Breaking Point On A 440 Block

I am in the same boat as you and today my Indy sourced MP mega block (one of the last 2 in existance as far as I can tell) and 4.25 stroke x 4.500 bore rotating assy showed up at the builder's shop. Try to buy a "Indy, World, Kolene" block - there ain't none to be had new. I could have used a 4.350 bore x 4.375 stroke 440 Source rotating kit I already have with the Chenowith 3/8 girdle I also have (came with a pile of parts I bought off RJ) on a machined stock block, but my research led me to the conclusion that 650 HP is about all a stock 440 block is reliably good for. I am looking for about 800 HP (13-1) and want to have the margin to spray it if I get bored with that power level. Drag engine, race gas only build.

I considered the Indy alum block and a KB alum block, but didn't want to deal with the alum block hassles. Was greatful to find a MP block (Koleno isn't making any, MP isn't either) and had to pay to get it bored to 4.500. We'll see how Indy did me on the parts, hope the machine shop is better at machining than the counter guy who answers the phone is at customer service.

Some folks say alum caps, a good girdle, maybe some fill and you can run higher power with a stock block. All in the tune as they say, but I wanted margin and reliability. Heck, that girdle may find it's way to the MP block if it will fit and I don't have to re-hone the mains.

BTW, I will be using a Indy R2 cam (Comp grind), MRL roller lifters, Indy 440-1 MW 325 CNC heads that have been worked and corrected by a shop (may see a thread on that someday), Harland Sharp 1.6 rockers, and the Indy single plane Dominator manifold. This is basically copying their 800 HP 500" Bracket engine but with more bore (unshroud the valves) and stroke so it will rev and let the cam/heads do their thing. Should rev like a SB.