what kills rod bolts more?

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Baxter61 said:
For a given motor, what kills them more; rpm or hp? Discuss
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Cool thread Baxter..............Piston weight vs. rpm. HP really applies downward force where as rpm has to stop the piston at the top trying to stretch the bolts. So rpm, imo is the main factor.
 
Also when the other piston fires it jerks down on the rod so HP is also a devil in this game.My guess is all of it.
 
mopar410 said:
Also when the other piston fires it jerks down on the rod so HP is also a devil in this game.My guess is all of it.
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Yep..... And also what role does harmonics/balance play in the long term stress on the bolts?
 
The lighter the piston and rod would have less stress on the cap,which would turn rpm's quicker and would have less throw weight.So weight is another issue.
 
Gotta admit it's pretty amazing what a stock forged bottom end can take. My issues over the years were always valvetrain related....
 
I can answer that very simply without all the "harmonics" and "distortion" and all the high brow BS. Here we go. You ready? What absolutey kills the HELL outta rod bolts are dumbasses. Shall I explain? Allow me. Next time you're at the races.....or on the street and hear some FOOL sittin still in his car and repeatedly revvin the motor like this....WAAAAA.........WAAAAAA .......WAAAAAA........WAAAAAA THAT's what kills rod bolts. Plain and simple. Everytime an engine is free revved, the rod bolts stretch ever so slightly and the big end of the rod elongates and then goes back. That's why when people use used rod bolts, I always shake my head. I mean, 50-75 bucks and you couldda had good ones. So, what kills rod bolts?


DUMBASSES.


Here endeth the lesson. lol
 
StrokerScamp said:
I can answer that very simply without all the "harmonics" and "distortion" and all the high brow BS. Here we go. You ready? What absolutey kills the HELL outta rod bolts are dumbasses. Shall I explain? Allow me. Next time you're at the races.....or on the street and hear some FOOL sittin still in his car and repeatedly revvin the motor like this....WAAAAA.........WAAAAAA .......WAAAAAA........WAAAAAA THAT's what kills rod bolts. Plain and simple. Everytime an engine is free revved, the rod bolts stretch ever so slightly and the big end of the rod elongates and then goes back. That's why when people use used rod bolts, I always shake my head. I mean, 50-75 bucks and you couldda had good ones. So, what kills rod bolts?


DUMBASSES.


Here endeth the lesson. lol
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Hey Rob, so how does the motor go when some dumbass steps on the rev pedal?
 
voo--bah!!! VOOOOO---BAHHHHHH!!!! VOOOOOO--eefffin'kabooom!!!
 
Improper stretch is a big one. Heavy components is another. HP is really not much of a factor, especially compared to the above 2 reasons.
Then there's detonation which pounds the bearings hard and deforms the big end which stresses the bolts.
Brian
 
Expanding on Brian's post - Any bolt has a certain expected life, based on material, manufacture, and load. It's designed to work with a certain amount of life span given the expected load.In terms of a rod bolt, the worst things for it are "extra" harmonics and improper install/preloading. The free revving doesnt hurt anything as long as the engine is correctly done. If you think otherwise, go find the video of the Indy engine playing "We Are the Champions" by alternating rpms...lol. But, if the bolt is nicked during install, or the threads are not lubed with the right stuff, and it's not torqued to he preload the manufacturer designed in, then the lifespan has been reduced. How much depends on the amount of "wrong" and the usage. Harmonics kill and wound a lot of otherwise good engines.
 
if you keep hitting the rev limiter, that hurts parts. The rev limiter should be set high enough that you never hit it but there just in case of driveline breakage
 
moper said:
Expanding on Brian's post - Any bolt has a certain expected life, based on material, manufacture, and load. It's designed to work with a certain amount of life span given the expected load.In terms of a rod bolt, the worst things for it are "extra" harmonics and improper install/preloading. The free revving doesnt hurt anything as long as the engine is correctly done. If you think otherwise, go find the video of the Indy engine playing "We Are the Champions" by alternating rpms...lol. But, if the bolt is nicked during install, or the threads are not lubed with the right stuff, and it's not torqued to he preload the manufacturer designed in, then the lifespan has been reduced. How much depends on the amount of "wrong" and the usage. Harmonics kill and wound a lot of otherwise good engines.
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Yes, I have never seen an engine that I have put together come apart because of free revving! Now if the engine is HURT and you keep revving it up trying to find the problem, or just frustrated...because it's HURT...it will come apart! But that seems like commen sense!!
 
dodge freak said:
if you keep hitting the rev limiter, that hurts parts. The rev limiter should be set high enough that you never hit it but there just in case of driveline breakage
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No, it doesn't. MSD takes out cylinders by dropping spark. It's the same thing as a two step and guys sit on that all the time... Factory EFI takes it out by cutting fuel. Neither hurts the engine in the least assuming it's healthy.

But - without any load on it, there is little to stop an engine from exceeding it's safe rpm point - then things start to break. But that's from being an idiot and exceeding the redline, not that actual load-free rpms.
 
Hmmm, well why does rev limiters have a dirty name in racing ? Go on speedtalk, many of those engines builders swear rev limits hurt engines if they are used too often
 
I'd say RPM especially with heavy internals.
 
WAAAAA.........WAAAAAA .......WAAAAAA........WAAAAAA


lol
 
dodge freak said:
Hmmm, well why does rev limiters have a dirty name in racing ? Go on speedtalk, many of those engines builders swear rev limits hurt engines if they are used too often
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Everyone's got opinions. Mine's if it's for short times, an intermittant alternating miss (two step) is no problem and the rev limimter is perfectly safe when chipped properly for the engine it's minding. They do affect the engine, but in no way should they get near the failure threshold unless there was another problem. Any miss causes harmonics and places stress on things but if those are enough to break your engine you used the wrong parts for the application. Free-revving simply makes it very easy to exceed the engine's safe rev range.
 
dodge freak said:
Hmmm, well why does rev limiters have a dirty name in racing ? Go on speedtalk, many of those engines builders swear rev limits hurt engines if they are used too often
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Because the internet is full of idiots that know everything and have done nothing. Everybody wants to be a computer chair expert. Go to the drag strip and walk through the pits. You'll see real quick what works and what does not.
 
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