Is it fact or fiction?
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Is it fact or fiction?

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    Junior Member Cap-n-Carl's Avatar
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    Default Is it fact or fiction?

    My late father was an old school mechanic. He always said that if you rev a V8 engine to four or five thousand rpm and held it there with no load, the engine would self-destruct in a short period of time. I have always had trouble raping my head around that one!
    I would think it would not matter as long as you don't over-speed the engine! Any opinions?

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    Default Time......?????

    Quote Originally Posted by Cap-n-Carl View Post
    My late father was an old school mechanic. He always said that if you rev a V8 engine to four or five thousand rpm and held it there with no load, the engine would self-destruct in a short period of time. I have always had trouble raping my head around that one!
    I would think it would not matter as long as you don't over-speed the engine! Any opinions?
    Time, a reasonable question... How long? And at 4 or 5K??? How old is the motor?..... I've seen factory stock, 100,000 mile, American V8s in old sedans that wouldn't blow up if you stuck a brick on the gas pedal..... Internal friction, and out of balance drag, would "govern" them to a rev limit that prevented self destruction..... I imagine there are examples of the opposite, but I'd have to say no to 4K for 3 minutes unloaded....5K might get a little iffy, depending on the overall condition of the engine in question.... Have you ever seen the video of the "break in" of a F1 engine????

    Ray
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    gn7
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    Ever seen a NHRA ProStock, or Top Alky car, or a ProMod stage. Scary



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    Quote Originally Posted by Moneypit View Post
    Time, a reasonable question... How long? And at 4 or 5K??? How old is the motor?..... I've seen factory stock, 100,000 mile, American V8s in old sedans that wouldn't blow up if you stuck a brick on the gas pedal..... Internal friction, and out of balance drag, would "govern" them to a rev limit that prevented self destruction..... I imagine there are examples of the opposite, but I'd have to say no to 4K for 3 minutes unloaded....5K might get a little iffy, depending on the overall condition of the engine in question.... Have you ever seen the video of the "break in" of a F1 engine????

    Ray
    Linkey please
    And what oil are they using?
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    Senior Member SHAWN DAVIS's Avatar
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    He is correct,
    after staging my outlaw pro mod at 6000, they hardly last four sesonds

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    Senior Member stix818's Avatar
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    Ray, F1 break in is crazy!!!!

    I say there's to many variables but I know that when I put heat into my motor at the races I hold it at one RPM rather than rapping the throttle a bunch until I get heat into it.. I usually hold it at around 4k RPM.. When I break in my race motor I also hold it at about 4k RPM.. Never have had any issues!!
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    Senior Member stix818's Avatar
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    Quote Originally Posted by gn7 View Post
    Ever seen a NHRA ProStock, or Top Alky car, or a ProMod stage. Scary
    Exactly Bob and that's well over 4-5k!! Except the IHRA guys, I guess they leave the line at or around 6500.. A lot more cubes though!!
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    Quote Originally Posted by gn7 View Post
    Ever seen a NHRA ProStock, or Top Alky car, or a ProMod stage. Scary
    Do You really think His Father meant a top alcohol car and not his Oldsmobile parked in the driveway?
    Last edited by Flyin-Bryan; 09-18-2012 at 03:13 PM.

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    gn7
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    Quote Originally Posted by HammerDown View Post
    Linkey please
    And what oil are they using?
    Not exactly breaking one in, but you get the idea.



    As for the oil Hammer, you need to now for which track! Think I'm joking? Look at what they do about fuel for each track
    LINK: F1 fuel blender



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    Last edited by gn7; 09-18-2012 at 03:31 PM.

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    Senior Member stix818's Avatar
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    That's interesting Bob.. Makes sense but didn't realize they have different blends.. I figured they just had a spec fuel similar to Comp E and Pro Stock..
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    gn7
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    Quote Originally Posted by stix818 View Post
    That's interesting Bob.. Makes sense but didn't realize they have different blends.. I figured they just had a spec fuel similar to Comp E and Pro Stock..
    Nah, they are more like your average everyday GN team. 3 different fuels used thru the year. Ooops, did I just say that? I meant 3 different suppliers, errr, 3 different brands, ahhh, I mean what ever is on sale

    The F1 boys run stuff that can hardly be refered to as gasoline.



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    Default Brick....

    Quote Originally Posted by Flyin-Bryan View Post
    Do You really think His Father meant a top alcohol car and not his Oldsmobile parked in the driveway?
    My brick comment was exactly that, an Oldsmobile..... I remember it was a 4 door, mid to late 50s. It was hit parked at the curb without any compressive coverage... The junk guy was a real dick, low balled the woman for a wreck that was cherry from the rear doors forward.... After he left, we did exactly that with the brick.... Sucker would not blow up, seemed to get to the valve float RPM and just back down a bit, then rev, and back down..... Couldn't blow it up....
    Ray
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    Can't re-Member 28Eliminator's Avatar
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    Pops forgot to take his early 90s Toyota Rav 4 out of gear one day after he hooked it up to the back of his 36 diesel pusher moho... Just imagine.... He said he got it up to about 50 before he noticed the smoke in the rear view mirror. Yep, it was in first gear

    We figured it had to have been turning around 7000 rpm's for about a minute.
    Rattled like a son of a bitch when he first fired it up, but it ran. That was 4 years ago, and it still runs... Has a small valve train tick, but runs fine.

    Pops use to tell stories about GM testing the first SBC 265's.... Many hours, no load, at high rpm's... Sometimes for days at a time...


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    Senior Member snoopjonnyjon's Avatar
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    I wonder if this legend started over someone getting the idea some engine had a natural frequency between 4000 and 5000rpm? I read a paper recently that showed a crankshaft from some V8 that had a natural frequency at 4600rpm, so there might have been some validity to it. Maybe there was some very early racing V8 that didn't have a crank damper that got the legend started? Or maybe just an urban legend based off someone with a little bit of knowledge.

    A few years ago, we had an issue with gearboxes breaking on a cornheader. The gearboxes were running two parallel shafts that fed corn stalks between them. They were the same gearboxes that had been used for years. Previously, the drive on the combines were just a straight 2 speed box, but the combine had recently been changed to a variable speed drive. In the middle of the variable speed range was the natural frequency of the gearbox. It was a very fine adjustment to make it do it, but if you got it just right, the thing would set off a terrible vibration, getting increasingly worse. Once excited, it would keep vibrating, even after the load was removed. Turning around at the end of the field, you could see the shafts vibrating enough to be contacting each other. It was like the Tacoma Narrows Bridge! Turning the speed up or down would make the vibration go away.

    I can't see it having any validity with even a semi-modern engine that has a damper though.

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