Old toilet on a 3" waste line

[MajMetro]

Can an old "large tank" (can't remember the gallonage) toilet flush properly into a 3" closet el and trunk line? I'm remodeling my basement and trying to keep my main floor bath untouched (if local code enforcers allow). My existing main line is 4" cast, but due to my new basement layout and depth of the line below my slab, I would like to run smaller 3" ABS.

Thanks

[hj]

It was being used long before the low flush toilets were designed. In some cases it will work better than 4".

[MajMetro]

Thanks hj. Being a jack-of-all-trades and master-of-none, it's always comforting to check with a professional.