Could you use an old battery?

I have a bunch of old aircraft open cap cell vented manifold battery's at work. I was thinking of emptying the acid out and replacing it with water and baking soda, connect to directly the the cars battery then run the hose from the manifold outlet to the intake of the engine, teoretically it should work. Anyone have any thoughts on this?

it very good ide but it will never work becouse battery is using led panels so you will used it but he whant last to long soon is stard the heding problem it will meld. you can give a tray BUT MAKE SHOUR DO IT IN OUT SIDE OF YOU HOUSE OR WORK !! LED IS VERY DANGERAS WHEN YOU MIX SODA

I like the idea of using the casing but not the insides. I have been looking at an old scooter battery with the idea of using the casing for a small HHO cell. An old battery has several problems as pointed out by Kemkarakurt, add to that the problem of warped plates and putting power through them and the whole thing becomes dangerous!