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383 vs. 400

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 1bad82k5, May 10, 2001.

  1. 1bad82k5

    1bad82k5 1/2 ton status

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    While we are on the subject of 383's, other than the heating problems with a 400, why would you build a 383? I have a couple 400's sitting around just dying to be rebuilt. There are two ways to look at a 383 - adding stroke to a 350 or taking bore from a 400. Does one have advantage over the other? Just a thought, any info would be greatly appreciated.
    thanks
    eric

    Hell, it don't really matter....it's just for my race car.
     
  2. DieselDan

    DieselDan 1/2 ton status

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    If you got a 400 that the bores aren't scuffed to hell rebuild it (with a better 5.7 350 rod). The problem with the 400's was the short rod that GM used. Made for a really poor rod to stroke ratio. Even better is a 400 block 350 crank combo (377 CI w/030 over). Much better in the efficiency department; the 383 is known as a torquer because it doesn't breathe that well. Not that a 383 won't cook (it can!).

    This outta get the embers burning.
     
  3. CaptCrunch

    CaptCrunch 1/2 ton status

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    383's are torque and the 377's are for higher rpms. I'm not a fan of 400's mostly because they seem to lack torque for the cid of the block. It is kinda just like a 350 powerwise unless you do some serious mods such as cylinder heads or are looking to wind up to 8 or 9 grand w/ some serious lower end parts. I would rather add a bit more size and weight and take 396 BBC and pull some tree stumps out [​IMG] . I rarely see a plainjane 400 anymore... they all are varing cid displacements and stroked.. oh yeah and the worst thing in my mind about the 400 is the siamessed (sp?) bores that love to give cooling problems and blown head gaskets.

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  4. Triaged

    Triaged 1/2 ton status

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    For the 383 it depends on bore stroke ratio. If it is a stroked 350 than it will have alot of torque and a limited RPM range. If it is a destroked 400 it will make alot of high RPM HP but not much low end torque (not good for a heavy 4x4).
    I have a 400 and no cooling problems.
    Pistons cost more for a 400 than for a 350/383.
    Like was said earler go with the 350 (5.7") con rods.
    The 400 is harder to find pistons w/ low compression ratio (esp. w/ 350 rods).
    Oh I almost forgot "There is no replacement for displacement".

    '71 Blazer CST with alot of rust
     
  5. Triaged

    Triaged 1/2 ton status

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    I don't know how my 400 was built but it has a s%it load of low end torque (I do know 350 heads were used). I have enough power to peel out the rear w/ 33" tires and 3.73 gears.

    '71 Blazer CST with alot of rust
     
  6. Ryeguy

    Ryeguy 1/2 ton status

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    Nothing at all wrong with a 400, so long as you keep it cool.

    --Rob
     
  7. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    ....

    Been digging through the archives and this one's got me interested. Does anybody have any numbers or facts. I've a 350 '89 block and an early 70's 400 and can't decided. I don't do much wheeling to be honest. Alot of the little in-town road races against junior with his 4 cyl and overdone stereo. I'm tired of being the slug, lol. I got a set of 3.73s all done up to go in with my 31"s. I need to hop up the motor now.

    <a target="_blank" href=http://www.geocities.com/bigkern76>http://www.geocities.com/bigkern76</a>
     
  8. Andreas

    Andreas 1/2 ton status

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    Why do you guys insist on saying (writing) "377 is a high revving high horsepower machine"?? It´s a 350 crank in a 400 block, so it´s able to outperform the 350 horsepowerwise AND torquewise. Build a 350 and a 377 to the same specs and the 377 will win.

    I just built a 5.7" rod 406 but considered building a 377 before setteling on the 406. Never thought twice about a 383. Reason is the big bore in a 400 block and it´s advantages when it comes to breathing.

    Oh well...... I´m off. Gonna chew on some old valvesprings now[​IMG]

    /Andreas

    406cui of pure sh*t[​IMG]
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    Only "facts" I've seen, (I think it was in HP Books How to Build SBC's or some such) were that the 400's tended to "wear out" faster than a 350. (according to how many warranty problems GM had with them)

    If I had the book here now, I would quote what the writer said, but something about the 400 piston side load on the cylinders causing greater wear. More than likely this is due to rod length (guessing here) as the writer emphasized that the 383 fixes the problem. FWIW

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     
  10. ftn96

    ftn96 1/2 ton status

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    Im no BIG engine guru, but from what I understand the 400 is getting close to extinct aminly for the fact that it didn't keep it popularity amungs the peeps due to its tendency to have over heating problem. Which from what you said D about the excessive wearing on the cylinder walls. This sounds like a 2+2=4 to me.
    As far as the 383, well it may very well be a more torquey motor than the 400, but there again it sounds like something that is more capable of giving problems down the road.
    I think it reliability come to play more so than the amount of power or ponies from an engine. Yeah, you might be able to whip my ass off the line or at anything else until the day when your 383 or glowing red 400 pukes and my 350 starts right up and takes a licken and keeps on tickin.
    **Personally** for a wheeler or a daily driver I'd stick within a motors resonable limits without having to do TOO much modifying to make it work, again.. as the more you modify seems like the more work you end up doing in the long run. Much the same as the lift kits, the tires, the gears, the driveline angles, the crossover steering, the ...etc etc. etc...
    Seems like once you start you never finish.
    I personally like the mildly built 350. It may not be as fast or ballsy as the 383 or the 400. But I'd bet all the odds in Las Vegas that it would last longer than either of the other.
    **Again, this is my logical mind speaking, not my engine guru expertiece, as if I really had any.
    Who's next on the soap box?[​IMG]

    Surgeon General's Warning:
    Viagra and steroids may be harmful to your spouse![​IMG]
    <a target="_blank" href=http://www.nashvillek5.freeservers.com>www.nashvillek5.freeservers.com</a>
     
  11. 79k20

    79k20 1/2 ton status

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    i would never build a 377 for a 4x4 where low end torque is needed. chevy HP did an article called 377 vs. 383. the 383 ruled with low end power, and the 377 only made 13 lb-ft more torque at 6300 rpm. my truck doesn't spend much time at 6300rpm, and personally i would build a 406 over either. built right a 406 can be a torque monster.

    sean

    79 k20(duh) d44, 14bolt, built 350,350,np203,9"lift
     
  12. Triaged

    Triaged 1/2 ton status

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    How about this <a target="_blank" href=http://home.earthlink.net/~triaged/383_vs_406.gif>383 vs. 406</a>
    This w/ Vortec heads, 9.5:1 CR,
    Isky 202 dur .450 lift Cam, and 2.5" Dual Ex. on both motors


    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
    <a target="_blank" href=http://community.webshots.com/user/triaged>See it Here </a>
     
  13. 79k20

    79k20 1/2 ton status

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    man i want a 406 bad, their awesome. i'm just waiting for my 350 to give me a reason to replace it.

    sean

    79 k20(duh) d44, 14bolt, built 350,350,np203,9"lift
     
  14. Triaged

    Triaged 1/2 ton status

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    Oops...that was w/ a roller cam in the 406...it is correct now.

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
    <a target="_blank" href=http://community.webshots.com/user/triaged>See it Here </a>
     
  15. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    YOU KICK A$$! Thanks man, thats exactly wanted to see. I really wanna get that program. I downloaded a demo but for some reason they think that I'm school girl and have Ford 302. Its the default motor for that demo. Where'd you get that program from?

    Well with that being stated....How in the heck do you fix the 400. I've heard that rods were way to short and caused to much side load on the cylinder walls.

    <a target="_blank" href=http://www.geocities.com/bigkern76>http://www.geocities.com/bigkern76</a>
     
  16. 2cocky

    2cocky Registered Member

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    not a big deal i can spin my 33's with 3.73 gears and i'm running a goodwrench 350 with a cam change, intake and headers. nothing special but it halls a@@

    OOOPS....I THINK I JUST RAN OVER YOUR JEEP THING!!!!!
     
  17. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Mikey, It seems you've never been involved with a 400 SBC project that had enough camshaft and headflow for the engine size. There's 20% more motor than a 350 there, you need 20% more of everything else too.

    There's no REplacement for DISplacement, and there never will be.

    Triaged, basically what you posted totally contradicts what I said earlier in this post--you can't compare a smaller motor to a bigger one if they have the same heads and similar camshafts.

    The bigger one needs more airflow--airflow is the name of the game when engines are nothing but glorified air pumps.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  18. Triaged

    Triaged 1/2 ton status

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    Try this <a target="_blank" href=http://home.earthlink.net/~triaged/ea30.zip>Engine Analyzer</a>

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
    <a target="_blank" href=http://community.webshots.com/user/triaged>See it Here </a>
     
  19. dyeager535

    dyeager535 1 ton status Premium Member

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    For example (going with your head change scenario) this was just posted on the Monte list I belong to:

    "350 ci
    9.2 CR
    Hydraulic roller cam:
    Int. Exh. Int. Exh. Centerline
    214 220 .452" .465" 112
    1.94" intake valve, 1.50" exhaust valve heads
    Edelbrock TES headers (1.5" primary)
    WND 7525 single plane intake w/ EGR (probably pretty
    close to a performer RPM)
    (Q-Jet)

    Then just change the heads to Trick Flows w/ 2.02/1.6 valves and see what that looks like"

    This was for someone to mock up in Desktop Dyno 2k, and this was the response:

    "With the stock heads, you got the following results:

    RPM Power Torque
    2000 148 388
    2500 189 396
    3000 232 405
    3500 272 408
    4000 296 388
    4500 295 344
    5000 282 296
    5500 254 242

    With the TW
    2000 150 394
    2500 194 408
    3000 241 422
    3500 290 435
    4000 333 437
    4500 369 430
    5000 391 411
    5500 389 372
    6000 372 325
    6500 344 278


    The difference is plain ;-)"

    Now again, this was destined for a car, so those heads/setup are not going to be the "right" solution necessarily to what he is going for. BUT it illustrates what good heads can do. Along the same lines, I notice though that *for the cost* the TF heads don't appreciably increase torque, which is really what you are shooting for with a big motor. "over cam" it and you'll have a slow ass truck off the line with tons of top end.

    Again, that illustration was just for comparisons, and in no way indicates the difference between a 383 and 400.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     

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