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crank question

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by 72blazer4x4, May 22, 2001.

  1. 72blazer4x4

    72blazer4x4 Registered Member

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    if i put a 400 crank into my 350, what does it make it? how would i make it a 383?

    jeremy
     
  2. Roostr84

    Roostr84 1/2 ton status

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    Well that would make it a 383 but you also have to change the pistons and clearence the block. If you have done all this you should be fine, if not you have some work and money outlay ahead of you.

    Chris =)
    http:// www.roostr84.coloradok5.com
     
  3. Burt4x4

    Burt4x4 3/4 ton status

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    That is the original way to make a 383Stroker. Now a days there are a few 383 cranks out there that don't require grinding the block.
    Here are a few sites with some great info. I have a 350 block in my garage that someday will be a 383.
    http://www.beckracing.com/store/nph-shop.cgi
    http://www.scatcrankshafts.com/index.html
    Good Luck

    72K5[​IMG]Led Zeppelin[​IMG]Rock ON![​IMG]
    <A target="_blank" HREF=http://www.burt4x4.coloradok5.com>http://www.burt4x4.coloradok5.com</A>
     
  4. 2quicK5

    2quicK5 Registered Member

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    Since the 400 is an externally balanced crank, you will also need a balancer and flywheel (or flexplate for auto) for a 400. Since the stroke has changed you will need new pistons with a shorter compression height so that the piston will not stick out above the block deck surface. You can get pistons that will work with either the stock 400 5.6" rods or longer aftermarket rods. The 400 main bearing journals on a stock 400 are also larger diameter than the 350 crank, so you will need to get these turned down or get special main bearings. Summit Racing has some good inexpensive 383 stroker conversion kits that include the crank, rods, pistons, bearings etc.

    John

    1972 K5 Blazer: 400 ci, 4 sp, 3" lift, 35" Tires

    2000 Trans Am, A4
    11.97@114 mph
     
  5. Steve_Chin

    Steve_Chin 1/2 ton status

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    Good summary above, but I'd interject that because the 400 main journal is larger than the 350 main journal, there is no bearing that will make the 400 crank work in a 350, which means you need to cut the mains.

    Personally, I don't like externally balanced cranks, so I would go with an aftermarket fully-counterweighted crank with the correct main journal sizes. Also, because of the reduced crankpin overlap (due to the longer stroke and smaller main journal combination), I'd go with a forged crank or an ArmaSteel crank at the very least. Of course, I tend to wind my engines out a bit and feel much safer with a slightly more expensive crank because of the extra margin of safety it would provide.

    Oh, the other thing is that at 0.030" overbore, it would be a 383. At 0.020" it's a 381. At 0.060" it's a 388.
     
  6. 72blazer4x4

    72blazer4x4 Registered Member

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    thanx guys, im learning alot. as soon as i get out of school i want to rebuild my engine and i was thinking about just making it a 383.

    jeremy
     
  7. 2quicK5

    2quicK5 Registered Member

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    Jeremy,

    It would probably be easier and cheaper to just buy a used 400 small block and rebuild it instead. Why have a 383 when you can have a 406 or 409 for less $$$ ?

    John

    1972 K5 Blazer: 400 ci, 4 sp, 3" lift, 35" Tires

    2000 Trans Am, A4
    11.97@114 mph
     
  8. R72K5

    R72K5 Banned

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    Bingo! couldnt have said it better than that :)

    '72 K-5 4x4, CST, 3.07, 4 speed, NP 205, 31' x 10.5", Olive green and primer, rusted out, rice smasher!
     
  9. kiley

    kiley Registered Member

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    What makes a 406 or 409 cheaper than a 383?
     
  10. 2quicK5

    2quicK5 Registered Member

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    A rebuilt 400 (406, 409 etc.) would be cheaper because you wouldn't have to buy the expensive stroker kit that you would need to turn a 350 into a 383.

    John

    1972 K5 Blazer: 400 ci, 4 sp, 3" lift, 35" Tires

    2000 Trans Am, A4
    11.97@114 mph
     
  11. Steve_Chin

    Steve_Chin 1/2 ton status

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    "Expensive stroker kit" = A 400 crank with machining to cut the main journals down (my least favorite option) or a custom-made 3.75" stroke crank with 350 sized main journals, plus custom pistons (pin height and ring stack change for the stroke), plus small base-circle camshaft. If you're going with 6" rods, then you need to ad the cost of the special rods in to the equation as well. I'm planning a 381 based off of a forged crank, 6" custom rods, and forged custom pistons. It will be a couple of years until I do it since my 357 is still relatively new and runs pretty well.
     

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