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Thanks for the advice regarding the 428 or 390. But I want to keep stock looking appearance on the 390, the car has a 428 crank already, what else needs to be done to increase the displacement to 428 or more. Thanks
 

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a different block
 

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The 428 block has a .080" larger bore. I've heard some of the early 390 blocks can be bored that much but I don't know that for certain. Someone else will probably be able to confirm or dispute this but if they don't I'd have the block sonic checked to see if the cylinder walls are thick enough to be bored that much. The down side is even if you can bore it out to 428 size you're left with a block that can't be bored again, so once it's ready for a rebuild it will be time for a new block too. A 428 crank with a stock 390 bore is 410 c.i. (a Mercury only engine but still factory made), and if you bore the standard .030" over for a rebuild that would bring you up to 417. 11 more cubes may not be worth the extra cost of boring it that big (the machinist will probably have to make 2 or 3 passes to cut .08" from the cylinder walls). If it were me I'd put the money towards improving the heads. There's more power to be had there than by adding 11 more cubic inches.
 
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