ok so i know that the 401 and the 425 have the same stroke but different bores, does that mean a 401 can be bored out to a 425 or was there something completely differnt in the blocks in 66?
General consensus is that the blocks are different. Only way to know for sure how much a 401 or 425 can be safely bored is to have the cylinder thickness measured with a sonic tester.
thanks walt, i was just curious. im hoping i dont have to touch the bottem end but i have a feeling the motor is going to be coming apart.
http://www.v8buick.com/showthread.php?t=10623&highlight=401+maximum+bore Plus I think Tom T pointed out that the Buick factory literature says the max bore permited on a 401 is 10/1000". Ask Tom to make sure that my recollection is correct.
The recommended overbore on a 425 is .010". But, I would sonic test ANY 401/425 BEFORE boring. Even on a stock rebuild that will need an overbore I recommend some epoxy block filler.
