3SX or other non-OEM Custom Crank Pulley vibrations vs STOCK CRANK PULLEY smooth ???

So what is the verdict?

Stay with OEM crank pulley or buy a solid crank pulley?

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Originally Posted by n2nsanity

Wow, little too much info here. I have a generic udp (got from someone else for cheap) and I'd swear it is somehow causing my belt and other pulleys to chirp and squeal. Before reading this last page, I was already planning on testing with the oem pulley back on to see if that helped. Now, I'm just going put the oem back on and leave it.

BaadVR4, just out of curiousity, what's this about aftermarket dampers? Don't believe I've seen or heard of them before.

Also, when you have a block from one car, heads from another, and crank from another, which pulley should you use? The one that matches the crank? Is any oem pulley enough? Do you need a custom damper at this point?

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torsional vibration is a function of a reciprocating engine. since the crank is the mechanical device by which reciprocating motion is transferred into rotational motion, it alone bears the stresses of said vibrations.

you design a damper to account for a variety of factors that determine resonate frequency of the crank. Number of cylinders, stroke length, cylinder configuration, desired RPM band, etc. AM dampened pulleys certainly exist--but the demand has never really justified building for the 3/s community (though there is at least 1 that i'm aware of). even a sub-optimal damper will provide some absorption under any circumstances; a solid pulley will not.

what is the verdict, steven? ray p. already spelled out his thoughts on the matter, based on his personal experience with a solid pulley. you can search for his threads if you want the info.

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Originally Posted by i3igpete

in my field of work (crankshaft and camshaft dynamics analysis) its not even a question of whether to use one. I can personally say I've designed dampers on everything from indian 1 cylinder scooters, to earnhardt-childress racing engines, to cummins locomotive diesels, to wartsila monsters. As in, I have the models, the test cell crank twist data, and a few prototypes on my desk.

but armchair experts will be just that.

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^^^^THIS.


This should be your verdict.

What happens when we run out of old OEM pulleys? I assume you're all going to be in line for the $1k aftermarket pulley?

personally, I would like to see a solid heavyweight steel pulley. Kills the issue of rubber reliability, with some of the benefits of a properly tuned damper. when it comes to non-viscoelastic pulleys, bigger is always better.

There are some references in this thread (about page 8 or 9, iirc) about Ross (an Australian company) and ATI having made dampers for the 6G72/4/5 engines. They are pricey, but probably the best answer if you don't want to trust the OEM damper or have lighter components/higher power output/aftermarket ECU/etc/etc/etc.

OEM dampers are designed to work with stock parts in a stock environment and controlled by stock ECU/etc. I suspect i3igpete would be a better source to answer your question, though.

Quote:

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Originally Posted by n2nsanity

Wow, little too much info here. I have a generic udp (got from someone else for cheap) and I'd swear it is somehow causing my belt and other pulleys to chirp and squeal. Before reading this last page, I was already planning on testing with the oem pulley back on to see if that helped. Now, I'm just going put the oem back on and leave it.

BaadVR4, just out of curiousity, what's this about aftermarket dampers? Don't believe I've seen or heard of them before.

Also, when you have a block from one car, heads from another, and crank from another, which pulley should you use? The one that matches the crank? Is any oem pulley enough? Do you need a custom damper at this point?

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Nah, some of us will be looking for the $ to fix the carnage from our first shattered crankshaft. And another solid pulley. LOL.

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Originally Posted by mb3000

What happens when we run out of old OEM pulleys? I assume you're all going to be in line for the $1k aftermarket pulley?

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Quote:

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Originally Posted by BaadVR4

Nah, some of us will be looking for the $ to fix the carnage from our first shattered crankshaft. And another solid pulley. LOL.

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Thanks for the personal insults. Keep 'em coming buddy.

Hey Pete, in your professional experience I must ask, what happens to the node when you cut the weight of the stock flywheel in half? Say it's at 200hz at 6000rpm. Will the predictable node move up, or down, in the rpm range when you reduce the flywheel mass? Conversely, which way does it travel when you increase the the weight?

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Originally Posted by mb3000

Thanks for the personal insults. Keep 'em coming buddy.

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if you think that's personal, you need to check yourself. besides...milt has more experience in hot-rodding than half this board combined, i'd wager.