390 safe bore?
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Postmaster
Joined: Dec 2003
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From: Honkytonkville
390 safe bore?
Can a 390 (105 cast on front) be safely bored to a 4.23 bore.......Supposedly 427s and 390s have the same bore spacing so this SHOULD be doable...on paper. Any experienced folks know this one?
Postmaster
Joined: Jul 2003
Posts: 2,711
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From: Pittsburgh
Same bore spacing, but the 427 is actually a totally different casting from all other FE blocks. There is no way that you're going to get any 390 to bore out .180". Now, if you were to take the block to a really good machine shop they'd be able to sonic check the block and let you know the max safe overbore.
If you're REALLY willing to throw some money at it, ask them if they'd be able to bore and sleeve the block to 427 bore.
Justin
If you're REALLY willing to throw some money at it, ask them if they'd be able to bore and sleeve the block to 427 bore.
Justin
Post Fiend
Joined: Mar 2004
Posts: 6,056
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From: Union, Washington
I was able to go .080" once on a 390 to make a 406 (4.13") out of it. But that was a 390 HP block from the early '60s. Otherwise, unless you check the casting thinkness and sonic test, I wouldn't try it. The 428 blocks (4.13") were 105 blocks so it would be worth checking though.
Post Fiend
Joined: Jan 2003
Posts: 8,600
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From: Iowa
Get your block sonic checked. That's the only way you'll know for sure.
I did the drill bit test on a couple "mirror 105" blocks I've got sitting out in the garage. I then calculated that, assuming absolutely no core shift, they could be safely bored to 4.23". But what are the chances of that? Not too high...
I did the drill bit test on a couple "mirror 105" blocks I've got sitting out in the garage. I then calculated that, assuming absolutely no core shift, they could be safely bored to 4.23". But what are the chances of that? Not too high...
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