@ADCX Rob answered your direct questions, but I would also suggest you look at servicing your smoke units.
Service documents are kindly hosted by Olsen's here: http://www.olsenstoy.com/searchcd31.htm?itm=629
Of special interest is adding the 2026-44 spring to all piston based smoke units. The service documents notes that it decreases noise, but I also find that it helps prevent the piston return so that it is able to travel the entire cylinder boosting smoke disbursement. Additionally, these smoke unit shave been around for a while and may be gummed up with gook. A good cleaning couldn't hurt as well as replacing the batting (referred to as smoke unit lining).
Also, some of the initial smoke unit heating elements had 9 turns of nichrome wire. Lionel revised this to 8 turns. You can either adapt or replace yours.
Some parts suppliers offer "liquid conversion kits" but I avoid those as unlike the original style, they can burn out easily if not constantly soaked with smoke fluid. The original units can run pellets or liquid as is just fine, or be run empty with no similar concern.
