Light 258 Crank?

FUNKYTEE5 · Feb 3, 2005

Just wondering if anyone out there has any more input on using the light 258 crank for a stroker? Other than not having the extra inertia at low rpm's and crawling, is there any other things to know about? Thanks

FUNKYTEE5

old_man · Feb 3, 2005

A good source of info is the yahoo strokers list.

Mike@Accurate · Feb 4, 2005

First, the inertia myth is just that. The mass on a crank counterweight is very close to the centerline. Not very effective as a flywheel. A few ounces at 8" out from center is like a pound near the CL. You would be hard pressed to notice a heavy crank from the seat of the pants. And, I tested a light (late) crank and stock 4.0 (544) rods (stock bolts) to over 440ft lb on the dyno. Nothing failed. And that was at 10.5:1 & 13# of boost. Don't sweat it. The whole issue is way overblown on the boards. Use the crank you have, the light (late) cranks "drop-in". MIKE

MrShoeBoy · Feb 4, 2005

Mike@Accurate said:
First, the inertia myth is just that. The mass on a crank counterweight is very close to the centerline. Not very effective as a flywheel. A few ounces at 8" out from center is like a pound near the CL. You would be hard pressed to notice a heavy crank from the seat of the pants. And, I tested a light (late) crank and stock 4.0 (544) rods (stock bolts) to over 440ft lb on the dyno. Nothing failed. And that was at 10.5:1 & 13# of boost. Don't sweat it. The whole issue is way overblown on the boards. Use the crank you have, the light (late) cranks "drop-in". MIKE

Are thoes dyno numbers from an engine dyno or a chassis dyno? And how did you manage 13 psi on a motor with a 10.5 CR ratio?

Then another question relating to crank weight: Have you noticed with a ligher crank that it pulls faster through the RPMs when compared to the heaver cranks because of the less inertia?

Thanks,

AARON

Mike@Accurate · Feb 4, 2005

As I said, the inertia thing is mythical. The difference between a light and heavy crank would be barely discernable. Either way. We have an engine dyno. We were looking for the limits of 4.0 stuff. Our shop truck is bored .125" (daily driven 80Kmi, so much for the ".060" is too much" myth). We put the smallest pulley we had on a 9:1 motor. When 13# of boost didn't hurt anything, we started taking cuts off the head and running more and more compression. At .090" off the head, we were at 10.5:1 (so much for the "don't cut too much off your Jeep head" thing). The motor was detonating and ran like crap (essentially undriveable without considerable tuning) but it made power. The "light" crank, stock rods & bolts, no main girdle and used-10-times head gasket all held up. I am putting the "old mule" engine in my own brother's truck. So many issues are blown out of proportion by web wheelers, I say "Let 'er eat" . MIKE

FUNKYTEE5 · Feb 4, 2005

Mike@Accurate said:
As I said, the inertia thing is mythical. The difference between a light and heavy crank would be barely discernable. Either way. We have an engine dyno. We were looking for the limits of 4.0 stuff. Our shop truck is bored .125" (daily driven 80Kmi, so much for the ".060" is too much" myth). We put the smallest pulley we had on a 9:1 motor. When 13# of boost didn't hurt anything, we started taking cuts off the head and running more and more compression. At .090" off the head, we were at 10.5:1 (so much for the "don't cut too much off your Jeep head" thing). The motor was detonating and ran like crap (essentially undriveable without considerable tuning) but it made power. The "light" crank, stock rods & bolts, no main girdle and used-10-times head gasket all held up. I am putting the "old mule" engine in my own brother's truck. So many issues are blown out of proportion by web wheelers, I say "Let 'er eat" . MIKE

Yup for sure! I just wanted some solid facts to base my build. I know that there are alot of myths out there! I'm just trying to sort them out with this inline six stuff! I'm used to V-8's. Anyways, Thanks for the input Mike

FUNKYTEE5

Dr. Dyno · Feb 4, 2005

Mike@Accurate said:
As I said, the inertia thing is mythical. The difference between a light and heavy crank would be barely discernable.

That's good to know. The lightweight 258 crank does save 20lb over the heavyweight 258 crank so that's less weight over the front wheels. That 20lb saving is also a money saver when it comes to shipping the crank to your home from the vendor.

Light 258 Crank?

FUNKYTEE5

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old_man

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Mike@Accurate

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MrShoeBoy

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Mike@Accurate

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FUNKYTEE5

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Dr. Dyno

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