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Thread: 425 nailhead Crankshaft strength

  1. Question 425 nailhead Crankshaft strength

    I have not been able to find after market forged cranks for the 425. How much power can a stock crank handle?

  2. The stock 401/425 crank and rods are forged. They were often used in supercharged engines over 1000 HP. The cast pistons are the weak link in the Nailhead.

    Mickey Thompson made a stroker crank for the 401/425 that you see for sale on the web every so often. I had seen a custom stroker 401/425 made by by King recently. I attached a picture of that crank. It is in the 470 CI range.
    Attached Images Attached Images
    Last edited by Dr. Frankenbuick; 08-22-2009 at 02:13 AM.
    Steve B.



    67 GS 525 Buick Stage IV
    66 GS Convertible
    65 GS HT
    63 Riv
    02 Subaru WRX Turbo
    03 Ford Cobra Convertible (Factory Supercharged)

  3. The M/T and King crank are cast and are not as strong as the stock crank. If you want to build a stroker. have a machine shop offset grind the crank and run BBC rods. You will get int the 450 c.i. range depending on the bore.

  4. Some have used the 401/425 cranks in 455 Buicks to be able to spin the engines to 7 & 8000 RPM's. There is someone now that will offset grind a "Nail" crank for use in another 455 Buick engine offset grinding the rod journals to 1.88", Honda size, for additional cubes.

    Tom T.

  5. To All:

    I must be missing something.

    Why add the extra Cubes when the heads don't flow well with 425 cubes?

    Are there any new/re-designed Heads out on the Market? (Please say yes!) ;-)

    Thanks,

    Ty O'Neal

  6. they may not flow well, but more cubes is still more cubes.

    plus, you can always solve the flow problem with forced induction.
    The way to crush the bourgeoisie is to grind them between the millstones of taxation and inflation.
    Vladimir Lenin

    Government schooling is about "the perfect organization of the hive."
    H.H. Goddard, Human Efficiency (1920)

  7. Quote Originally Posted by tyoneal View Post
    To All:

    Why add the extra Cubes when the heads don't flow well with 425 cubes?

    Thanks,

    Ty O'Neal
    The ported 364/401/425 head can flow as well as a stock unported 455 Stage 1 head. Then bigger is better. Also, as Bob said, there is always forced induction to make the head flow less of a problem.
    Steve B.



    67 GS 525 Buick Stage IV
    66 GS Convertible
    65 GS HT
    63 Riv
    02 Subaru WRX Turbo
    03 Ford Cobra Convertible (Factory Supercharged)

  8. Go back to my post. I was talking about using a "Nail" crank in a 455 Buick!!! When you force induct the intake the exhaust now becomes the problem. It just cannot get out fast enough. Will make some serious power & torque to 4500 or so RPM's though.

    Tom T.

  9. Quote Originally Posted by telriv View Post
    Some have used the 401/425 cranks in 455 Buicks to be able to spin the engines to 7 & 8000 RPM's. There is someone now that will offset grind a "Nail" crank for use in another 455 Buick engine offset grinding the rod journals to 1.88", Honda size, for additional cubes.

    Tom T.
    Wow!
    I hope this info doesn't get out to all the 455 guys. It's hard enough to find a good Nailhead!
    Boy, Buick really messed up when they designed the 400/455.....they should have just made new heads for the Nailhead! Why mess with a good design????
    Walt
    65-66 GS's

  10. Why mess with a good design????

    well, partly it was to move to lightweight casting techniques. i believe the tall deck Nails weigh north of 700lbs compared to the ~625lb of the BBB.

    also, they converted the big block to the integrated aluminum timing cover, oil pump, water pump like the small blocks had.
    The way to crush the bourgeoisie is to grind them between the millstones of taxation and inflation.
    Vladimir Lenin

    Government schooling is about "the perfect organization of the hive."
    H.H. Goddard, Human Efficiency (1920)

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