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Thread: 421 or 434?

  1. #1
    Senior Member RACING JUNKIE
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    Feb 2006
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    Lenoir City Tennessee
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    865

    421 or 434?

    im going to be ordering my crank tuesday. im using a stock 400 block. i want to build either a 421 or 434. is there less clearancing with the 421? i dont want to weaken the block anymore than i have to. do i have to run a small base cam with both? id really like to do the 434 but not sure if the block will last to long.ive got brodix track1 heads 228 intake runners 2.08 intake 1.60 exhaust valves. probably around a 630 to 660 lift roller cam. 750 aed carb 4500 stahl 350 turbo with brake. not sure what gear yet probably a 28 or 29 inch tall tire. what gear would you recomend? what kind of times do you think it will do? i run 1/8 mile.oh yeah thinking about some small dome pistons. 11.5 to 12.1 ? any help would really be appreciated. possibly some NOS to

  2. #2
    Senior Member RACING JUNKIE
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    Coldwater, MI
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    IMO your taking a chance going that big with a 400 block, I've seen people do it and have good luck but then others who broke several blocks before they decided to get a aftermarket.
    I still love a 406 :lol: I had a 434 in one of my cars, small base circle is almost a must.
    David Lanning
    IHRA NHRA 387B

    Fleenor Racing Transmission
    419-280-1406
    Lanning Electric
    Complete Drag Car Wiring
    APD Race Engines
    www.apdracing.com

  3. #3
    Senior Member EXPERT BUILDER
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    Aug 2007
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    Orient, OH
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    we had a 406 that ran a best of 9.76 and we built a 434 that was the same parts and it ran a best of 9.68... I think it ran 6.14 best in the eighth at 3200 pounds with a 4.86 gear 32" tire.

    both motors were almost the exact same heads, cam, compression, intake, carb. We ran a 1050 dominator on gas.

    The 434 we ended up half filling the block and it was a little harder to cool down between rounds than the 406.

    If it were me I would build the 421. you have little to no clearancing to do and the best bang for your buck in a stock block.

    I hope this helps.
    Josh VanHorne

    1964 Chevy Nova
    Worlds quickest and fastest tow truck. (9.92 @ 137)

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  4. #4

  5. #5
    Senior Member RACING JUNKIE
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    I'd go with the 421" like other said very little clearancing on the blk, also if you run Eagle rods, they use 7/16" rod bolt heads which helps even more on the clearancing. We have a couple 434's with stock blks and so far no problems, in fact the stock block is quicker than the after market 434" by a tenth 4.80's VS 4.95 in 2 different dragsters, but it's filled to the water pump opening and we run a main girdle.
    You will have to run a small base circle cam with either one 421" or 434" and some cam companies call .925 dia a small base circle, but in reality you'll need to be below .900 dia. My 434" Bullit cam is .875 in a dart little "M" blk.
    4.86 sounds good with a turbo 3.50 trans, if it were a PG, i'd go 5.13 or 5.29 gears, for the 1/8 mile runs only.

    JMO

    Zip.

  6. #6

  7. #7
    Senior Member MASTER BUILDER
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    Oct 2003
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    144
    The new Compstar rods, have rod bolts that have to only be clearanced a little on stroker motor 434 cid.

  8. #8

  9. #9
    did you find the made in china tag in the box.

  10. #10


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