Well...this is the reason I'm asking these questions. I have this 390 block that I've been tinkering with...and I thought it was a buy until last night. It's a 67 C7ME-A casting....and high nickel.
I had the thing magnafluxed last night...no cracks...I also had the cylinders sonic tested. Most of the cylinders were very beefy...(it is a stock 4.050" bore). The majority of the cylinder walls were in the .160"-.180" range. However, there was an area in the #1 cylinder about the size of a quarter where the thickness was .134". It was in what I call the bottom of the cylinder...if you're looking directly down at the passenger side cylinder deck, it would be at the bottom...towards the header or
oil pan.
I really had my heart set on boring this thing .080" over and making a 427 out of it. However, if my buddy was right (he is a welding inspector with a $5k piece of equipment), taking .040" out of that side of the cylinder would make it .096". Ouch. I called the guys at Gessford, and they said for a street engine, they wouldn't wanna see anything at all less than .100" on a cylinder.
So basically I'm standing at the crossroads. I wish we would have skipped that cylinder...it was the last one we did.
What really sucks is the rest of the cylinder was anywhere from .154" to .179" on the other sides. It's just that small little section that worries me. I hate to scrap the block...I've got some money in it already from having it cleaned, etc...I could always just bore it .040" or .060" (machinist said it needs .030" to .040" to clean it up due to a few pits in the #1 cylinder), and end up with 418ci or 422ci with a 3.98" stroke. I really hate to do that though.
What would you guys do? I need some help. Basically I have two options...One is to just bore it what it needs to be cleaned up and end up shy of 427ci....or go ahead and bore it .080" and just hope that little quarter sized part doesn't blow out....