Hi. My name is Chuck and I'm new to the forum. I need to find another block for my '64 Riv. Are all of the 401/425 blocks interchangeable between years and casting numbers? Thanks
You can put a 401 in place of a 425 as they are externally the same, but the 401 can not usually be made into a 425. Some 401 engines have been bored to the 425 size, but this is the exception rather then the rule (sonic testing is required as a prerequisite). You would need a 64-66 401 or 425 to bolt directly in place of yours. Cheryl
