In our Aug. ’09 issue, we did a story on a 408ci small-block built with a 4.00-inch stroke crank where the engine builder used Hard Blok in the water jackets. This is a material poured into the bottom of the water jacket originally designed to stabilize thin cylinder walls and limit bore distortion. In our story, the Hard Blok is used to prevent water leaks when trimming the bottom of the block to clear the longer stroke crank. One point that a race engine builder told us is that the material is porous and is not designed to seal leaks, which appears to be why this material was chosen in the first place. But there’s also the discussion about whether this Hard Blok will affect engine cooling. If the level of Hard Blok is minimized to roughly the bottom quarter of the water jackets, the biggest effect on cooling will be oil temperature. For a drag race engine that sees only competition use, this could actually be a benefit because oil temperature comes up quicker and is higher in an engine that normally never achieves full operating temperature. With a street engine, it’s important that oil temperatures exceed 212 degrees F to ensure that the inevitable water that condenses in the crankcase during cold engine operation has a chance to turn into steam and be evacuated out of the crankcase. However, oil temperatures that exceed 250 degrees F when using conventional (not synthetic) oil can contribute to engine damage resulting from reduced lubricity. Synthetic oils are far more stable at elevated engine oil temperatures of 250 degrees F and above. If the engine experiences oil temperature exceeding 250 degrees F for street use, it would be a good idea to add some kind of oil cooler even when using synthetic oil to help the oil do its job. Do not assume that just because the water temperature is below 200 degrees F that the oil temp is also low. Oil temperature often exceeds coolant temperature by a wide margin.