Originally Posted by bnuk
have you ever seen the bottom side of a head? the water passages in a block gaurd are no smaller than those in the head. so it is not going to resrict the water at all. the open deck configuration was not designed to allow for more water to flow, it was made to be cheaper to cast.
Correct. The flow will be the same, but there will be less coolant around the water jacket. This causes less coolant to be affected by more heat.
Either way, aluminum is stronger than water for holding the factory sleeves together. I'd personally try to find a platform with a cast iron block to make more than 350whp on if you want to run a ton of power on the street. There's no question the rods would have to be upgraded either way for a Honda. 99.9% of street cars don't need a block guard for the morning commute. If it were a un-registered trailer-queen weekend-racer, then it starts becoming a practicality because it won't be used for long; thus, heat will never be an issue.