Unusual 390 block
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Junior User
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Unusual 390 block
I believe I found a marine 390 block living in my white 66 galaxie.
I pulled this engine out last night, intending to use it as a turn in
core for my truck motor. There is no part number on the side of the
block, but it does have the usual 352 cast on the front.
the date code under the oil filter 9D23 and there is an "M" cast
under the date code.
Now here's the unusual part, the back of the block looks just like a
427 block, it has a 66-427 cast into it, the two bosses for the oil
pressure relief valve. and the extra ridges like a 66 or later 427
block that has the oil drainback for the SOHC.
But from the side it looks just like a standard 390. pressed in freeze plugs, no crossbolts. I the bore on the cylinders is 4.080, so it's is a 390, just bored 30 over
So the question I have is...
Does this block have thick cylinder walls cast like a 427? Even though it's only bored to a 390 spec? Or could I at least bore it to a 428 bore?
Thanks all,
Dane V
71 F250 hiboy
I pulled this engine out last night, intending to use it as a turn in
core for my truck motor. There is no part number on the side of the
block, but it does have the usual 352 cast on the front.
the date code under the oil filter 9D23 and there is an "M" cast
under the date code.
Now here's the unusual part, the back of the block looks just like a
427 block, it has a 66-427 cast into it, the two bosses for the oil
pressure relief valve. and the extra ridges like a 66 or later 427
block that has the oil drainback for the SOHC.
But from the side it looks just like a standard 390. pressed in freeze plugs, no crossbolts. I the bore on the cylinders is 4.080, so it's is a 390, just bored 30 over
So the question I have is...
Does this block have thick cylinder walls cast like a 427? Even though it's only bored to a 390 spec? Or could I at least bore it to a 428 bore?
Thanks all,
Dane V
71 F250 hiboy
Cargo Master
Joined: Aug 2000
Posts: 2,931
Likes: 12
From: SW Michigan
Unusual 390 block
Not as unusual as you might think. Apparently when Ford was casting these blocks, the production line was in a hurry. If the back plate from a 427 mold was handy and they needed to keep the line going......then that is what they used. The best way to guess if you have thin, average, or heavy cylinders is to see how big of a space you have between the cylinders. Our friend 'Shoe' from 741982 uses the smooth end of a drill bit to check. Measure yours and we will try and tell you how big can you go. DF
Freshman User
Joined: Sep 2002
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Unusual 390 block
hello everybody i am new here and so it seems i have run into a bit of a problem i own a 1972 ford f250 4*4 390 bored 60 over and a bunch of other high performance parts never the less i got a little to heavy on the nitrous and blew my oiler rings so i thought to hell with it i will start again so a friend of mine told me to go see a buddy of his that owns a scrap yard so i phoned the guy he tells me yeah i got a 1968 gt390 so i was on it when i got there it was sitting there with a price tag of 500$ so i looked a little closer and yes it had the gt390 heads with a dual bolt pattern i thought perfect i got it home and started to clean it up took the short block to the local machine shop they called me the next day and told me they ran the # on the crank it came back 427 so i went down there to see if i could get # off the block i looked everywhere no # anywhere it looks like a 390 from the side but it looks like a 427 from the rear it has the 352 marking someone told me it might be a marine block if you can help in any way it would be muchly appreciated
Senior User
Joined: Oct 2001
Posts: 479
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From: Miami U.S.A.
Unusual 390 block
FORD COWBOY If you are wondering if it is a 427. Why not measure the bores?? The machine shop has to be somewhat into it already if they told you the crank was a 427 unit. Now that I think about it you were probably just adding info my BAD.
Scotty
Scotty
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Unusual 390 block
If it's not as unusual as I thought well then good,
I will take your suggestion and get the drill index out, knock out the freeze plugs and see what fits between the walls.
Thanks for the help
I''ll post results back in a day or two
Dane V
I will take your suggestion and get the drill index out, knock out the freeze plugs and see what fits between the walls.
Thanks for the help
I''ll post results back in a day or two
Dane V
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Joined: May 2002
Posts: 112
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From: aubrey usa
Unusual 390 block
That is a .020 over bore 390 block. I think a standard 427 bore is around 4.23. The 427 crank number was common in 390 engines since they are the same stroke. If it is a true 427 crank it will be steel instead of cast. Hope this helps
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Unusual 390 block
i sure as hell hope so.what are the odds of it being a 352 block stroked 70 over or a 410? is there any special markings on the 410 that would stand out.and yes it is a steel crank and how can i tell if it is a regular 390 or gt390 or is that all in the heads?
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From: Miami U.S.A.
Unusual 390 block
Cowboy Check the block for casting #'s. Under the oil fliter mount there is a series of #'s. Something like C8AE-A. OR could be any # but that is what it would look like. That will determine what block it origanlly was cast as, well maybe.
There are a few Casting #'s that could be trced to nearly anything from a 352-428 and everything in between. Hope this helps
Scotty
There are a few Casting #'s that could be trced to nearly anything from a 352-428 and everything in between. Hope this helps
Scotty
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