Quote Originally Posted by FFR428 View Post
I agree. Most casting numbers are generic and used on many different bore blocks. The C5AE-6015-A is one of them as you see. I have seen some of them go to 4.13" std 406-428 bore but 4.23" would not be likely. And having the cross bolt bosses is a nice option to crossbolt w/factory or aftermarket caps. Some of the C5AE-A blocks were also solid lifter blocks used in the 390 PI engines. Some 352's had that casting number too. Dave Shoe's drill bit test will tell you aprox what you have for cyl wall cores. But as Shoprat said a sonic map is best for exact results. Nice find on that virgin. Not many of those around anymore.
I was suprized to find it was a virgin block too. Very little rust in the cores and no sludge in the engine. Only problem I found was the #1 and 5 rod bearings were 10 miles away from spinning. Other than that the crank was perfect. But it should clean up at 0.010 under.

I did the drill bit test and if one of those blocks can be bored to 427 spect it's the virgin. Slightly bigger gap than .180" between the cylinders. I'm gonna get is sonic checked and I have my fingers crossed. The other may only be able to go 0.060 over 390 specs. Lots of rust in the cores of that one. When I got it all 6 core plugs were rusted through. That one is a good candidate for a muratic acid bath to get rid of the rust. That block is already 0.030 over and may be junk but at least the crank and rods were good.