Zamac 2 for under $2 a pound.

The composition of Zamac 2 by percent is

Aluminum  3.5-4.3
Copper 2.5-3.0
Magnesium  0.02-0.05

Iron (max)  0.1
Lead (max)  0.005
Cadmium (max)  0.004
Tin (max)  0.003
Zinc  Bal. 

Seems the Magnesium is optional.
Pennies are 2.5% copper and 96.5% zinc.
A penny weights 2.500g.

Lets stick to metric but note that a lb is 453.592g or 181.4368 pennies.
Lets round up to 182 pennies for each pound we are alloying.

How large would a crucible need to be to hold 5 lbs of zamac 2?

In Imperial or US customary measurement system, the density is equal to 426.383 pound per cubic foot [lb/ft³]... .

Lets do 1 lb first.

so 426.383:1 as 1:x

or 1/426.383 = 0.002345309 cubic feet or 4.0527 cubic inches

4x4=16 or 16 cubic inches for 4 lbs.   Would be nice to use a steel pipe if it did not contaminate the metal.  Maybe if its seasoned first.

Casting Temperature 

Zamac 7 Casting temperature

395—425 °C

743—797 °F

Melting temperature of Zamac 2 is about 6 degrees F higher so maybe 805F for casting.  Guess here.

Procedure 

Buy and clean 4 lbs of pennies.  Thats 4x182 or $7.28
In theory they should weigh 728 x 2.500g or 1820.000g
We know 975% of the pennies are Zinc.
So  .975 x 1820 = 1774.500g and 45.5g copper.

How much is 1% of our total.  We know 1774.500g of  Zinc comprises 97.5% of the penny but only 93% of the Zamac 2. 
1774.500g/97  =  19.081g is 1% so 100% is 1908.100 grams.

Assuming the 7% is 4% aluminum and 3% copper we need
aluminum  4x19.081g = 76.324g

The pure aluminum will come from ingots from aluminum cans.

total copper 3x19.081g = 57.243g

Note that we must include the copper from the pennies in this.
Assume the missing weight in the pennies is due to loss of copper.
So we will add that amount of copper, solid house wiring, to make up the difference. 

Found this
http://gizmology.net/stovetop.htm