I remember what our local, quite sharp dealership parts guy told us in the mid-70's, that if you bought a 428 service block then, you would get a bored out 391 block, as they were using one service casting based on the 428, but only (normally) bored to 4.05- which would of course be a cost savings over casting different blocks for service use when not necessary. Actually makes perfect fiscal sense, and would explain some 360s and 390s with "thick" walls
bingo, dead on the money. Every single one I have seen so far is a mid seventies block. My guess is, theres a lot more out there to be found, I would be willing to bet there were probably at least 500 or so cast its a simple question of economy of scale. Ford didn't do 5 or 6 blocks at a time for bread and butter stuff, they did hundreds at a time. By casting them all on 428 cores, they didn't need to cast, and warehouse two runs of blocks, one for 360/390s, and one for 428s, they could cover both replacements with the same block, and machine them to the bore size they needed.
Of course, when you think about how many MILLIONS of 390 blocks were cast over the years, they are going to constitute probably less than 1% of the total number of 390s out there, (which is right in line with Barrys quoted numbers) and probably quite a few thick (and thin) blocks are Toyota corollas by now, so you are going to have to look at a HELL of a lot of 390s to find one. If you are looking for one, once you realize they are all late blocks with the vertical ribs, you can eliminate a lot of them without even popping a freeze plug. Theres still a damn site more thick 390 service blocks out there than there are OEM 427 cammers, and if I went on an internet forum and said those "didn't exist" the same guys that are saying "all 390s are thinwall" would go spastic.
But blabbing about cammers is "cool", talking about thickwall 390s clearly is not.
FWIW, my block came to me indirectly via another one of those "old-school" Ford guys like Gene is talking about, he was pretty well known locally, there is at least one member silently lurking this thread who knows
exactly who I'm talking about, he also had two shotgun mustangs, one pretty much stock, the other with a raised port, dual dominator Pro-Stock motor in it, the second one was pretty notorious among local street racers in the early seventies. Lots of those guys knew about these blocks back in the seventies when they were new, hell I knew about them, and I didn't have any kind of inside track, I was a punk kid at that time.
Its a fair bet that a fair percentage of that 500 or so have been hoarded by the few guys that knew what they were, and there are probably a few out there like mine, that have been sitting in a dry basement for 20-30 years. A lot of those guys are older than me, (and I aint exactly young) and are probably closing in on the time when they are going to stop hoarding this stuff. But hell, they "don't exist" so you guys here don't need to worry about that.
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