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SCAT 258 crank weight

Posted: November 19th, 2017, 1:34 pm
by BcurpKodiak
Hi y'all!

Sorry if this has been posted before. I have seen approximate weights here and there, just not sure if I saw a definitive weight for the SCAT 258 crank.

I weighed it in my garage this morning. It's 48 lbs even.

Re: SCAT 258 crank weight

Posted: November 21st, 2017, 3:58 am
by Cheromaniac
Sounds right if it has four counterweights.

Re: SCAT 258 crank weight

Posted: November 21st, 2017, 8:52 am
by SkylinesSuck
How much does the 12 counterweight crank weigh?

Re: SCAT 258 crank weight

Posted: November 22nd, 2017, 7:46 am
by Cheromaniac
I weighed mine in at 66lb.

Re: SCAT 258 crank weight

Posted: November 22nd, 2017, 8:19 am
by SkylinesSuck
Thanks

Re: SCAT 258 crank weight

Posted: November 22nd, 2017, 2:13 pm
by Russ Pottenger
BcurpKodiak wrote:Hi y'all!

Sorry if this has been posted before. I have seen approximate weights here and there, just not sure if I saw a definitive weight for the SCAT 258 crank.

I weighed it in my garage this morning. It's 48 lbs even.
48lbs sounds about right.

I know in Scat's box it's 51lbs when I'm shipping

Re: SCAT 258 crank weight

Posted: November 22nd, 2017, 4:52 pm
by SkylinesSuck
I'm surprised there is such a difference in the weights. That must be a noticeable difference in how it revs up when you blip the throttle I assume?

Re: SCAT 258 crank weight

Posted: November 22nd, 2017, 11:13 pm
by IH 392
SkylinesSuck wrote:I'm surprised there is such a difference in the weights. That must be a noticeable difference in how it revs up when you blip the throttle I assume?
If you look at them side by side it's obvious why the 12 cw crank weighs more.
The acceleration difference isn't as great as it may seem, the "moment of inertia" is small, by cutting the inertia ring off of the front of the flywheel will get you faster acceleration than the weights of the crank, and the extra weight of the 12 cw crank also aids greatly in dampening the pulses so they are much smoother.
The only reason they removed the counterweights was to cut materials costs.

Re: SCAT 258 crank weight

Posted: November 23rd, 2017, 12:17 am
by Cheromaniac
IH 392 wrote: The acceleration difference isn't as great as it may seem, the "moment of inertia" is small
It's so small that the difference in acceleration is insignificant.

Re: SCAT 258 crank weight

Posted: November 23rd, 2017, 10:58 am
by DaemonForce
The difference between the 12cw and 4cw crank is a grand total of 18-20lbs depending on hardware. The whole point of building a 258 or stroker with the 12cw crank is to make a quiet jobber. These are AMC engines, not the IH 392/462/554. Nobody does that anymore. These engines are outfitted purely for vehicles and the added production weight is counter-productive to an already aggressively large blueprint. Use the 4cw crank and make sure everything is properly balanced. It will not only last but will be fun the whole time. :cheers:

Re: SCAT 258 crank weight

Posted: November 30th, 2017, 7:49 pm
by 6TIME
SkylinesSuck wrote:I'm surprised there is such a difference in the weights. That must be a noticeable difference in how it revs up when you blip the throttle I assume?
I've ran both the 4cw and 12cw in the same motor. I cannot discern a difference on rev speed with the heavy crank. The 12cw does run smoother above 3500rpms than the light one did and both cranks were balanced.. The heavy crank rocks the car pretty good upon revving though lol. I swapped out the 4cw crank in favor for the heavier one to try to help dampen harmonic vibes and it helped considerably in my setup.

Re: SCAT 258 crank weight

Posted: December 1st, 2017, 4:43 am
by SkylinesSuck
Great input, thanks.