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View Full Version : Definitive ka24de crank pulley question


NashT
02-11-2020, 11:32 AM
Hey guys i recently picked up a full set of NST under drive pulleys for a steal.

Im only planning on running the crank and water pump not the alternator pulley.

Anyways ive been reading previous posts on here and on nicco, and am now skeptical about running the crank pulley.

Does anyone have any real experience with any negatives running an aluminum crank pulley?

I understand the ka's crank is only half ballanced, and the stock crank pulley has a dampner ring weight for vibrations, but im guessing its not actually a weight for the crank like on an old v8 with a harmonic ballancer.

Basically, if I run this NST crank will I run a risk of spinning a crank bearing?

And for the guys who would argue to only use the stock crank or ATI, what about when you change fly wheels to a light weight one, that in turn would change the ballance weight of the crank on the back side. (Just a comparison)

And no i dont care about the insignificant hp gain if any, i just couldnt pass up buying this NST set for 80 bucks.

So has anyone had any negative issues arise from running an aluminum crank pulley?

Thanks and sorry for the novel

S14rebuild
02-11-2020, 12:41 PM
Not a ka, but on an sr, ran an all aluminum crank pulley, no negative effects, put easily 15k on that motor..not 1 negative except for finding the proper size belts to run

NashT
02-11-2020, 06:31 PM
Basically in the mass of posts ive read its all been speculation without any proof running a solid crank pulley is bad for the bottom end.

The guys who are running solids say they have for years.

Those opposed to solids dont have any definitive proof, just that there 3rd cousins friend of a friend blew a motor that had a solid crank pulley.

I understand the dampening of vibration, but i just cant see it actually causing harm on a regularly driven KA opposed to say a full race built motor

mechanicalmoron
02-11-2020, 10:27 PM
I understand the dampening of vibration, but i just cant see it actually causing harm on a regularly driven KA opposed to say a full race built motor


You understand the reason, but think maybe if you did it regularly instead of just rarely, it would be totally fine.

Okay.

NashT
02-12-2020, 07:31 AM
You understand the reason, but think maybe if you did it regularly instead of just rarely, it would be totally fine.

Okay.

Its an internally ballanced motor, not an old domestic V8. So your point has zero merit as usual moron.

And I dont want this thread to turn into another 50/50 argument like all the other threads I have read. Trying to get an actual answer on this topic- and it seems the divide is equal.

Please only post if you have some credible real life expirence on a solid aluminum crank pulley

tuzzio
02-12-2020, 09:02 AM
No real life experience on my KA, and here is why.

A KA is only SEMI balanced from the factory. Which is why the STOCK damper pulley is important (IMO)

If you had the rotating assembly balanced with the pulley you plan to use, it would be a different story (IMO)

I spent the money on an ATI for my built KA, but thats just me.

NashT
02-13-2020, 01:47 PM
Thanks tuzzio

mechanicalmoron
02-13-2020, 05:58 PM
Its an internally ballanced motor, not an old domestic V8. So your point has zero merit as usual moron.

And I dont want this thread to turn into another 50/50 argument like all the other threads I have read. Trying to get an actual answer on this topic- and it seems the divide is equal.

Please only post if you have some credible real life expirence on a solid aluminum crank pulley

A KA is the 350 of silly little 4 bangers. You can say "old domestic v8" all you want, but tuzzio fixed that for you, and it's a harmonic damper, it's a matter of the rubber and how much is on which side of the rubber and all that. It's not the same as a damper with a big balance weight on one side, and it's not the same as a flywheel with a lot of mass everywhere. It's there to shake just right, to band-aid the lack of balance up to the top of the KA's power band.

If there was ever a little 4 banger that thought it was a big old domestic v8, it was the ka. That's why they're fun to drive.

NashT
02-13-2020, 06:32 PM
Obviously its not a harmonic ballancer, it is indeed just a dampner weight thats centripetal, unlike a harmonics weight.
-But this is not the question/ arguing point-

Reading every post i could find, again everyone opposed to running a solid crank was all just speculation, no definitive proof of it causing abnormal damage or wear.

A few ppl said its just to absorb the ac clutch, others said they saw not a single difference in wear when rebuilding engines that ran solids cranks.

Im not trying to argue with anyone, theres logic on both sides.

Im just simply wanting to know if anyone has a definitive answer with real expirence to back it up, not just speculations.

From every post i could find specifically pertaining to the KA, literally the ppl were divided on the matter. And for all those saying it destroys the bottom end there was no proof at all.
However there were quite a few ppl that said they had been running a solid for years with zero issues. (Yet anyone can make a false statement everytime)

Because I could find no post with actual validation either way, that is why I created this thread.

And guys I would just buy an ATI but im not going to run this KA to much longer, still trying to make my mind up on which swap. The only reason this shit came up is I ran across this set for dirt cheap and I figured what the hell.

TheRealSy90
02-14-2020, 05:43 PM
Shouldn't be spending any money on any KA parts if that's the case.

Kingtal0n
02-16-2020, 10:51 AM
think what you want but every engine I've ever seen with one of those aftermarket pulleys has wound up with a spun bearing. Could just be a coincidence but there are still garbage blocks laying around my friends shops with those things attached that keep reminding me.



Based on what I know about engineering it is entirely possible that the OEM pulley has more of a damping effect than most people realize. It's hard to imagine something like that having such a dramatic effect but better safe than sorry at this day and age. My recommendation is to use the OEM pulley on the OEM engine, otherwise if anythings been changed inside the motor use an ATI damper and call it a day.


Vibrations, harmonics, every machine has them, any device with a frequency associated (rpm is a frequency also known as angular velocity or angular speed often denoted as a 'w'), even an electronic oscillation, can be over damped, under damped, has a resonance, frequency response, 'bode' plot, and so forth. It's hard to 'see' without advanced computer modelling and simulation environment. Every material changes shape as it moves, endures force, stretches/shrinks elastically, and there is a whole lot of that going on inside an engine. Engineers are supposed to notice these things and take steps to dampen those dangerous frequencies and peaks when they threaten the livelihood of a device. Thing is, those counter measures aren't always obvious; sometimes its a little piece of rubber hanging off to the side that looks like a useless additional weight. Other times its in the mass and composition of a nondescript object.