427 vs 396 block
Thread Starter
Racer
Joined: Aug 2006
Posts: 493
Likes: 1
From: yarmouth ma
427 vs 396 block
i am in the market for a 427 block. one of my friends told me i can use a 396 if i find one as the exterior stampings are the same. Ofcourse I would need to bore it and change out the crank etc...
any thoughts on this theory? 396's should be easier to find.
thanks
any thoughts on this theory? 396's should be easier to find.
thanks
Le Mans Master
Joined: Aug 2003
Posts: 7,720
Likes: 12
From: Chattanooga TN
Actually 396 and 427 share a common crankshaft. I do not believe you can bore it that far, others may correct me but I believe you will have too thin cylinder walls if you do that. 454 blocks are not that hard to find. I have one.....
Burning Brakes
Joined: Dec 2003
Posts: 1,149
Likes: 153
I don't think you can bore a 396 to 427,not positive though. Why not a 454 block to 427,done all the time.I've done it,in fact I just brought one from a forum member and I know he's got another one.e-mail me and I'll give you his phone #
Melting Slicks
Joined: Mar 2007
Posts: 2,100
Likes: 12
From: Frederick Maryland
If it's not the original block, then it's not correct regardless of casting date. Since it won't be original anymore, just drop in a 454 and set it up with an appropriate induction system.
It's only original once...after that there's no point in trying to keep it that way unless you want it correct looking.
It's only original once...after that there's no point in trying to keep it that way unless you want it correct looking.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
A smaller bore was used in the first 396s to meet the limited to 400 c.i. GM policy. So the early 396s are said to be able to be bored out for 427.
See
How The Corvette Got The BB http://ganeys.home.sprynet.com/77facts.htm
See
How The Corvette Got The BB http://ganeys.home.sprynet.com/77facts.htm
Thread Starter
Racer
Joined: Aug 2006
Posts: 493
Likes: 1
From: yarmouth ma
Hi
Please don't make any assumptions about my plans, this was a real 427 car and thats what I plan on putting back in there. I plan on keeping the car and I will be restoring it in the next few years, so I am just trying to get some of the missing pieces that I need.
Please don't make any assumptions about my plans, this was a real 427 car and thats what I plan on putting back in there. I plan on keeping the car and I will be restoring it in the next few years, so I am just trying to get some of the missing pieces that I need.
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Limping across the line
Joined: Oct 2002
Posts: 5,299
Likes: 109
From: Peoria Az
427's were built using a 454 block and a 396 crank.
You MIGHT be able to bore a 396 block out to 4.125 to make it a 427 but you casting numbers wont agree. You need a casting number 3916321 or 3935439 for a 68 427 block.
If you really want a 68 dated 396 block I have one and I'm in need of a 71 454 block.
A great site for number help is Mortec.com
You MIGHT be able to bore a 396 block out to 4.125 to make it a 427 but you casting numbers wont agree. You need a casting number 3916321 or 3935439 for a 68 427 block.
If you really want a 68 dated 396 block I have one and I'm in need of a 71 454 block.
A great site for number help is Mortec.com
Last edited by AzMotorhead; Nov 30, 2007 at 11:59 AM.
Instructor
Joined: Apr 2007
Posts: 206
Likes: 0
From: Bardstown Ky
Melting Slicks
Joined: Nov 2006
Posts: 3,400
Likes: 1,813
From: Apple Valley, MN
Your car will be worth a lot more with the correct casting number and corresponding casting date (preceding your car's production by ~ 2 months). If you're not concerned about originality, then why not just go the the General for a 572 and kick up some serious mayhem?
Le Mans Master
Joined: Nov 2006
Posts: 5,262
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From: I'd like to propose a toast... to internal combustion and wind in the face.
Melting Slicks
Joined: Sep 2006
Posts: 3,381
Likes: 2,604
From: Burning Jet-A
I think what you meant to say was that you were very concerned with the appearance of originality. Originality is or it is not. As for the 69 427 you probably need a 3963512 block...What do you have regarding the original engine option for the car?
http://cgi.ebay.com/ebaymotors/1968-...spagenameZWDVW
As for friends telling you the exterior stampings are the same, well, they may be good friends. They have no clue about late 60's BBC engine block castings. All blocks are different, and even within casting numbers there are detail differences. You may need to consult with an expert to build you what you want.
http://cgi.ebay.com/ebaymotors/1968-...spagenameZWDVW
As for friends telling you the exterior stampings are the same, well, they may be good friends. They have no clue about late 60's BBC engine block castings. All blocks are different, and even within casting numbers there are detail differences. You may need to consult with an expert to build you what you want.
Last edited by international blue; Nov 30, 2007 at 04:10 PM.
Instructor
Joined: Dec 2004
Posts: 236
Likes: 0
From: Clearwater Florida
Genrally speaking, the Mark IV BB was first available in 1965 as a 396 which had a 4.094 bore.
The following year, the 396 was bored out to make a 427. The 427 used a different counter weighted crankshaft because of the weight difference in the pistons. The 427 bore was 4.251
The second version of the 396 was the 402 which had a bore of 4.125. GM still referred to this motor as a 396.
The 396, 402, and 427 all had the same 3.76 stroke.
In 1970 they stroked the 427 to make the 454. The 454 had a 4.00 stroke.
The following year, the 396 was bored out to make a 427. The 427 used a different counter weighted crankshaft because of the weight difference in the pistons. The 427 bore was 4.251
The second version of the 396 was the 402 which had a bore of 4.125. GM still referred to this motor as a 396.
The 396, 402, and 427 all had the same 3.76 stroke.
In 1970 they stroked the 427 to make the 454. The 454 had a 4.00 stroke.
Burning Brakes
Joined: Jan 2007
Posts: 1,057
Likes: 4
From: Concord Calif
It would not be a good thing to try to bore a 96 that far. The two bolt block will not make it no matter what. but I have done a few of the four bolt blocks and they worked. The four bo;t blocks have a muck thicker cylinder, this is only talking about the 396 blocks. still don't try it!
Drifting
Joined: Sep 2007
Posts: 1,572
Likes: 51
From: Wichita Kansas
If it's not the original block, then it's not correct regardless of casting date. Since it won't be original anymore, just drop in a 454 and set it up with an appropriate induction system.
It's only original once...after that there's no point in trying to keep it that way unless you want it correct looking.
It's only original once...after that there's no point in trying to keep it that way unless you want it correct looking.
and Big different in restoration and original. Nothing wrong with his plan. I never read any thing about restamping the block. He is just restoring to period correct.