I'm going to build a 318 stroker for my '73 Duster, and have a few questions about the parts to use. I have a few blocks available, one is the original block from the Duster, but I also have a Magnum 318, and a late '80s factory hydraulic roller block. My plan was to use a 4.00-inch cast crankshaft, and the heads from the Magnum engine. What is holding me back right now is choosing which block to use. All three
engines have never been bored out, so they should all be rebuildable. My buddy says the '73 block is the best, and the thickest, but I'm not sure.
Marty, you are lucky to have three blocks to choose from, and all three will work well at the power level you will be making. As far as actual cylinder wall thickness, the only way to know which block has the most meat is to sonic check them, but this can add up to some expense when considering three blocks. All should be able to take the .030-inch overbore for a fresh engine. The '73 block probably does have a little more meat in it, and it has the advantage of blind head bolt holes, compared to the bolt holes going into the water jacket in the later block. The early decks are definitely stronger.
The late and the Magnum blocks are factory equipped with the hydraulic roller set-up, and if you are wanting to run a hydraulic roller, the later blocks will accept it with all the stock hardware and lifters. This will make the cam installation considerably cheaper than a retrofit hydraulic roller. If I were building the engine, I would choose the '88 block, since it has the hydraulic roller provisions, but does not have all the extra mounting bosses found on the Magnum block.
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