ka crank

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rodrigo240
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ka crank

Post by rodrigo240 »

I got my la crank knifed and balanced is that a good thing or a bad thing because I heard the crank is not fully counter weighed
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motoman399
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Post by motoman399 »

that is a good thing. can you post pics of the knife edge?
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Post by rodrigo240 »

I can't get any pics the crank is already in sorry man
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TinyT
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Post by TinyT »

you ask if its bad after its done and installed? strange thinking. did you have the full rotating assembly balanced?
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rodrigo240
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Post by rodrigo240 »

Yes the rotating assembly was balanced
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Post by supakat »

more or less i am wondering why you are asking...cuz you dont just wake up and say i want my crank knife edged without knowing what it will do...that is like buying a whole set of parts without accurately determining your power goal/characteristics of driving...ie. making sure the cams complement the compressor map or build for drift or drag or street, etc...

did the machinist ask you to do it or did you read it in a mag...how much did he charge cuz i know a shop he that will do it and it is around $800 for the knife and $150 for balancing...
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rodrigo240
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Post by rodrigo240 »

I paid 500 for knifing and balancing my rotating assembly
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Post by rodrigo240 »

I knifed it because a friend told me my engine will rev faster I don't know much about ka's.
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Post by itwillboost »

rodrigo240 wrote:I knifed it because a friend told me my engine will rev faster I don't know much about ka's.
Lol well it is nice, it will allow you to raise your redline with a tune. Have your crank balanced is a good call.
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motoman399
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Post by motoman399 »

im really upset you didnt get pics of this 500 dollar job. i have never seen a knife edged crank before and was wanting to see how its done. oh well lol.
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TinyT
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Post by TinyT »

rodrigo240 wrote:I knifed it because a friend told me my engine will rev faster I don't know much about ka's.
did he also tell you your gonna need quality internals and a built head?
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Post by smbonn2005 »

And even still, with the KA half-counterweighted crank i wouldn't rev too much past 7300 or so. After the harmonics start getting pretty bad and motors get destroyed.
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Post by rodrigo240 »

Yea I have cp pistons 9.1 and eagle rods cometic head gasket.and my head has brian crower oversised valves and stage 2 cams plus brian crower springs and retainers
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Post by supakat »

smbonn2005 wrote:And even still, with the KA half-counterweighted crank i wouldn't rev too much past 7300 or so. After the harmonics start getting pretty bad and motors get destroyed.
The stock crank breaks at 10k...so reving to 8500 with a balanced/knife edged crank will be fine granted the valve assembly is done as well...with the bucket and shim design you can achieve this but valve float may happen with the stock springs...
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Post by smbonn2005 »

supakat wrote:
smbonn2005 wrote:And even still, with the KA half-counterweighted crank i wouldn't rev too much past 7300 or so. After the harmonics start getting pretty bad and motors get destroyed.
The stock crank breaks at 10k...so reving to 8500 with a balanced/knife edged crank will be fine granted the valve assembly is done as well...with the bucket and shim design you can achieve this but valve float may happen with the stock springs...
Correct you can, but the harmonics become bad enough that it starts to kill bearings quickly. I dont remember what series of racing it was but they had done research into it for their KA powered trucks and it resulted in anything over approx 7300 rpm the harmonics from having a half counterweighted crank would end up destroying the motor fairly quickly.
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Post by supakat »

correct as well but this leads to a experiment...run a knife edged half counter weighted crank with a red line at 8000 and see how long it lasts...if results show that you can run like this for at least two years, the pro's may weigh out the cons...i personally do not have money to buy a custom crank but if i were to buy a full counter weighted crank, i'd get the bc stroker kit...comes out to be cheaper than buying a crank separately then rods and pistons...just 3k is more than i have ever put into my car...let along 1k...
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Post by TinyT »

supakat wrote:
smbonn2005 wrote:And even still, with the KA half-counterweighted crank i wouldn't rev too much past 7300 or so. After the harmonics start getting pretty bad and motors get destroyed.
The stock crank breaks at 10k...so reving to 8500 with a balanced/knife edged crank will be fine granted the valve assembly is done as well...with the bucket and shim design you can achieve this but valve float may happen with the stock springs...
have you personally broken one at 10k?
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Post by supakat »

nope...information courtesy of import dps...

3. The stock 4 counterweight crankshaft can spin 11000 RPMS when only used for short periods of time. This is the biggest downfall in the KA, but keep in mind the engine was designed to make torque, not go rev happy.

I thought I read where they snapped the crank at 10k but i cannot find the thread...
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Post by rodrigo240 »

Thanks for the help guys I think im going to stop my build and buy a bc crank because I want my ka to be reliable
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TinyT
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Post by TinyT »

rodrigo240 wrote:Thanks for the help guys I think im going to stop my build and buy a bc crank because I want my ka to be reliable
um what? there are hundreds of reliable KA's with power you could only dream of and they dont have a fully counterweighted crank. i dont think you really know what you want, id do some browsing of other setups.
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rodrigo240
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Post by rodrigo240 »

So what do u think will b more reliable a stock ka crank or a knifed ka crank
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Post by TinyT »

rodrigo240 wrote:So what do u think will b more reliable a stock ka crank or a knifed ka crank
dude, that is not a factor in reliability. if you spin your motor to a reasonable rpm, say 8000, you will not have issues with a factory or knife edged crank.
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rodrigo240
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Post by rodrigo240 »

Thanks for the help
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TinyT
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Post by TinyT »

whats your plan for the rest of the setup
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motoman399
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Post by motoman399 »

i dont think the knifing has anything to do with how reliable its going to be for under 8000 rpm.

if i remember correctly, Ivan made over 1000 HP on a stock crank..
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Post by rodrigo240 »

Cp pistons 9.1 eagle rods cometic head gasket.and for the head brian crower stage 2 cams,bc oversised valves,bc springs and retainers,and my turbo turbonetics t3t4 with a peakboost turbo manifold I also bought the xcessive intake manifold that im going to run with a q45 throttle body and for my tuning I still don't know what im going to use
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Post by motoman399 »

what power are you looking for?
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Post by TinyT »

motoman399 wrote:i dont think the knifing has anything to do with how reliable its going to be for under 8000 rpm.

if i remember correctly, Ivan made over 1000 HP on a stock crank..
i dont think you remember correctly haha, ivan made 718whp. im sure they made more but not 1000

he was on a stock crank, nitride coated and shotpeened.

sidenote, i talked to him at sema last year and he still has the car and wanted to get down to 8.50's with it but i havent seen anything since on it.
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Post by rodrigo240 »

I want my motor to have like 380hp
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Post by Jmcc »

rodrigo240 wrote:I want my motor to have like 380hp

thats a large amount of money just for 380hp. :lol:

but you will have a lot more room for more power down the road.
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