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400 small blocks

Discussion in 'The Garage' started by SwanGuy, Oct 16, 2002.

  1. SwanGuy

    SwanGuy Registered Member

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    I recently blew up my 350 and now am considering replacing it with a 400 small block, what should I know about this motor before I go and pick one up?
     
  2. Sandman

    Sandman 3/4 ton status Author

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    They do not like high RPM as much. Thats what killed mine. They also need a good radiator as they like to heat up more. Other than that, I liked mine. Gave me years of good service. Oh, yeah. Get the flexpate for it. the 400's have externally balanced ones and will not interchange with the other small-blocks.
     
  3. SwanGuy

    SwanGuy Registered Member

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    You mention flexpate, what does it look like and what does it do? When it comes to motors I know very little. As far as tranny's go, I can rebuild 350's and 400's with my eyes closed...ha!
     
  4. Sandman

    Sandman 3/4 ton status Author

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    Its the big round thing that bolts to the crank. the converter bolts to this (if automatic). Hope this helps.
     
  5. Sandman

    Sandman 3/4 ton status Author

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    Thats back of the engine not the front. Thats the balancer. You'll also need that as it is different than the other small-blocks.
     
  6. SwanGuy

    SwanGuy Registered Member

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    Oh...ok, the flywheel. Yeah, that comes with it. Now I've heard about them overheating, I have a 84 Chevy 3/4 ton. The grille, core support, and radiator have been swapped in from an 89-91 Chevy Blazer, is that radiator going to have sufficient cooling power?
     
  7. Sandman

    Sandman 3/4 ton status Author

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    See if its a three or four core. Four your fine. Three, you might be fine. Might just have to run it and find out.
     
  8. Z3PR

    Z3PR Banned

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    I've got a 400 small block in my 76 Blazer. Great motor, no complaints other then it's a small block and not that big block RamJet 502 I've been drueling over !!!! My 400 has just under 80,000 miles on it and is running strong. /forums/images/graemlins/k5.gif
     
  9. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    besides headers and exhaust I have a bone stock 400 and I love it. I have a 3 row radiator and haven't had a problem as long as you keep fluid in it.
     
  10. BorregoK5

    BorregoK5 1/2 ton status

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    I run a stroked 400 at 9.5 c/r with a 4 core radiator. Good torque and lots of grunt power. I'm running the stock 350 small valve heads with a pocket port and drilled the steam holes for the 400 block. In fact I'm running almost all the 350 external components other than the long block, flexplate and balancer. The engine will run hotter than normal with extended high load high rpm use (pulling a heavy trailer up a steep grade rev'd high in a low gear), other than that it always runs around the thermastat setting. Great compromise to running the heavier big block.
     
  11. Sandman

    Sandman 3/4 ton status Author

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    I agree. The only reason I went BB is because I fried the 400.
     
  12. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Turn it into a 377 destroker and really turn some RPMs. From what tinkering I've done on these programs, a 350 seems to put out more power per cubes than a 400. 400s' torque is insane though, it'll do in a 383.

    The only thing that will be a pain is getting it work with bigger rods. The 400s used 5.56" long rod which creates a higher side load on the bores and wears them out faster. You can get them to run 5.7" rods with the appropriate pistons and a little clearancing on the rods. Then get a good radiator and you won't hear a peep. Oh, and maybe internal balanced stlye crank wouldn't hurt either. Every damn motor is expensive.
     
  13. balzackks84

    balzackks84 1/2 ton status GMOTM Winner

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    400's kick a$$. I loved mine in my 74 jimmy on 38's. It had 4.10s and would fry the tires like there was no tomarrow. I never had an overheating problem with mine till the water pump went out. If you do build one post what you did and if you like it cause i wanna build another one.
     
  14. Z3PR

    Z3PR Banned

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    I know there is a stroker kit for the 400 sbc, I just can't remember what it brings it up to. 400's have good torque to start with, but the stroker kit is suposta be even better yet.
     
  15. RaisedK5

    RaisedK5 1/2 ton status

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    THe popular strokers for a 400 are 415, and 427. thats alot of cubes out of something that (relativly) small. Im going to be building a 406 (overbored) soon, just got it on the stand for dissasembly, so im pondering what route to take also, oh well, only time and my wallet will tell what she becomes. /forums/images/graemlins/grin.gif
     
  16. bablazer73

    bablazer73 1/2 ton status

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    If you can, stay away from the 4 bolt 400 blocks. They are actually weaker. A good rad is a must. they run alot hotter.I would consider the destroke or long rod conversions. The rod angle is what kills these engines. Klien racing makes a 454 stroker for them. also, for the record, A FLEXPLATE is for automatics and a FLYWHEEL is for standard tranny's!!
     
  17. Z3PR

    Z3PR Banned

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    That's the one I was thinking of getting. The 415 stroker kit.
     
  18. bigmack

    bigmack 1/2 ton status

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    If you decide to go with a 400 you will not regret it. I had a 3 row radiator in mine and it would heat up a little on long uphill runs, but I now have a 4 row radiator with a good fan and it never gets above 190 degrees, it usually runs about 160. I built mine about 6 months ago and it has been absolutely great, when me and my friends are out riding and someone gets stuck to the point where a truck with alot of nuts is needed who do you think they always look to ? /forums/images/graemlins/cool.gif
     
  19. Mreetz

    Mreetz 1/2 ton status

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    I'm puttin a 400 in my soon. Anyone have any leads on a place to find a manual flywheel for it in the Denver area?
    /forums/images/graemlins/1zhelp.gif
    Thanks.

    Marty---
     

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