2 keyed cranks
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2 keyed cranks

  1. #1
    Senior Member slotracer's Avatar
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    Default 2 keyed cranks

    is it always needed or is there a h.p. amount or % of boost when it has to be done?
    slot
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    I do one single 1/4" keyway on everything I have ever built. Never a problem.
    Some guys cut the 1/4" key slot right over the existing key slot. Others go 180 degrees from that and cut for a single 1/4 key.

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    Quote Originally Posted by Fiat48 View Post
    I do one single 1/4" keyway on everything I have ever built. Never a problem.
    Some guys cut the 1/4" key slot right over the existing key slot. Others go 180 degrees from that and cut for a single 1/4 key.
    Fiat...so you say a single 1/4" keyway is enough, or you add a single 1/4" keyway and still use the stock one? What you posted above sounds like both. I'm cornfuzed.


    For what it's worth, I have 7" Romac steel SFI balancers with double keyways availablbe.
    Last edited by scott foxwell; 12-30-2007 at 06:15 PM.
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    Senior Member slotracer's Avatar
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    i bought a dc 8-71 blower and now am finally getting around to building the engine i brought the pulley to the shop to get everything balanced and there is only one keyway. so it sounds like i will be all right then. do i make the keyway 1/4" or is it that size already? its on a bbc
    slot
    87 eliminator
    next boat ??????????????
    new owner of the redneck yacht club
    Stockton, ca.

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    BBC has 3/16 stock.

    I always cut 1/4 key opposite the stock key.

    But... not my own stuff, it's going to a customer and the extra cannot hurt.

    Some stuff comes with 2 1/4 keys and you have no choice but to do something.

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    steelcomp was here
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    Quote Originally Posted by Infomaniac View Post
    BBC has 3/16 stock.

    I always cut 1/4 key opposite the stock key.

    But... not my own stuff, it's going to a customer and the extra cannot hurt.

    Some stuff comes with 2 1/4 keys and you have no choice but to do something.
    Cutting a keyway is half of it...do you broach the hubs or balancers too, or do most of what you use already come with 1/4" slots?
    I don't know about you guys, but getting two keyways to line up correctly is a PITA.
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    I mean single key is enough. Tho it is easier( because it is easier to locate the mill) and just go over the 3/16 and make it 1/4....I prefer to do it 180 from that. So I just run one single 1/4" and forget about the stocker 3/16 key.

    Blower hubs are either broached already with one single 1/4 key.....or 2 1/4 keys....or one 1/4 and one 3/16. And a lot of times.....the ones with 2 keys are not dead on 180 apart. So...hence I just do 1 key.

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    Senior Member slotracer's Avatar
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    well thanks for the information as always its a great help to me when building these dam engines on my own. i will call the machine shop in the a.m. and have them check the hub to see what size it is and to tell him to do the 1/4" on it. just hope my hub is 1/4" or like every other time have to buy another one and add another part to the pile.
    slot
    87 eliminator
    next boat ??????????????
    new owner of the redneck yacht club
    Stockton, ca.

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    We can broach the balancer and key the crank. You can customize the broach to line up perfectly and an indexing head on the mill for the crank.

    Same indexing head we use to put a new bolt circle in wheels. Well not the same one, we have 3. The one for wheels has been modified a bit to accomodate wome wheels.

    Find the center of the existing key and rotate 180.

    Make a stepped key if you have a stock crank and aftermarket balancer 1/4 keyed.

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    Quote Originally Posted by slotracer View Post
    i bought a dc 8-71 blower and now am finally getting around to building the engine i brought the pulley to the shop to get everything balanced and there is only one keyway. so it sounds like i will be all right then. do i make the keyway 1/4" or is it that size already? its on a bbc
    If it's a blower hub...and one keyway....I am sure it is 1/4". You do know that there is a different "hub" that is sold for external balance...if you are using an external balance crank. The hub has a counterweight on it.
    I have a couple of them here if you need.

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    Yea if you have an external balance hub with a counterweight, and there are 2 1/4 keys. The counterweight on the hub lines up with the counterweight on the crank.

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    LOL. Yeah.

    One time I built a guy an external balance blown gas deal for a street rod. Was a year later before I happened to catch the guy at the Hot August night deal here.
    I asked him how the motor was doing and he said it was a little "too wild" so he and his buddy changed the camshaft to a hydraulic roller deal.
    So he fires it up and I notice a lot of "shakin goin on" in the fenders....especially for a blown deal.

    Sure enough....he put the external hub on 180 out. It ran a year that way.

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    Quote Originally Posted by Fiat48 View Post
    LOL. Yeah.

    One time I built a guy an external balance blown gas deal for a street rod. Was a year later before I happened to catch the guy at the Hot August night deal here.
    I asked him how the motor was doing and he said it was a little "too wild" so he and his buddy changed the camshaft to a hydraulic roller deal.
    So he fires it up and I notice a lot of "shakin goin on" in the fenders....especially for a blown deal.

    Sure enough....he put the external hub on 180 out. It ran a year that way.

    Boater would not have done that. LOL He should have just flipped his bearings and ran it for another year.

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    LOL.
    Yeah..this guy thought all was normal. Never had a clue. Thought the shakin was cool.
    So did the guy at the drags who ran an external balance flexplate on a 427. Wondered why his fenders were always missing bolts.

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