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Knife-edged crank


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did anyone that had or talked about it with the machinist bring up the fact that our rods and pistons are not very light. I spoke with a local machinist and his concern was that if he takes too much weight off that it will be hard to balance with a heavy rod piston combo. I don't have an extra $700 to buy a set of the billet rods so I'm concerned that if I have weight taken out that I'll have to put heavy metal back in the crank to get it right. I just don't want to dump a bunch of money into this and be the guinea pig... at least not unless I feel its going to work 100%. :wink:
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Heefner~ I see what you are saying. I use to get knife-edgeing and v-cut confussed (meaning: What I thought was knife-edging was actually V-cut). I don’t think I’d risk going has where I have all ready because I think it gets to a point to where a motor is not all that streetable and will only right at high RPM’s
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Dog,

can you clarify that last statement a little? I'm not sure if you are for or against the light lighten crank hindsight.

 

As for weight, I weighed my stock crank today 38 lbs 12.5 oz. So it looks like you are just under a 10% savings in weight.

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Well you can always goo too light, the question is : who is the judge of how much that is? the answer is different for every setup, and for every driver.

 

I was told up and down, and even sideways when we tried to get the fidanza flywheels made ~5 years ago that I was crazy saying they are a good upgrade (I've ahd a 10 pound HKS flwheel for 12 years now). Many told me I was wrong, that haivng a 10 pound flywheel would ruin the motrs power curve, make it idle like a$$, and a slew of other bad things.

 

Well now it's a starndard item in most builds, and has been accepted, but with lots of "naw, that won't work". this crank modification is similar in many ways, it will free up power and increase engine responce for the same reasons the light flywheels did. Can you go to far? sure you can, soo light and it most deffinalty will idle like crap. but we're only talking aobut pulling ~8 pounds off a 38 pound crank, not 25 pounds like the fidanza vs. the stocker.

 

It can and probalby does reduce the lifespan of the mains, but for most concidering this modification, loosig 20K mile of engin life is OK, Like myself, I've only driven my car a few thousand in the last 10 years, I dont' care if I only get 30K out of this motor, at this rate I'll have the same setup for 100 years :P

 

Also, I have a place that will do billett aluminum rods for ~$580 (60% the weight of stock) and we know the forged steel ones can be gotten for ~$700. It would be better to change rods too as Heefner stated.

 

My thoughs,

 

>don't do it on a street only motor

 

>don't do it if you run a stock flywheel cause lightening that will do more good anyway

 

>don't do it if you are on a tight budget cause that money can be better spent in other areas

 

>only do it if you already have a lot of other stuff done and want to make the most of all of it.

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i only want to rebuild it once and i want to do it to the max the first time.

 

As of now i got

Act 2600 clutch

Fidanza flywheel

Weisco pistons .40 over

Dads rods

Stainless steel valves oversized

Marnel head ported and polished

 

I planned on going with a T3/T4 turbo setup

I Have most of the expensive items but still need quite a bit.Possible MPI in the future but that wont be until next 08

I plan on getting my crank vcut so that would still put it at at least a 30lb. crank

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Can you go to far? sure you can, soo light and it most deffinalty will idle like crap. but we're only talking aobut pulling ~8 pounds off a 38 pound crank, not 25 pounds like the fidanza vs. the stocker.

 

It can and probalby does reduce the lifespan of the mains, but for most concidering this modification, loosig 20K mile of engin life is OK, Like myself, I've only driven my car a few thousand in the last 10 years, I dont' care if I only get 30K out of this motor, at this rate I'll have the same setup for 100 years :P

.

 

I'm less concerned with idling issues and more with bearing wear. The lighter flywheel really doesn't have a safety issue or pose any threat to engine failure as a lightened crank. I think pulling 8lbs is way too much. 8 lbs is a lot of material. I expecting to see a gain from the aero and fluid dynamics rather than the lightening.

 

I do agree that its a decision you will have to make, is the juice worth the squeeze in other words. If I was going for an all out race motor I think I'd go with the billet rods and take as much as possible off the crank but in my position now, I'll try to shave a few pounds off , make it look pretty and put it back together.

 

Thanks for the input Chad.

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this is only what is says on the website and in the magazine.Its common sense that they could take more weight off a 6 cylinder crank ect ect.,so maybe thats the weight you could take off with thos but with ours it could be less.I would call for some more accurate info
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Dog,

can you clarify that last statement a little? I'm not sure if you are for or against the light lighten crank hindsight.

 

I'm sorry, my mind shifted into N in the middle of typing that post. My wife called me, and you know how that goes 8).

 

I am defiantly for lighten up a crank. When I decide to build another motor. I'll lighten up that crank too. It's the V-cut that I'm not so sure about for a street motor. I'd have to see and feel the results before I went that far with it.

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  • 1 month later...
Update: I am having trouble keeping traction. The car wants to drive trhough the tires leaving the line. And when it gets to 20 psi, they are smoking again. That's in 1st and 2nd mostly, I ahve usually let off and started cruising when I get to 3rd. Given the way the motor revs, it does not take long to get to 20 psi.
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Sometimes old tires = hard rubber less traction it depends on the age and tire compound. Either way, I gave up trying to get someone to do mine so I'm doing it my self. I'm using an angle grinder and its a long process. Like polishing wheels by hand. You get the idea. I'm not shooting for a net savings of 5 lbs but just better aerodynamics than a rectangle. I may save a pound or 2 I'll post some pics if I think about it.

Let us know how the castilo crank comes out.

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  • 2 weeks later...
  • 4 weeks later...

Wow castillos is slow.

they had my crank about december 18th or so.I called him today and he said its ready to be heat treated and he should be done with that on monday and all thats left is polishing and balancing.

 

He said about 2 1/2 -3 pounds has been taken off with knifeedging and i asked about v cutting and he said that he would leave it the way it is.

 

Ill post pics when i get it.My guess it about a month with the way they move

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