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  #1  
Old Oct 20th, 11, 7:32 PM
chevyl69 chevyl69 is offline
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alex
 
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Default 396 bored to 427?

I was wondering if anyone has bored a 396 to a 427? I know its possible to do this. But i dont want to waste a good 396 block to do it. So i was wondering if anyone had done it. Thanks
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  #2  
Old Oct 20th, 11, 8:23 PM
tpshea tpshea is offline
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Default Re: 396 bored to 427?

I'm not really a big block guy, but that would be .125" to go from a 402 to 427. It would be .155" from a 396. It seems like a lot to me. I found one casting number on Mortec , 3855961, that was common to both 396 and 427.

Here is the link to Mortec --> MorTec Chevy V-8 Big Block Casting Numbers
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  #3  
Old Oct 20th, 11, 8:29 PM
tpshea tpshea is offline
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Default Re: 396 bored to 427?

Alex,

You might get more activity on your question if you put it in performance. I think it can be moved there, but I don't know how. Just a thought.
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  #4  
Old Oct 20th, 11, 8:48 PM
chevyl69 chevyl69 is offline
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Default Re: 396 bored to 427?

Tim, Thanks for the info.
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  #5  
Old Oct 20th, 11, 9:08 PM
SWHEATON SWHEATON is offline
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Default Re: 396 bored to 427?

From what i understand the 961 bbc was the only block that GM used for production 396 & a limited amount of 427s in late 1965 into 1966 when the 427 introduced . (maybe 67 too but not sure of that)

BTW,not all 1965-66 961 bbc 396 & 427 blocks were able to handle the larger 427 bore,they need to be sonic tested 1st.

Another supposed way to confirm if 961 block was able to go to 427 bore was if you can't get a std size pencil inbetween the cyls in water jacket when trying it thru freeze out plug hole in a 961 bbc block it meant the cyls were thicker alowing for the 427's larger bore.

But i have never expericned that for myself ,i had a 66 961 spare motor (396) with 840 heads approx 12-13 yrs ago with L78 intake,steel crank,dimple rods with large bolts,etc.

I sold it to a guy restoring a 66 chevelle ss 396/360hp 4spd for $600,paid $125 for it 10yrs prior so did ok on it.

Other then the 961 block other 396/402 blocks would not normally safely handle the larger 427 bore when using a stock 396/427 crank /stroke to achieve it & not a stroker crank to make for ex a 434 bbc stroker motor from a 396 or 402 bbc block.

Scott
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1969 CHEVELLE SS396,ORIGINAL #'S MATCH,GOT IN 1978,(In 2001 rblt/bored original 396 .030 to 402)/M20/12BOLT/3:31'S
2006 YAMAHA 1700 ROADSTAR SILVERADO (1 owner ,GOT in 2009,4,700 miles/WK end fun)
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2002 MAXIMA (DAILY DRIVER/1 owner,GOT 3/2013 w-44k miles)
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  #6  
Old Oct 20th, 11, 9:16 PM
SWHEATON SWHEATON is offline
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Default Re: 396 bored to 427?

Quote:
Originally Posted by tpshea View Post
Alex,

You might get more activity on your question if you put it in performance. I think it can be moved there, but I don't know how. Just a thought.
================

Engine forum is a good place for this post,not off base IMHO.

Scott
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1969 CHEVELLE SS396,ORIGINAL #'S MATCH,GOT IN 1978,(In 2001 rblt/bored original 396 .030 to 402)/M20/12BOLT/3:31'S
2006 YAMAHA 1700 ROADSTAR SILVERADO (1 owner ,GOT in 2009,4,700 miles/WK end fun)
1977 KAWASAKI KZ1000 (AM ORIGINAL OWNER ,GOT IN 1977,NOW has 29k miles/WK end fun)
2002 MAXIMA (DAILY DRIVER/1 owner,GOT 3/2013 w-44k miles)
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  #7  
Old Oct 20th, 11, 9:20 PM
Buster Buster is offline
 
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Default Re: 396 bored to 427?

I've had done it to two 396 blocks in the 1980s. Worked out good for me. Some two bolt 396 blocks were built with 427 castings. Some 4 bolt 396 also had very thick cylinder walls.

You should at the very least inspect the block for core shift. If it looks reasonable than you will need to do the "pencil test".

Remove the center freeze plug. If a normal yellow pencil will NOT fit between the bores in the water jacket than it should work out for you.

I used a 66 two bolt and a 67 or 68 4 bolt block to do the two I did.
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  #8  
Old Oct 20th, 11, 9:24 PM
jvoiles jvoiles is offline
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Default Re: 396 bored to 427?

Don't waste the block, use a 454 from the 70's with the 396 internals. I did this and it has worked out great.
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  #9  
Old Oct 20th, 11, 10:12 PM
novaderrik novaderrik is online now
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Derrick
 
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Default Re: 396 bored to 427?

Quote:
Originally Posted by jvoiles View Post
Don't waste the block, use a 454 from the 70's with the 396 internals. I did this and it has worked out great.
that won't work with about .5% of the people that will ever look under the hood if you're trying to disguise a bigger engine as a stock 396..
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  #10  
Old Oct 21st, 11, 7:20 AM
Busted Knuckles Busted Knuckles is offline
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Default Re: 396 bored to 427?

A pencil will always fit between the bores, even on a 289 casting 454 block.
On a 427, 454 or thicker 396, it just BARELY fits - there's around 1/4" or less between the cylinders. On a run-of-the-mill 396, that gap is a lot closer to 1/2".
Have it sonic tested. One thing for sure, it won't have clearance for a stroker crank, you'll have to do some grinding.
I'd find a solid 454 casting and someone who needs the 396 for a resto build. Even if you bore it .125, that's gonna cost you some coin from your builder, it takes a while to cut that much out of each cylinder.
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  #11  
Old Oct 21st, 11, 8:00 AM
bracketchev1221 bracketchev1221 is offline
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Default Re: 396 bored to 427?

If it were me, I would find a 454 block and use the 396 crank and rods. Now you have a 427. A 396 isn't bad either. Unless you plan on going to the track with it, they all will spin the tires on the street. And 500 hp out of a 396 is faster than most realize.
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  #12  
Old Oct 21st, 11, 12:32 PM
mkube396 mkube396 is offline
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Default Re: 396 bored to 427?

stroke the 396 with a 4.00" or a 4.25 crank
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  #13  
Old Oct 21st, 11, 1:29 PM
ss3964spd ss3964spd is offline
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Default Re: 396 bored to 427?

I tried to do the same thing.

I have a 961 2 bolt block from a Feb '66 assembled 1966 Impala - numbers matching to the car, making it a late '65 or early '66 block (I forget the casting date).

The block was already .060 over and the machinist advised that the cylinders didn't have enough thickness to go to 4.250.
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  #14  
Old Oct 21st, 11, 1:39 PM
chevyl69 chevyl69 is offline
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Default Re: 396 bored to 427?

Thanks to all for the input, the reason im even wondering about this i cant get a 427 without breaking the bank. The blocks are even just to expensive. Its either going to be a bored 396 or a 454 block. Unless someone cuts me a deal on a vintage 427. 396 and 454 blocks are more in my price range. Wow have things gone through the roof. Thanks Guys
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  #15  
Old Oct 21st, 11, 2:02 PM
70-SS454 70-SS454 is offline
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Default Re: 396 bored to 427?

454 Block & internals w/a 396 crank will get you a 427...cheaper way to go...
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