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ive bee told .60 You can not bore it to a 427, or 428. About the only thing you can do is take a 428 crank, and install it, and that will give you a 410.
 

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Most 390's can be bored safely .080" to 4.130" which is standard bore for a 428.

The cylinder walls should be "sonic mapped" to detect any thin areas due to core shift or corrosion.
 

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Ford recommends a maximum overbore of .060" (to 4.110") but I've seen FE's of this type safely bored to 4.130" as long as a sonic check of the block didn't contraindicate boring to this size...

Then, you could use a 410/428 crank and get 428 ci...

Otherwise, the aforementioned bore/stroke combo is your maximum...

IMO, increasing the stroke will provide a better performance benifit than increasing bore, given the parameters of this combo...

Good luck!
 

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My .02...IIRC there was a story about this same topic approx one year ago in Mustangs and Fords in a write-up about a featured 67 GT500 car. The feature car came with a "428" which tests showed was a over-bored 390, article mentioned this was not allowable. However, they mentioned a 352 block could be safely bored to a 428.
 

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However, they mentioned a 352 block could be safely bored to a 428.

As the 352 is a 4.00" bore block, IMO, the same cautions about sonic checking would apply, considering the overbore would be .130"

I've heard that early blocks, like the 352's, had thicker cylinder walls but I've never confirmed this personally.

Thanks for the tip on the article...
 
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