It's made to be a poor-man's solution to sleeving a motor. AEBS, Benson, and a few other companies make full sleeves that replace the stock sleeves. They include a closed-deck design (to a degree) that anchors the tops of the cylinders by closing off the space between the tops of the cylinders and the block where the water jackets are. This eliminates potential dangers that a motor making a good deal of HP might face. The block guard simply is the top portion of these sleeves, but is not in any way as good as a replacement sleeve with the built-in block guard. Many people actually ruin engines by attempting to install them. If you're serious about making power and think you need a block guard, get new sleeves installed. You will be much happier with the result.