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Thread: 421 sbc

  1. #1
    Member MASTER JOURNEYMAN
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    421 sbc


    Guys
    I am building a new 400 block from scratch. I want to build a 421 CID with a 4.155 bore and a 3.875 stroke.

    I am looking at a Wheeler kit with their 4130 forged crank, wheeler forged 4140 rods, with forged flat top pistons. The price is not out ragious at $1400.00

    Has any one use their stuff? If so what is your opinion of it.
    If there is someone you have used please let me know.

  2. #2
    Senior Member RACING JUNKIE
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    You may want to consider when you bore that 400 block they have a tendancy to split cylinders when you bore them that much. The little M block is just around 1400.00. A very good investment.

  3. #3
    i have run 40 over 400 blocks for years thats 4.165 bore only one i had crack was after 5 years of abuse and nitrous lots of nitrous450 shot off the line all the way through the quarter

  4. #4
    Senior Member DYNO OPERATOR
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    It seems like to me the only people that don't like 400 blocks are the people thet NEVER ran them.

    No body says MY 400 broke at this point.

    ?????????????????????
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  5. #5
    Senior Member EXPERT BUILDER
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    I have machined alot of 400 blocks over the years and they seem to have the more problems with cranking in the webbing, decks, cylinders ETC then theh 350 blocks we have machined.

    Here is a quote from another builder.
    Quote Originally Posted by bill jones
    -one thing they need to do is sonic test the bores up and down the bores right under each of the 5 head bolt holes per bore----because there is 5 vertical grooves up and down the bores inside the water jackets.

    -those grooves are actually the thinnest segments of the bore walls----and they tend crack vertically when high cylinder pressures happen against the bore walls.

    -I measured a lot of 400's years ago and found some of these notches to be as thin as .101" to .129"----BUT good notches should average around .186" thick----and good bore walls should average out at about .238" thick.

    -I also found that cylinder #6 was always the thinnest and #5 cylinder was the next thinnest.

    -400 blocks with casting #330817 have the thinnest walls and are only about .189" average thickness.

    -the thickest bore walls I ever found were on the early 1969 to 1972 four bolt main blocks---but those blocks were always weak in the main webs and needed splayed main caps and then fill the empty main bolt holes with some sort of special threaded fastener and use loctite to lock it in there.
    --------------------------------------------------------------------------
    -here's link back to a discussion a few years ago that might be of interest.

    http://www.speedtalk.com/forum/viewt...e953f6d3e44f9b
    ----------------------------------------------------------------------------
    -sonic testing a stock SBC 400 for a 600HP application is a very tedious job and really should have a map made of each cylinder.

    -I seriously doubt that you'd get more than 4--maybe even 8 numbers per bore-----but really that's not enough----it takes way more time to get the entire picture than most people would ever spend.
    Here is a good link to look over
    http://speedtalk.com/forum/viewtopic...&highlight=400
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  6. #6
    Senior Member RACING JUNKIE
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    All there saying is to throw caution to the wind, be advised that its a crap shoot using a 400 that big.
    JMO> Cp
    ***IN GOD WE TRUST***

  7. #7
    Senior Member DYNO OPERATOR
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    The one's that broke how much power were they making? To make a genaral statement that there no good is CRAZY .

    Not all of us out here can afford to build max horsepower motors or have the chassie to be safe at that speed. ops: :cry:

    can you see core shift with your eye and a flash light?
    :shock:

    just a few ?
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  8. #8

    400 blocks

    There have been three that split cylinders around my group of racer friends here. They were all three bracket racers with carbs and no nitrous. One was a fresh motor that was a Lunati crank and pro mod rods motor and he felt the same way as you guys did about the GM blocks because he had good service till then. That block collapsed about the 15th run and took out everything but the heads. It was .040 over with 12:1 compression. I dont know why people are so quick to take it as such a insult that someone makes a possible helpful statement but he is right, hes not making a comment about someones wife or children here! I would run the GM block in a street motor, but based on facts, I will not run them on a race engine anymore. To costly in event of a failure.

  9. #9
    Senior Member EXPERT BUILDER
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    Quote Originally Posted by montecarlo84
    It seems like to me the only people that don't like 400 blocks are the people thet NEVER ran them.

    No body says MY 400 broke at this point.

    ?????????????????????
    I have machined alot of 400 blocks for other shops and engines builders only to see them fail after a season or two,

    Its hard to make chicken soup out of chicken shyt.
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  10. #10
    Senior Member EXPERT BUILDER
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    Quote Originally Posted by montecarlo84


    can you see core shift with your eye and a flash light?
    :shock:

    just a few ?
    Only with a sonic tester
    WWW.CNCBLOCKSNE.COM
    IS A DIVISION OF
    HINKSON AUTOMOTIVE
    RESEARCH & DEVELOPMENT

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    EMAIL [email protected]


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