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Discussion Starter · #1 ·
It's common knowledge that a 396 '961' block can usually be safely bored to 4.25

How about the 68 '3935440' casting? I'm aware that sonic checking must be done but does anyone have knowledge that a 440 block is a decent choice for 4.25 bore?
 

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wouldnt it be easier to start with a 454 block? Jim
 

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The 961 blocks came from the factory as 396 & 427 in 65 & 66,see below:

Scott

3855961....396.......65-66...2 or 4 bolt
3855961....427.......66......2-bolt
3855962....396.......65-66...4-bolt
 

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Mike,maybe your mistaken,in the past i have seen the 961 blocks written about in other publications on those 961 396 motors as being able to bore to 427 because the cyls were thicker on some of the 961 blocks for 65 & 66 only depeding on when they were cast in thoses 2 yr's.

Dont shoot the messenger(Me),this is not me comming up with this info,i have read it written by other professional engine builders and somewhere in some of my old GM books/literature/articles too over the yrs about GM using the 961 blocks for both the 396 & 427's in 65 & 66. I tend to believe it because that info was coming from GM & reputable engine builders and i have also heard of a couple peolpe actually doing it yrs back but i never personally took a 961 396 block out to a 427 bore.

But even then i would still have any 961 block sonic tested & checked throughly by a qualified machinest thats very experienced with doing this type of testing & boring before i would try to bore a good 961 block out 427 to avoid poss reuining the block.

Scott
 
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Ed Staffel say's he made a 454 out of a 1966, 396, -961 block.

He write's he didn't have to grind it anywhere.

And that said, Off the topic!!

I figure my '75 454 P/U block that swallowed my 496 rotating assembly with NO grinding at all except to notch the tops of the cylinders and to touch the oil pump nut area up WILL swallow a 4.375" crank with minimal grinding to create a 510.6" engine!!

pdq67

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The 440 396 block is a 68 vintage for 396 only and likely would not be safe to take out to 427,but maybe if it passed sonic testing but dont bet on it.

Scott
 
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