If my impala is a SS. Did the 283 it came out with have any more high performance than one that isn't a SS?
Doe the air cleaner say what HP your engine is rated at? This might help -- http://www.oldride.com/library/1964_chevrolet_impala.html
I believe the 283 was rated at 195 hp. For more performance you had to get a 409 or a 327.
63 was the last year for the 409 in the cars and 64 was the final year of the 409 in heavy duty trucks, and also u may want to have check the numbers on the car itself to see if it is actually an as and not an as clone
From what I have found there were over 8,600 64 Impalas sold with 409's.
Looking for a Used Chevrolet in your area?
CarGurus has 725,876 nationwide Chevrolet listings starting at $695.