Combine lemon juice, pineapple syrup, pisco and water in a jar or pitcher. Pineapple juice may be added more if a sweeter punch is desired.
To serve, fill a glass with ice cubes and pour punch.
Cut pineapple into chunks and place in a large size saucepan with water and sugar. Bring to a boil for 10 minutes. Blend pineapple chunks, return to the saucepan and bring to a boil again for 20 minutes more.
Strain twice to eliminate any solids.
Keep this syrup refrigerated. It can be kept refrigerated for several days.