having a mini stroke

Discussion in ''Da Nailhead' started by gsgtx, Nov 18, 2010.

  1. gsgtx

    gsgtx Silver Level contributor

    got the crank back had it off set .055 gives it a 3.75 stroke, comes out to 444ci. in old posts i guess you can get 460ci or 464ci out of them. mines just a mini stroker.
  2. gsgtx

    gsgtx Silver Level contributor

    .055 x2. i think its 2.10 bbc rod with sbc rod bearing. i will know more today going to the machine shop.
  3. gsgtx

    gsgtx Silver Level contributor

    .055x2=.110 +3.64=3.75. let me talk to the shop i will post later
  4. Gary Bohannon

    Gary Bohannon Well-Known Member

    The offset must be multiplied by 2 because the crank moves from BDC (that's one) to TDC (thats 2) so the piston went that much lower, then it went that much higher, which doubles the total length of the stroke or piston travel.

    That's assuming the .055 is referring to the actual amount on each crank throw.

    (& That's assuming the crank WILL rotate after being torqued, of course.)
  5. wilber

    wilber Well-Known Member

    What connecting rods do you use?
  6. 425 2X4 Nailhd

    425 2X4 Nailhd Well-Known Member

    The actual off-set is doubled to add to the overall stroke.
    Rod journal diameter would have to be reduced to a common size bearing.
    Smaller diameter means LESS Frictional losses too.
    Since these Nailheads are not revving to 10,000 you have more than enough strength in the Factory Forged Cranks.
  7. Schurkey

    Schurkey Silver Level contributor

    3.64 OFFSET GROUND .055 undersize is not equivalent to 3.64 offset by .055.

    3.64 offset ground .055 undersize = 3.695 stroke

    3.64 stroke offset .055 = 3.75 stroke, but it would take a .110 undersize journal. (Actually, it would require a bit more than .110 undersize in real life.)

    No. The offset is always doubled, but the offset is 1/2 (at best) the amount of journal undersize.

    I'll send you my PayPal account info. ;>)

    It all depends on whether the original poster has a genuine .055 offset, or whether he has a .055 undersize journal--and I'm not clear which it is. A micrometer would tell the tale.

    Grinding a journal .055 undersize would normally mean taking a cut .0275 deep, all the way around the journal. The cut is half the diameter reduction. If the cut is concentric with the original journal, no offset is incurred.

    Offset grinding is the art of taking a variable-depth cut, and getting the "light" and "heavy" cut where you want them--but the OFFSET is the same distance as the average cut--.0275.

    The offset is always doubled when calculating stroke. The problem here is that Kitabel is confusing "undersize" and "offset". Easy to do, they're related, offset is 1/2 the undersize (theoretically) but is doubled to calculate stroke. Therefore, in theory, the STROKE INCREASE is the same as the UNDERSIZE. But the OFFSET is 1/2 the UNDERSIZE.

    The offset is 1/2 the amount of diameter reduction AT THEORETICAL BEST. In actual practice, the offset will be just slightly less than 1/2 because the machinist will "waste" some of the offset in order to assure that the journal is ground ALL the way around. Because the offset is slightly less, the stroke increase also is slightly lower than "theoretical best".
  8. Steve Reynolds

    Steve Reynolds SRE Inc


    Attached Files:

  9. SpecialWagon65

    SpecialWagon65 Ted Nagel

    Good info!
    I just purchased a nailhead crank that is .5 increase in stroke...stock rods, custom pistons with the pin relocated .5 up. Its going to be fun clearing the inside of the block for this action! It is a kit...dated 1962...balanced with flywheel and harmonic balancer...heavy!
  10. Steve Reynolds

    Steve Reynolds SRE Inc

    Forgot to mention.
    The diagram above is not to a specific size engine, it's just meant as an example.

  11. gsgtx

    gsgtx Silver Level contributor

    ok here it is, the crank was welded and ground off set .055. 2x that gives you a stroke of 3.75. the crank was also turned down to 2.10 from 2.25. using bbchevy rods, they make them with the big end 2.10 same as sbchevy. using small block rod bearings. rod lenght is 6.535.
  12. wilber

    wilber Well-Known Member

    Who makes the connecting rod with a center to center of 6.535"
  13. Schurkey

    Schurkey Silver Level contributor

    Common in the (aftermarket) Chevy world. 6.535 is .400 longer than a common BBC connecting rod at 6.135, exactly what's needed when using passenger-car pistons in a tall-deck (big Truck) style block which has a .400 higher deck.
    Last edited: Nov 20, 2010
  14. gsgtx

    gsgtx Silver Level contributor

    the machine shop has some used ones i will ask what brand.
  15. gsgtx

    gsgtx Silver Level contributor

    i was wrong he did not weld the crank. could have went as much as .075 off set. crank turned to 2.099 width 1.943 rod width .964 had to take .028 off the sides of the rods.reversed the rod bearing halves. they are oliver brand rods.
  16. wilber

    wilber Well-Known Member

  17. wkillgs

    wkillgs Gold Level Contributor

    Just round it off and call it a Wildcat 445 engine!
    Interesting build, keep us informed of the progress!:TU:
  18. gsgtx

    gsgtx Silver Level contributor

    i am an old mopar guy 3.75 stroke is the same for a 440 chrysler,444 is a 440 .020 over. like you said i like the 445 wildcat better.lol
  19. roostriz

    roostriz Well-Known Member

    Good luck with it! I would have liked to snap it up but I have too many other projects at the moment.
  20. gsgtx

    gsgtx Silver Level contributor

    up date on the engine,doug at the machine shop had to go .035 over to clean up one of the cyl,tried to keep it at .028 over didnt work out. he also wanted to full the block[block filler] to the bottom of soft plugs,should help strudy the cyls. the je pistons will end up being .012 thousand in the hole. comp will be 10.1 to 1, last engine was 9.75 to 1. pin height is 1.59. weight of piston 650 grams. very light for nailhead pistons. he didnt like the old flex plate,orderd one of the new repros.hope there good. with the .035 over it ends up with 446 ci. its been cold and a lot of snow here in upstate n.y. this project helps the winter to go by. also helps your money to go by, lol

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