Hi there! I'm going to be having a 400ci Smallblock built for me in mid december to match a pair of Dart Iron Eagle cylinder heads I picked up just recently. I was shooting the breeze with a friend at work (and an experianced mechanic at that), and he advised me to fill the water jackets, noting that he had learned to do this the hard way with 400s. He cited that the cylinder heads are the component that require the most cooling, and that filling the water jackets with a block filler (HardBlok, etc) would reinforce the block.

I wanted some input from some of the experianced folks here at CHR. Do you agree with this advice? I doubt the motor will be making more than around 380 crank horsepower.

Does this technique significantly increase block strength? Will I notice a detriment in my cooling efficiency?

Thanks in advance, always appreciate a little help with these things.

-Rob