Cast crank in a four bolt block ?
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Cast crank in a four bolt block ?

  1. #1
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    Default Cast crank in a four bolt block ?

    My question is what horse power and RPMs can a cast crank safely handle in a BBC 454 four bolt main block?
    I'm planning a 92 octane friendly compression , (2) 750 cfms on a tunnel ram, rect. port 990 heads, hyd or flat tappet cam in a v-drive. 5800 rpm max in a v-drive boat. Is a cast crank in a four bolt safe to 6000 rpms? Thanks for any info.
    Last edited by zombie; 10-01-2010 at 08:36 PM.

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    gn7
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    You probably won't break it. But who's cast crank are you talking about? Just so you know, the four bolt isn't helping your crank live. You keep mentioning it like it makes a difference. It doesn't



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    Quote Originally Posted by zombie View Post
    My question is what horse power and RPMs can a cast crank safely handle in a BBC 454 four bolt main block?
    I'm planning a 92 octane friendly compression , (2) 750 cfms on a tunnel ram, rect. port 990 heads, hyd or flat tappet cam in a v-drive. 5800 rpm max in a v-drive boat. Is a cast crank in a four bolt safe to 6000 rpms? Thanks for any info.
    Is there a reason you don't just find and buy a good used GM steel crank, since you seem to have some other good parts? Shouldn't cost much in today's economy.

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    It is a Chev cast crank. So the four bolt mains do not do anything for a cast crank shaft? I do not think my motor will be running above 6000. So as long as that rpm on occasions is safe I'm good with the cast crank.
    right? Since I already have this set up in a motor I just got I'm trying to keep costs down.
    Last edited by zombie; 10-01-2010 at 09:04 PM.

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    gn7
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    The 4 bolts does zero. Like Obnoxious said, you would be better off with a steel crank. Even if it was in a 2 bolt block. But you have what you have. You will probably never hurt the crank. But you are wasting a perfectly good 4 bolt block



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    Last edited by gn7; 10-01-2010 at 09:48 PM.

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    Default yep

    Quote Originally Posted by gn7 View Post
    You probably won't break it. But who's cast crank are you talking about? Just so you know, the four bolt isn't helping your crank live. You keep mentioning it like it makes a difference. It doesn't
    im with you on this , 4 bolt block not going to make crank live longer with this type of build , cast cranks ive ran successfully all day long at around 500 hp and under 6500 rpm's and no problems , probably wouldnt push more than that but the biggest thing is to let oil temp get up before beating on it. ive seen more spun bearings because off the trailer and bam full throttle then wonder what just happened. like obnoxious001 said , forge be better.
    Last edited by Blown$um; 10-02-2010 at 04:08 AM.
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    Senior Member CK7684's Avatar
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    I'm running a cast crank without any issues...although around here my build is pretty mild

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    I'm No Expert Shaun's Avatar
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    My last motor was a GM cast crank making around 500 HP and turning around 5600 RPM. I beat the crap out of that motor. From what i was told RPM is what really kills these and that it's important not to spin them much faster than 6K.

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    My 18" Flat Hondo has 15% gears, 11 1/2" x 15" two blade. I'm feeling my motor will probably not exceed 6000 rpms. BTW Con. rods have 3/8 stock bolts. Probably go with stronger ARP bolts there. Thanks for the input. If I stumble across a steel crank I will probably buy just it to feel good about everything in the motor.

  12. #10
    just a ski boat with bark Carnivalride's Avatar
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    Quote Originally Posted by zombie View Post
    My question is what horse power and RPMs can a cast crank safely handle in a BBC 454 four bolt main block?
    I'm planning a 92 octane friendly compression , (2) 750 cfms on a tunnel ram, rect. port 990 heads, hyd or flat tappet cam in a v-drive. 5800 rpm max in a v-drive boat. Is a cast crank in a four bolt safe to 6000 rpms? Thanks for any info.
    Well I'm probably going to get a lot of crap for this but in my experience if a good GM cast crank is turned .010"/.010" with nice radiuses they will live well beyond 6000rpm.

    IMO, detonation is the #1 killer of cranks, then if you load and unload the prop that stresses the crank as well. With good machine work and some care in use and warming up before running hard they are better than most people give them credit for.
    Quote Originally Posted by gn7 View Post
    Carnivalride, you really need to find some other hobby. You have no talent for this boat thing

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    Senior Member grayson's Avatar
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    Quote Originally Posted by Carnivalride View Post
    Well I'm probably going to get a lot of crap for this but in my experience if a good GM cast crank is turned .010"/.010" with nice radiuses they will live well beyond 6000rpm.

    IMO, detonation is the #1 killer of cranks, then if you load and unload the prop that stresses the crank as well. With good machine work and some care in use and warming up before running hard they are better than most people give them credit for.
    I was starting to sweat on my set up, feel better now!

  14. #12
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    I ran a cast crank in a jet turning 5800 for years. If I remember right, it was turned .020/.020. I polished the beams of the stock rods and installed ARP bolts. It made about 500 HP. Raced it 1 year in a hydro turning 6800. Never had a problem with it.

    Tim
    Last edited by River Rat 005; 10-02-2010 at 08:10 PM.

  15. #13
    just a ski boat with bark Carnivalride's Avatar
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    Quote Originally Posted by zombie View Post
    My 18" Flat Hondo has 15% gears, 11 1/2" x 15" two blade. I'm feeling my motor will probably not exceed 6000 rpms. BTW Con. rods have 3/8 stock bolts. Probably go with stronger ARP bolts there. Thanks for the input. If I stumble across a steel crank I will probably buy just it to feel good about everything in the motor.
    Is this a true flat or a runner bottom?
    Quote Originally Posted by gn7 View Post
    Carnivalride, you really need to find some other hobby. You have no talent for this boat thing

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    Quote Originally Posted by Carnivalride View Post
    Is this a true flat or a runner bottom?

    It is a 1973 true flat .

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