Internal combustion engine with air-fuel mixture heating

In an internal combustion engine, the combination comprising:

• (a) a cylinder block having a cylinder and reciprocable piston disposed therein, said cylinder having a wall with an intake port and an exhaust port therein,
• (b) an exhaust chest disposed in said cylinder block for receipt and transfer of exhaust gases from said exhaust port,
• (c) a cover for said exhaust chest and with said cover disposed in facing relationship with said exhaust port,
• (d) a carburetor connected to supply a primary air-fuel mixture to said intake port of said cylinder, said carburetor having a primary fuel passage and a throttle valve adjustable between closed and open positions,
• (e) and means connected between said carburetor and said intake port of said cylinder for supplying a supplemental heated air-fuel mixture to said cylinder at idle and low engine speeds,
• (f) said supplemental air-fuel mixture supplying means including passage means disposed in facing relationship with said exhaust port of said cylinder wall for conducting said supplemental mixture therethrough so that exhaust emanating from said exhaust port into said exhaust chest heats said supplemental mixture,
• (g) said passage means is disposed in said cover having one end connected to said carburetor and its other end connected to said intake port of said cylinder, and
• (h) the connection of said passage means to said carburetor includes a secondary fuel passage in said carburetor, means connecting said secondary fuel passage to said passage means in said cover, and external air inlet means disposed in said connecting means to provide said supplemental air-fuel mixture, said external air inlet means includes a restrictive air metering orifice of smaller cross section than said connecting means.