Hydraulic Vise using car jack

My old vice isn't work as good as it should be so I decided to make new one.
I took materials from the scrapyard. The jack has capacity about 5 tonnes.
I suppose that it hasn't so much capacity but it should be sufficient for my needs.
The whole vise weighs about 40 kg/90lbs.
If you have a question to me about this vice, just let me know in the comment section.