400 SBC vs 454 BBC

Discussion in 'Engine & Performance' started by BigBlackChevy77, Oct 28, 2018.

  1. WHEELMAN

    WHEELMAN Full Access Member

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    Sweet Jesus help us all.a 400 hundred block.are you crazy.through that block away.take it to the scrap metal yard.a 400 block is good for nothing.it is bored out and has simeze cylinders.

    Do you even know what that means.look straight across one side to the end.no meat.in between the cylinders

    For the head gaskets to seal.they blow holes.stright across.from one cylinder to the other they want take any heat.they blow.and never ever.try to use one.for a boat engine.

    It's 350 small block or 454 big block use the big block.if engine bay is no problem.you are welcome
     
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  2. WHEELMAN

    WHEELMAN Full Access Member

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    There is no such thing as a 400 big block.it is a bored out 350 small block.we had one in a brand new 1971 Chevy impala.it lasted the warenty.like 12,000 miles and after that.it would over heat.all the time.lock up thermostat,s.

    Look at a 400 block.you will see that they are no good.for nonthing.unless you just like wrenching all the time
     
  3. bucket

    bucket Super Moderator Staff Member

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    I had a 400 with a Holley on top of it. I loved it...
     
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  4. BigBlackChevy77

    BigBlackChevy77 Junior Member

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    Yea I can see that the cylinders are siamesed along with little meat to them compared to my 454. Doesn't mean it's a bad motor just have to be careful with it. I am planning on using the 454 but the 400 will probably go in a smaller car for drag racing or street/strip.
     
  5. MikeB

    MikeB Full Access Member

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    When you went from SBC to BBC, were you able to use the same engine mount frame brackets in the same location--the ones bolted to the frame? On my 250 six to 350 conversion, I was able to re-use the originals, but had to relocate them to a different set of holes to maintain the proper driveline angle and to place the radiator fan in the center of the shroud.

    For anyone interested, I have many of the part numbers for frame brackets and clam shells for various years, models (K and C), and engine combos. In the GM parts books, frame brackets are called "BRACKET, ENG MT FRM". The clam shells are called "BRACKET, ENG MT".
     
  6. MikeB

    MikeB Full Access Member

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    Lots of dirt track racers would disagree with you. Back in the 1980s-early 2000s, they snatched those things up like crazy at junk yards. They would make incredible TQ and close to 500 HP, and last for a few seasons (probably just as long as a higher revving 350).

    I suggest Googling terms like "400 small block RPM potential" or "400 small block dirt track" to find thousands of posts from 10-20 years ago. For a street truck engine, I think 350 HP along with massive TQ (20%-25% more than any 350) can be achieved reliably with a 400. Now if the OP just has to have 400 HP at the expense of TQ, then that means more revs and more money, so a BBC would be best, IMO.

    I didn't notice that the OP said his block had been bored. If you meant a 400 is a bored 350, then you didn't realize the 400 cylinder walls are much thicker. Kind of like 327 and 302 cylinder walls are thicker than 283 walls.
     
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  7. rpcraft

    rpcraft Full Access Member

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    I would tend to lean towards the Big block for reliability and ultimate torque/power potential. As previously mentioned, the 400 in stock trim was prone to overheating and simple issues that never made it a legendary motor. If given the alternative to a mildly built 350 and a stock 400 I'd take the 350 over it, just simply because so much more can be done to improve upon it with mild work. The same can be said about the big block.
     
  8. DirtyDYT

    DirtyDYT Full Access Member

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    I reused the frame side engine mounts without any changes. I also reused the bbc engine side clamshells up top. I wasn't sure if I could do that at the time but I asked a could of local "Chevy guys" and people on this forum. Turns out it was a super easy swap besides mistakes I made due to lack of experience (like not having a dual pattern flex plate to mate to the TH350).
     
  9. Mad gimp

    Mad gimp Junior Member

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    454 vs 400? Throw the 400 block out in your junk and ill come get it. I love them 400's

    1535344820402_101.jpg
     
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  10. Mad gimp

    Mad gimp Junior Member

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    Other than outside dimensions there is very little similarity between a 350 and a 400. A 400 is externally ballanced and a 350 is internally ballanced. A 400 has larger main bearing journals. The bore and stroke of a 400 is nearly identicle to the bore and stroke of a 402 big block. So i disagree with a 400 hundred being nothing more than a bored out 350. Did gm have cooling issues with the first few years they built the 400? Yep. Ive built 3 400 and the last one i built is the only one i can get that will run warmer than 200° but its also bored .030 and has 11&1/2 to 1 compression and has no steam holes drilled in the heads as stock 400 cylinder heads do. It will only heat up if i let it idle for extended periods of time. The last 406 i built i couldnt get it to run past 200° even beating the crap out of it in a 83 silverado pulling a car trailer
     
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  11. MikeB

    MikeB Full Access Member

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    My 250 six to 350 swap wasn't as easy. Went through two sets of clam shells before I found the right ones! Also, had to lengthen or shorten many of the electrical wires. Nice to know the SBC to BBC swap is a little easier.
     
  12. MikeB

    MikeB Full Access Member

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    Guess you didn't get the e-mail about it being total crap. :rolleyes:

    Gotta wonder how many people that bad-mouth the 400 actually had one? Or did they have one with aftermarket heads w/o steam holes drilled?

    Personally I had a 400 2bbl in a used 1976 station wagon, and the odometer probably showed >70K miles when I sold it. Never had an issue with it, even in that giant family truckster full of kids and luggage.

    Also had a neighbor with the 4bbl version in a mid-1970s Monte Carlo. That thing rocked. It had noticeably more power than the 350s available in the Monte Carlo that year.
     
    Last edited: Nov 14, 2018 at 11:29 AM
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  13. Mad gimp

    Mad gimp Junior Member

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    The 400 has gotten a bad wrap. And yeah like is said the 406 i run in my monte has after market heads and i did not drill the steams holes..it will get up to 210 to 220 IF and only if i let it idle for a long time. This 406 isnt big in the horse power department but its a monster in low end/ midrange torque. I push this 406 alot harder than the last one i built. I shift it a 6200 rpm. 400 were never designed for rpm like that but this has scat forged crank 6" scat forged rods and forged weisco pistons and its all been ballanced so i aint affraid to beat on it a little well i mean pretty much when the ignition key is on lol
     

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