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Safe racing RPMs

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Old 10-17-2007, 12:52 AM
  #1  
BatMobile00
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Default Safe racing RPMs

I was just curious how many RPM it is safe to turn on stock internals in our 4.6s. I am going to have my heads professionally done but chances are they are going to want 8,000 rpms to get max power. I need to give an RPM limit to base the port and valve designs on... Cams and springs will be done so that wont be the problem, just the internals.
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Old 10-17-2007, 01:22 AM
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racer02GTstang
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Default RE: Safe racing RPMs

i use to spin em at 6500 but people say dont go over 6200
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Old 10-17-2007, 01:31 AM
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ninelives19821
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Default RE: Safe racing RPMs

After the research i put into my engine build (talking to machine shops, reading, ext.) I would not run the stock rods of a stock 4.6 2v above 6000k rpms. I'm sure it can hang with it above that for a little bit but if you put alot of time/money in head work and some hot street/strip cams your motor is going to want to see alot of time in the red line for it to make the power it's supposed to. I'm running stage 2 comp cams with stage 2 heads and it peaks out at 6700 rpms.. sooooo yeah im pretty glad i got forged rods and pistons. As far as the the stock crank i have no idea what rpms it can hang to, but my engine builder said it can hang till about 600hp. If your budget can handle it try and get forged rods and pistons so you can run high rpms without worries.
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Old 10-17-2007, 07:24 AM
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bullittracr
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Default RE: Safe racing RPMs

well let me ask you this where did you get your forged pistons and rods, how much where they and on top of that how much was the install by the mechanic thanks. cuz i want to kenne bell the bullitt sometime and would feel alot better to do the bottom end.
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Old 10-17-2007, 05:54 PM
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bullittracr
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Default RE: Safe racing RPMs

sorry for being off topic
and steeling the thread bro
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Old 10-18-2007, 01:05 AM
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BatMobile00
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Default RE: Safe racing RPMs

aight looks like some rods and pistons are gonna be worth it... thanks guys
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Old 10-18-2007, 01:24 AM
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racer02GTstang
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Default RE: Safe racing RPMs

from what i have seen... its the crank that limits the rpms... lets say... a 99-01 cobra... it has the same pistons and rods to my knowlege. but its the crank that is different. it is forged. and those motors rev to 7k rpms. so i will say that the stock crank shouldnt rev very high. could have something to do with the balancing and such too.
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Old 10-18-2007, 01:26 AM
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racer02GTstang
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Default RE: Safe racing RPMs

oh.. my new shortblock with forged everything is good for 8000rpms... i just would never take it there, that is too high of rpm for any motor i would say, except like a honda. lol. i am going to limit mine to 7500rpms to be on the safe side.
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Old 10-18-2007, 01:42 AM
  #9  
ninelives19821
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Default RE: Safe racing RPMs

ORIGINAL: bullittracr

well let me ask you this where did you get your forged pistons and rods, how much where they and on top of that how much was the install by the mechanic thanks. cuz i want to kenne bell the bullitt sometime and would feel alot better to do the bottom end.
The rods and pistons were about $1100. As far as the labor for just installing that and nothing else i would think about $1000 bucks.
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Old 10-18-2007, 01:44 AM
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ninelives19821
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Default RE: Safe racing RPMs

Oh and they are Manley rod ands pistons. I think he got them directly from them.
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