There are alot of high-horsepower v8s without a "girdle" cap. My understanding is lateral bolts into the caps are a geat way to tie caps into the block, but I'm not sure if this is possible on our blocks. While "main girdles" may offer some strength advantage, I think they are designed more to reduce the vibration modes of the block. This enables engine designers to reduce noise. On a alternate thought, I have heard of race teams trying to run long head bolts straight though to the mains to keep the block together.
While I haven't seen the girdle you mention, if you think about the vertical & rotational forces coming from the pistons & rods, I do not see "bridge" supports from other mains providing much vertical support. Now, if your mains are flopping around like flexing potato-chips at 1950Hz... tying the mains together with a girdle may increase this "potato-chip" mode to say... 2800Hz where for instance it might not interact with a crank mode at 1953Hz. (frequencies in this example have been changed to protect the innocent :^)
Last edited by bjones18; 01-09-2011 at 05:28 PM.