what is a reasonable reliable rpm for 572 4.5 by 4.5

Old 05-13-2007, 08:54 PM
  #1  
badbug3
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Default what is a reasonable reliable rpm for 572 4.5 by 4.5

on a 572 bbc in a boat, what would be the top rpm to turn the motor to keep it reliable? It has 6.535 length rods and 4.5 stroke and 10.2 deck. I really need to add a little nitrous to get a little more power and need to turn 7000 rpm. Will the low rod stroke ratio take its toll at this rpm. This rpm is only obtained while running in a quarter mile and not for any length of time at all. Mainly on a drag run. Motor has ohio crank, and ohio i beam rods with arp 2000 rod bolts. Would it be wise to change the bolts to L-19 rod bolts? Compression is only 10-1.
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Old 05-14-2007, 06:40 AM
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billhendren
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7000 would be a piston speed of 5250,thats pushing it for the parts you have.I would replace the rod bolts with custom age 625 at least,there a far better bolt.Bill
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Old 05-14-2007, 06:44 AM
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topsportsman1
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572 with 6.535 in a 10.200 tall deck? Sounds to me son you got the wrong rods in this engine,because the math don't add up
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Old 05-14-2007, 06:55 AM
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4.5 stroke,6.535 length rods with a piston with a 1.415 compression height gives you zero deck.Why won't it work ?
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Old 05-14-2007, 07:02 AM
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topsportsman1
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It will work,but I'm not to accustomed to putting the pin that far down on the piston,my preference

I just believe it gets a better ring stack and better piston control with the pin hight closer to the top JMHO
Everyone does thing differently,I'd used the 6.7 rod or a custom aluminum
to get a better deck hight is all
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Old 05-14-2007, 07:28 AM
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I agree with you.I wouldn't use that short a rod in a 4.5 stroke but thats what he said he had.
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