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how do you tell the difference between a 350 and 400 engine?

Discussion in '1973-1991 K5 | Suburban | Truck' started by 89 Blazzer, Jul 17, 2001.

  1. 89 Blazzer

    89 Blazzer Registered Member

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    What are things to look for? I bought a piece of $$$$ Blazer for the rims. It was cheap. The owner thinks it has a 400 in it. It is not the original engine. It is out of an early to mid 70's truck or van and has the large spark plugs also.
     
  2. FARTMAN

    FARTMAN 1/2 ton status

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    if it is a 400 it will have a groove cut out in the front balancer also will have a balance weight on the flywheel. also some 400 had 3 freeze plugs per side. get them the casting#off the block behind the head on drivers side on top of block and i can tell ya fer shure. BEANS A NATURALLY LOW FAT FOOD this message brought to you by the national bean growers assn. i think
     
  3. bablazer73

    bablazer73 1/2 ton status

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    the freeze plugs are a good giveaway and check the counter weights on the balacer and flywheel. These are getting very scarce and are also getting valuble. I sold one on ebay that needed work(spun bearing) for 300.00. I paid 50.00 for the truck it came in!! I have a book of casting #'s. If you can get the casting # off the back of the block, I can tell you more about it. The casting # is on the drivers side of the block back where the bellhousing bolts up. 2 bolt blocks are better than 4 bolts on these blocks.

    your right. I don't understand the jeep thing!
     
  4. blazer72

    blazer72 1/2 ton status

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    All 400 blocks have the numbers 509 cast in both sides of the block, this and casting numbers are the only sure ways as I have seen 400's with 350 flywheels and/or balacers, Also seen 350's the other way around
     
  5. FARTMAN

    FARTMAN 1/2 ton status

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    hey dude i thinks you need to wake up and smell the gear oil. ALL 400 BLOCKS ARE NOT 509 CASTINGS!!!!!!!!!! THERE IS SOME OTHER # FOR 400 small blocks, but they best i.d is the casting # BEANS A NATURALLY LOW FAT FOOD!!!!!!!
     
  6. MRBIGBLOCK

    MRBIGBLOCK 1/2 ton status

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    hey now seems that the old smelly dude is right the 400 s.b. has other casrting# 3951511 this is 1970-74 2bolt mains or 4 bolt u must pull the pan to confirm, here is another 400 #is 330817, the 509 block was 79-80 the last years for the 400 it did have 509 cast 0n the sides also that is the last 3 digits of the casting # also some bow tie racing blocks were produced.
     
  7. blazer72

    blazer72 1/2 ton status

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    HEY DUDE All I know is what I read in the chevy casting book. Its says it not me, It does not say most it says all have the upside down 509 on both the left and right sides. Both of the blocks I run have this on them and it does not match the casting number. The casting book reads as if the 509 on the side of the block is not part of the casting number always. With that said all of the known 400 blocks I have seen and the 10 I haved had plus the 2 I am curently running and the 3 I have stored have the 509 cast in the sides. Of them only 2 came out of 79 Vans. So there may be some out there that don't but if they do, then they are 400's for sure. SO if you have a block that is said to be a 400 look first to see if it has the 400 balancer, its a bit hard to see the flywheel in most cases. But if you can check is to see if there is a balance plate or externaly blananced flywheel (not easy to see with it bolted on). If you get theis far the look at the sides 400 had both 2 and 3 casting plugs/frezee plugs so look for the 509 behind the mounting lugs. If you get this far or dont but still think it is a 400 you needed to check the numbers to make sure. GM has done many strange things that no one under standes.

    K5

    <P ID="edit"><FONT class="small">Edited by blazer72 on 07/18/01 08:45 AM.</FONT></P>
     
  8. 88streetblaze

    88streetblaze 1/2 ton status

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    forget the casting numbers look at the number of freeze plugs. three is a 400 HOWEVER the ones in the center on both sides can just be a casting pertrusion that is the same size of a freeze plug..
     
  9. Pure Insanity

    Pure Insanity 1/2 ton status

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    I've always been told the freeze plugs theory is an old wive's tale. I don't know for sure. Just what I've been told.

    If a balancer or flywheel from a 400 and 350 are interchanged, it'll have a vibration. ALL 400's are externally balanced and ALL others are internally balanced.

    Out of 100,000 sperm, YOU were the fastest?? [​IMG]
     
  10. smp

    smp 1/2 ton status

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    The freeze plug ID thing is crap i have a 71 400sb 2 bolt main with 2 freeze plugs and i did conferm this with casting numbers the only dead giveaway on most 400's is the large notch in the dampner all 400's are externally balanced from the factory. But it could of been rebuilt and internally balanced or could have the wrong balancer. The only sure way to ID it is to check the casting numbers(as if you havn't allready been told[​IMG] ) Here is a web site that breaks down the casting numbers and location : <a target="_blank" href=http://www.mortec.com/>http://www.mortec.com/</a>

    [​IMG] [​IMG] [​IMG]
     
  11. FARTMAN

    FARTMAN 1/2 ton status

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    hey dude u are on crack not all 400 has 3 freeze plugs,get a life. the beaner strikes again!!!!!!!!!!!!
     
  12. smp

    smp 1/2 ton status

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    I forgot something else if it has a large notch in the balancer it could also be a stroked 350(377,383,386 ect..depending on over bore) because it uses the unbalanced 400 crankshaft there for you would need to use the 400 flywheel / flexplate and dampner.

    [​IMG] [​IMG] [​IMG]
     
  13. 88streetblaze

    88streetblaze 1/2 ton status

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    no not all have three freeze plugs but those that do not have a round pertrusion(that means it sticks out for any dipshits out there) that is the same shape and size as a freeze plug right smack in between the two it does have.. like i said i my first post.
     
  14. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Good call SMP! Keep in mind that you can put a 400 crank in a 350 for a 383... or a 350 in a 400 for a 377!!! And if you do this, you must use the correct corresponding balancer and flywheel! Someone who knows their engines!!!!

    I also have to agree that the freeze plug thing is bogus. I have seen 2 and 3 freeze plug engines at the same swap meet! Both models do exist.

    The only sure fire way to be sure is to get the casting numbers from the rear-top-drivers-side of the block itself. Then check that number@ http://24.10.209.54/bigolk5.htm [​IMG]
     
  15. Waxer

    Waxer 1/2 ton status Author

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    I wouldnt say thats the final say. I have seen mistakes on mortec so I dont trust it 100%. The ONLY sure fire way to tell what you have is to pull the pan and measure the bore of a cylinder. Then you know if its a 350, or if its the 400.

    Crawlin the rocks with my K5
    <a target="_blank" href=http://www.rockreadyk5.com>http://www.rockreadyk5.com</a>
     
  16. 88streetblaze

    88streetblaze 1/2 ton status

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    waxer got a point.. but who cares about 400's anyways. they are notorious for cracking their heads. way back in the day when i rebuilt one in auto mechanics it took four sets of heads to find a set that wasn't cracked.
    nothing is better than a well built 350 'cept maybe a well built 383..........
     
  17. FARTMAN

    FARTMAN 1/2 ton status

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    i think you guys are total stinking idiots!!!!!!!!!!!!!!!!!!!!!! YOU DONT HAVE TO PULL THE PAN A CHECK THE HOLE SIZE TO TELL WHAT IT IS!!!!!!!!!! i think you all must be FORD HEADS!!!!!!!!! wake up people there are dozens of books and resources available for breaking down chevy casting numbers not only can u tell what size it is u can tell the date it was made right down to the hour and alot of times where it was made!! the stamped i.d. # will tell ya what it was originally installed in,the horse power rating,and emission controls installed if any, also for your information in drag racing circles also dirt track the 400 is considered a lot better than ant 350 or 383 also if ya get good heads they r not bad about crackin so you need to get better informed or GO BACK TO THE JUNKY OLD FORDS!!!!!!!!!!!!!!!!! THE BEAN EATER HAS STUCK AGAIN!!!!!!!!!!!!!! beans a low sodium food this message brought to you by the great northern bean producers.assn. i think
     
  18. FARTMAN

    FARTMAN 1/2 ton status

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    waxer dude has sniffed too much crack!!!!!!!! i think pull the pan yea RIGHT HAHAHAHAHAHAHAHAHH!!!!!!! THE BEANER HAS STRUCK AGAIN!!
     
  19. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    PULL THE PAN???? Someone must be bored...

    Why not tell them the bore size too?

    350= 3.750" (stock)
    400= 4.000" (stock)

    I only offer Mortec because I have personally never seen any problems with their lists. If someone else has, then maybe it would be worth while for you to find a second opinion in a GM performance book or other reference.

    Besides, what really is "final say" in this world anyhow?!!!

    Does anyone else smell BFGs burning???
    454/TH400/NP205 - 14BFF/D60/w/ 4.10s
    <a target="_blank" href=http://24.10.209.54/bigolk5.htm>http://24.10.209.54/bigolk5.htm</a> [​IMG]
     
  20. Andreas

    Andreas 1/2 ton status

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    Uhmm...the sb400 has 4.125" bore and 3.75" stroke. The sb350 has 4" bore and 3.48" stroke.

    /Andreas

    406cui of pure sh*t[​IMG]
     

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