Having designed a couple of engine carts, I would suggest that 3" minimum diameter solid body wheels on swivel frames would be the smallest wheels you should use. Napa has them and so does Home Depot and several other suppliers locally. The wheels on the cart in the picture look to be medical grade, meaning a small rubber "tire" mounted to some kind of "rim". And yes they will fail, particularly if you are trying to wiggle the cart to get it into a tight space.
One of the best carts I ever built was made by using a furniture mover base and adding side rails made from sections of 2 x 8. cut for length with one cut shorter than the other to provide room for the filter to stay mounted. The engine slipped in between the vertical boards and the pan flange sat on the upper edge. Up near the front of the pan where it gets shallow there was room to add a side to side brace to stiffen the vertical boards and keep them from spreading. The wheels on the mover were way sturdy enough to handle a small block and likely could have dealt with a big block with a little more bracing. As a matter of fact, my 400 block is now resident on that dolly.
Nick
One of the best carts I ever built was made by using a furniture mover base and adding side rails made from sections of 2 x 8. cut for length with one cut shorter than the other to provide room for the filter to stay mounted. The engine slipped in between the vertical boards and the pan flange sat on the upper edge. Up near the front of the pan where it gets shallow there was room to add a side to side brace to stiffen the vertical boards and keep them from spreading. The wheels on the mover were way sturdy enough to handle a small block and likely could have dealt with a big block with a little more bracing. As a matter of fact, my 400 block is now resident on that dolly.
Nick
