What rods and pistons would I use with a 425 crank? and whats the difference between the 425 crank and the 455? If I did stroke the block I have, I'd want at least 400 cubes. what crank would get me closer to that ball park? Also, what to do about the gap left by the injector pump on the DX block? On the other hand I could pick a Cadi motor up for $300 bucks, then all the new parts, but I don't know how to get any more performance out of a 500. And then all the extra weight...
A caddy big block is relatively light for how many cubic inches they are. Lighter than a big block Olds for sure, honestly probably lighter than an older 350 diesel. As I recall an all stock 500 with iron heads, intake, and exhaust manifold weighs about 75 lbs more than an all iron 350 chevy. Shorty headers, aluminum intake, and if you have the money heads, and it weighs about the same as an all iron SBC.
They have a lot of potential, the three things that hold it back in stock form are the oil system, rockers, and connecting rods. Aftermarket rockers are more expensive than typical engines because only a few specialist places make them, everyone pretty much agrees they MUST be upgraded for any kind of performance work, the stock rocker setup is fragile.
Big block Chrysler 440 rods can be modified to work with the Caddy block and crank which opens up pretty big number of options for rods. Or alternatively you can get nice forged i beam or H beam rods for Cadillac now, they're a bit more expensive than Chevy rods but in line with other BOP and Caddy performance parts, but cheaper in the long run than using Mopar rods because there shouldn't be any special machine work needed. Cool thing about using Chrysler rods is since they're smaller big end diameter, the crank needs to be turned down to use them, but that means you can have the shop offset grind the journals and make your 500 caddy a stroker, think it makes for like a 535 but I can't remember the exact details.
That said, if it were me, and this is just my opinion... If you are not going to run a Chevy engine, and you want to keep it Olds, I'd find a 400, 425, or 455 and rebuild it and plop it in there. Should fit perfectly where the 350 diesel was, and won't be as expensive a headache as converting the 350 diesel into a gas powered 400+ ci stroker. It'll still be an expensive headache but not nearly as bad.
400 or 425 would be my first choice.
