a method and apparatus for assembling heat exchanger elements includes a pallet comprising a frame and a plurality of blocks slidably aligned on each side of the frame with opposed pairs of blocks slotted to receive pairs of plates dropped into the pallet . lead screws driven by servomotors and engaging the blocks position the blocks at the loading station and control the block spacing to allow plate insertion or to allow insertion of fin elements between the plates . to quickly move the pallet into the station auxiliary lead screws connected to the main screws engage the blocks of the pallet outside the loading station to assert positive controlled advancement force on the pallet .