants more carb but this 850 DP works great. If you are washing cylinder walls with an 850 DP you have something wrong and dont have the carb set up right or its just to much carb for the combo. Mine never fouls plugs with all the street driving I do. Last time at the track I raced with the same plugs that had been in my 63 for over a year. Ron