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Old 01-12-2009, 02:44 PM   #1
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Default My old crank is cracked, what to do now?? Help!!

Should I knife cut/V cut the new one??

The old one was knife cut, but not the new style knife and V cut..

It will run me about $500 and will shave anywhere from 5-10lbs from the crank..

Pos and Neg..... Please tell me your thoughts.
Lets say $$ isnt a factor, even though it is LOL!!

Thanks everyone
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Old 01-12-2009, 02:50 PM   #2
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If money is a factor at all, I wouldn't knife cut it. Very little gain for the money. Spend that money elsewhere IMO. IE-spring for a lighter set of connecting rods, as this is 1000x more important as far as bottom end durability goes. Or lighter pistons; same idea. Plenty of better ways to spend 500 bucks IMO.
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Old 01-12-2009, 02:54 PM   #3
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I already have JE pistons and eagle rods.

I will have good bearings and ARP hardware.

I also plan to get lighter valves and better springs.

I have the volvo springs. What do you think of those??

I will also have the bowls blended and any cast marks removes.

A small amount of unshrouding too. There doesnt seem to be much need for that on this head.

Thanks Pat.

What about the advantages though??
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Old 01-12-2009, 03:08 PM   #4
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Quote:
Originally Posted by TURNS101 View Post
I already have JE pistons and eagle rods.

I will have good bearings and ARP hardware.

I also plan to get lighter valves and better springs.

I have the volvo springs. What do you think of those??

I will also have the bowls blended and any cast marks removes.

A small amount of unshrouding too. There doesnt seem to be much need for that on this head.

Thanks Pat.

What about the advantages though??
Eagle rods are heavy. About like stock IIRC. FM sells some fancy ones that are like 1K, but considerably lighter. If you're looking for high RPM longevity, light rods and pistons IS BY FAR THE BEST THING YOU COULD DO TO THE ENGINE!

Thing is, the crank just spins. Granted the weights and all aren't perfectly offset off the rod end, but it's proven that the minimal load the crank produces from spinning is negligible. What matters is the reciprocating weight attached to the crank. That's where huge loads come into play. Forces grow exponentially as RPM's go up. F=1/2*m*V^2. So as the speed goes up, forces skyrocket.

And from these loads, stems many problems. Crank flex, bearings spinning, vibration, etc. If anything, taking weight off the crank is gonna make it weaker. I wouldn't do it.
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Old 01-12-2009, 03:15 PM   #5
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Hmmm, makes sense..
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Old 01-12-2009, 03:38 PM   #6
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I would also agree. I cant wait to start on my next engine, which will be fun since it wont actually be my daily driver engine, so it wont be rushed. Ive never seen the point in a lightened crank outside of the most extreme race cars.

Also, how did the old crank get cracked? Could it have been the material removed? Did it let go because of crank failure, or did it get damaged after the fact?
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Old 01-12-2009, 03:58 PM   #7
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i have a knifed crank...it spins up like a ferrari.


well, maybe not, but you know what I mean.
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Old 01-12-2009, 04:01 PM   #8
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Quote:
Originally Posted by NA6C-Guy View Post
I would also agree. I cant wait to start on my next engine, which will be fun since it wont actually be my daily driver engine, so it wont be rushed. Ive never seen the point in a lightened crank outside of the most extreme race cars.

Also, how did the old crank get cracked? Could it have been the material removed? Did it let go because of crank failure, or did it get damaged after the fact?
I believe after the fact of the rod bolt breaking.

You can see it if you search 2 holes, and 2 holes part 2 in the BS section
It has the pics from the damage.
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Old 01-12-2009, 04:02 PM   #9
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Quote:
Originally Posted by hustler View Post
i have a knifed crank...it spins up like a ferrari.


well, maybe not, but you know what I mean.
See, I love that responce along with the light flywheel. Its awesome...
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