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I wouldn't plan a 4.5 stroke in a 440 block for anything beyond about 600 hp, and then only if I had a very light rotating assembly and / or a center weighted crank to help relieve stress on the bottom end combined with small port heads....

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At that point, why bother with the long stroke if you're not going after a big HP number? Get a Megablock or other aftermarket block, let it eat, and sleep soundly.

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The reasons are budget, what's on hand and the torque range desired.

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Well, of course, Greg. But, having a limited budget doesn't trump common sense, and most of all, safety. Like Monte said, you'll never know when the bomb will go off, and if it lets go at the top end, the resulting damage will be a lot more than what an aftermarket block costs.

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Dave, I don't understand the "common sense" comment? I believe we are on the same page. That is, a stock block has its limits. You can only push it so far, then you risk breaking it, and the risk goes up with the stress you put on it like anything else. If a guys budget doesn't have the funds for an aftermarket block, then the build better take the risks into consideration, or the builder better understand the risks.
Increasing the stroke from 3.75 to 4.5 raises the stress on the parts by 44.5 percent. Raising the rpm from 5500 to 6000 multiplies that 44.5 percent by another 20 percent, for a total of 170 percent of the original stress of the 3.75 stroke. If your parts are 40 percent lighter, the whole deal falls back to a two percent increase in stress when you compare a stock weight 3.75 stroke motor to a 4.5 stroke light weight assembly with the rpm limits I talked about. So I see it as apples to apples due to reduced rpm and light parts IF you run it in the right rpm range, and aren't hurting it with a bad tune or nitrous. Most motors can be pushed about 50 percent higher than they were originally designed for. On an old 440 block I wouldn't go that high.

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