12 wt crank

[dwg86]

I have an opportunity to get another 12 wt crank. What is a good(standard) grindable 12 wt crank worth?

[gradon]

I could get one from my local JY for $30, +$10 to tip the lift operator, so $40 plus my labor. There was a gremlin in there the other day with a 258. <$100 shipped for a good grindable used one and $200 for a ground one w/rod and main bearings included are reasonable prices. Then again, if you keep searching ads, you might find someone begging anyone to haul away a 258 block that's been sitting or ask $100 for the whole block(rods). . .

[dwg86]

I could get one from my local JY for $30, +$10 to tip the lift operator, so $40 plus my labor. There was a gremlin in there the other day with a 258. <$100 shipped for a good grindable used one and $200 for a ground one w/rod and main bearings included are reasonable prices. Then again, if you keep searching ads, you might find someone begging anyone to haul away a 258 block that's been sitting or ask $100 for the whole block(rods). . .

That sounds like a good price. Are you going to get it? I've been trying to get the 12 wt cranks, if it's a good price, to keep them from going to the crusher. It seams they are getting harder to come by.

[gradon]

I don't plan to get it, but I wouldn't mind having a spare 87-90 4-weight(or a 12-weight to trade for it) crank.

[Exos]

Got mine ground to .010 for 250$ CND with rod and mains.

[Gearhead88]

It seem's there are preferences with these crankshafts , I'd like to know why .

Opinions welcome , regarding why a twelve counterweight is prefered over a four counterweight or visa versa.


My 4.7 is a twelve counterweight , short rod (4.2) , I used the twelve counterweight / high inertia crankshaft . For me , it made sense that , when building an engine for torque and to be a used primarily at lower speeds, that the heavier crank would be best. I have a four counter weight crank too , it's a spare.


Some people prefer the lighter , four counter weight crank , I'd like to know why ?, I would assume , these would be more desirable for engines that will be reved higher or used over a wider range of rpm's , or , engines that have forced induction.

Is one crank known to be stronger than the other ?

[IH 392]

The only advantage (maybe?) that the 4 wt crank has is in acceleration.
And as for a good deal on a 12 wt crank?, I got all of mine, 4 of them, for hauling the cars off!, in fact the last one I got they threw the engine on the back of my truck when I wasn't looking!

[SilverXJ]

from what I have gathered the 12 wt crank is better is you have a manual transmission and if you operate a lot at low RPMs, simply because it has more inertia built up than the 4 wt crank. I also heard that the 12 wt is stronger.

I went with the 4 wt because I have an auto, so it wouldn't matter as much and because I couldn't find a decent 12 wt crank, but did find a nice .010/.010 crank.

[1bolt]

It is purely about inertia and windage... the 12cw will also have more frictional losses to oil in the crank case.

There's no reason to believe the 12cw would be stronger than the 4cw, in fact logic says the 4cw being lighter will be less stressed under rotation than a 12cw that weights much more. However there's no evidence for either case, I'm only speculating.

I wouldn't hesitate to use either crank in ANY application, even using a 12cw in a drag racing application... The heavier 12cw in a drag race might cost a little "accelerated horse power" (mostly when you rev up to launch RPM, so it would not be missed much) but it will store energy for the launch, so that when you drop the clutch or release the trans brake your engine has more inertia and doesn't bog as much when meeting the sudden friction of the flywheel or torque converter. Whether you'd lose enough time from lower accelerated hp after launch; to counter the gains in 60 foot times is open to debate. It would probably depend a lot on how heavy your car is.