Thread: '63 390 block with unmachined crossbolt bosses

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I rebuilt a 390 pulled from a '64 T-bird for my '69 Torino and noticed it had the thicker webbing and cast but unmachined or drilled bosses for side bolt mains. C3AE-D block, cast C3AE-G crank with the 1/8" groove like is found in the early 427's, C3AE-F rods with larger 13/32 bolts as found in early 427's, 390 4.05" bore, normal C4AE-G heads, and drilled oil passages for hydraulic lifters. How common is it to find the high strength webbing and cross bolt bosses in the early non-406/427, 390 bore FE blocks? The books I have show the block casting number to be a 406 so maybe if the cylinder wall thickness was off they just bored it to 4.05" instead of the 4.13" of the 406? Then again my books are not perfect and I find lots of different opinions on casting numbers so just curious if anyone else has used the early blocks with the same findings.

That's pretty common to find crossbolt bosses in the 63-64 blocks. I've had C3AE-D 406 blocks so it's very possible yours can be bored out. You need to inspect the cyl wall cores to see. You need to knock out the blocks freeze plugs to access the wall core area. If a 13/64" drill bit shank is a snug fit good chance the block has 406 wall cores. Something common to the 406 blocks are "HP" cast in the block on the back, side and inside the block. You'll need to sonic map the block even if you do find thicker wall cores. It might be coreshifted and was only able to accept a 4.05 bore. But the drill bit test will confirm what cyl wall cores the block was cast with. That's pretty interesting as I've never seen or heard of a C3-D block being drilled for hyd lifters and having a 4.05" bore. So please keep me posted what you find. Every C3-D block I've come across has been a solid lifter 406 block with 4.13 bores with the HP markings cast in. I've had 5 of those D blocks and several other 406's as well. Can you send me some pics? This is a first that I know of.


G.