Butcher Crank

[tom n]

I'm building a new engine for my car and have been searching for info on SR's running a butcher crank. Doesn't seen like its used here like in the DSM world.
Anyone have any experience with one in a SR?
SR crank are crazy heavy


http://www.ffwdconnection.com/butchercrank.html

[Def]

I've seen that done before (aero profiling the counterweights) - it makes sense, but I guess it depends on the cost as to whether it's worth it. SR cranks are super heavy...

[Def]

BTW - wouldn't you need to balance things with the correct bob weights of your reciprocating components?

[tom n]

I believe it runs $550-600 and they balance it to .1 ounce/inch tolerance. Pretty sure that's better balance than factory.

People have been using them in the dsm world for 10+ years. DSM crank don't start out nearly as heavy. Surprises me I can't really find any info on them in SR world.

[Def]

How can you balance something with less than half the bits that rotate around? Yea, for one piston/rod going down, there's another going up, but a balance with bob weights will be different than one without.

[tom n]

Are you talking about balancing the crank or the whole assembly?

[tom n]

Cost is $680 with the Vader coating.

[Matt93SE]

as long as you balance the whole thing, have at it. not real sure it's worth the cost unless you're really reaching for that last 3hp..

[tom n]

It's not a V engine. As long as rods and pistons are weight matched I see no need to spin balance them with the crank.

Where do you come up with the 3hp gain number? I would think the benefits are more than just hp related. Was hoping there may be some here with actual experience with one in a SR.

[Def]

Why not just get a much lighter clutch/flywheel combo for cheaper? Way less inertia if that's what you're going for.

I'd be really surprised if the aero profiling makes more than a few HP difference. That's A LOT of aero drag on something as compact as a crank.

[Matt93SE]

Was hoping there may be some here with actual experience with one in a SR.

Good luck with that. On any forum. Way too many poseurs out there that talk a lot, and the smart ones stay quiet. With posts like this, you're likely not going to get much help.

[tom n]

Why not just get a much lighter clutch/flywheel combo for cheaper? Way less inertia if that's what you're going for.

I'd be really surprised if the aero profiling makes more than a few HP difference. That's A LOT of aero drag on something as compact as a crank.

Already have a lightened flywheel. Clutch is a Silk Road set up. Not sure the weight of it.

The benefits I would think are not just about HP gains. Being knife edged it would certainly not churn the oil up as much. It would slice right thought it.

Good luck with that. On any forum. Way too many poseurs out there that talk a lot, and the smart ones stay quiet. With posts like this, you're likely not going to get much help.

Sadly that's all to often true.

[Def]

I mean a really low inertia setup like a 7.25 or 5.5" clutch setup.

There will be a little less frothing of the oil, but I doubt it's that much.

Isn't this something you could do with a few hours of time on a die grinder and then get it balanced locally later?

[tom n]

What's a good 7.25 set up that's street friendly for a SR20?
And can handle 450-500 TQ.

[Matt93SE]

What's a good 7.25 set up that's street friendly for a SR20?
And can handle 450-500 TQ.

Street friendly and ultralight drivetrain are mutually exclusive.