400 SB or 402 BB?
Thread Starter
Instructor
Joined: Sep 2007
Posts: 123
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400 SB or 402 BB?
im going to be replacing my blown engine soon (76 l48) and found a guy with a lot of good engines for really cheap. He has a 400 small block ready to run with 80k. also for " a couple hundred" bucks theres a disassembled 402 which would probably make good power. Is the 402 a gem? should i get it and put it back together? Also do i need specific "Corvette" big block engine mounts if i did swap the 402? Thanks for any input!
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
Your mounts will work with either. You could make quite a bit more power with the BB 402 than the SB 400. The difference is in the heads and valve sizes.
But if you switch to BB you have to change a lot of other parts to make the swap.
But if you switch to BB you have to change a lot of other parts to make the swap.
Le Mans Master
Joined: Feb 2006
Posts: 6,048
Likes: 5
From: "cutesy" TN
Both will need parts (flywheel for the 400 SB)(brackets and pulleys for the BB).
The frame may need a dent put in it to put the BB in it (don't know I've never owned a 76 but you need to check NOW).
I personally would go with a big block, it just looks better than a small block.
The frame may need a dent put in it to put the BB in it (don't know I've never owned a 76 but you need to check NOW).
I personally would go with a big block, it just looks better than a small block.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Can't miss with the power of a BB. BUT as stated, all the brackets are different, the crossmember may need some work, and you'll need to redo the exhaust. And then you get to find out the next weakest link. You'll get to do that either way
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Unless you are trying to maximize torque/power for your car [if so, you would be talking 540 cubes or more...], the BB is the way to go. If not, then stay with a maxxed-out version of the SB and you can still install it with the brackets/etc you already have. {what the heck is a 402 BB? a bored-out 396? That sound like an exercise in futility if you can just stick in a 400 block.}
Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
Stick with the small block. It's a good bit lighter than the big block which will help with handling.
Unless you're dealing with a numbers matching situation, there's really no reason to use a 396, the "baby" of the big blocks. 454 at least, 496 is fine and 540 is better, yet. They all take up the same space under the hood, why not get the most you can?
Unless you're dealing with a numbers matching situation, there's really no reason to use a 396, the "baby" of the big blocks. 454 at least, 496 is fine and 540 is better, yet. They all take up the same space under the hood, why not get the most you can?
Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
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Melting Slicks
Joined: Jun 2002
Posts: 2,844
Likes: 99
From: Orrtanna Pa.
I tell everybody mines a stock 350 after I blow their doors off.......
Seriously, one of the reasons I stuck with a small block is that over the years I had accumulated quite a bunch of aftermarket goodies for a smallblock. Be it valve covers, intakes, headers, etc. By selecting the 406 I was able to reuse everything.
Be carefull though,....If you go down the path I did, you will need to upgrade a lot of things that will begin to break........
Seriously, one of the reasons I stuck with a small block is that over the years I had accumulated quite a bunch of aftermarket goodies for a smallblock. Be it valve covers, intakes, headers, etc. By selecting the 406 I was able to reuse everything.
Be carefull though,....If you go down the path I did, you will need to upgrade a lot of things that will begin to break........
Last edited by The Money Pit; Apr 9, 2009 at 08:51 AM.
Drifting
Joined: Feb 2005
Posts: 1,879
Likes: 38
From: Los Gatos CA
396 was the displacement in 1965. Later it was a marketing term (SS396) as the displacement was 402 cu in. Once upon a time it was large displacement, but not now. If you want a BB, do a BB not a 402. Just my 2 cents...
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
What is your budget and goals? Is it a stock 400? If so you are looking at putting a 30+ year old used engine in with no signifigant power difference. The 402 needs rebuilding anyway. If you put the $ from rebuilding the 402 and buying pullies and accesories for the 402 into rebuilding what you got into a 383 or 396 or, better yet get a later model 4 bolt main, 1 piece crank factory roller block and build that to a 383 or 396 with a set of brodix IK200's you have 450 plus hp, tons of torque, lighter weight and will be much happier in the long run. This can be done for close to the same $ as installing that 402. JMHO
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
Iron intake to the pan for both engines small block is 520 lb big block 680 lb, if you were going to keep stock heads on both engines the oval port big block heads would be a lot better for breathing air, but if your willing to spend the money for new modern heads for the small block to let it breath the small block would keep you from changing front coil springs, buying all the brackets be lighter in weight. The small bore ( for a BB ) 396/402 just does not have the potential for power of other big blocks hard to come up with parts to even stroke it, if you were going to go big block you would be much better off finding a 454 out of a pick up truck rebuilding it there were gillions of them put in pickups.
Last edited by Little Mouse; Apr 9, 2009 at 10:33 AM.
Instructor
Joined: Jul 2007
Posts: 228
Likes: 0
From: Price Utah
I would stay with the small block unless you have a ton of money and could go with one of the big inch BB. Do some careful math. Many people are very successful with the old 400 sb but you said it had 80K on it. Has it been rebuilt? What heads, cam etc? Take a look at the GMPP site. I would
look closely at the price of a new motor vs. someone elses "ready to go motor" Their are some very experienced engine builders on this site. Ck out what they have to say. Good luck
look closely at the price of a new motor vs. someone elses "ready to go motor" Their are some very experienced engine builders on this site. Ck out what they have to say. Good luck
Pro
Joined: Feb 2009
Posts: 589
Likes: 1
From: PA
Hmmm, okay my 2 cents worth. Go with the 402. You can make as much HP and torque you want in it. I seen 1 guy here mention front springs and yes you'd need them. I didn't see anyone mention transmission. I'm guessing your 76 is a Turbo 350. If ya make a higher HP engine like in the neighborhood of 400, you'd need to beef the 350 trans up or get a Turbo 400.
I say go for it, but I'm a BB guy and love em. Put a 427 or 454 decal on the air cleaner and your set.
I say go for it, but I'm a BB guy and love em. Put a 427 or 454 decal on the air cleaner and your set.
Racer
Joined: May 2008
Posts: 318
Likes: 0
From: Wheaton, Illinois
The 400sb also has some issues with machining and tapping the pads on the block. I think one of them is for the four speed bracket that goes between the block and the frame and something else? Anyone know?
Instructor
Joined: Aug 2007
Posts: 241
Likes: 5
From: NC
400 SBC.. Put a cam in it, and a intake on it with headers and its a fun ride. 400hp 400lbs. want to go to the next step, add heads and a better cam.. 500/500. If its got hypertech junk pistons, don't pull it over 5500. You really wont need to if you are not trying to race street/strip. There are plenty of BB's that are dogs. Just because its a big block doesn't mean it runs hard. Ask the guy with the 427/400 that got whip'd by my LT-1 350. 