# destroked ka idea.



## SVP5TEN (Apr 27, 2004)

i was just brain storming one day. but correct me if im wrong. i was thinking about how f1 cars dont have much torque but can get the rpms spun up pretty high. about the same thing as a bike. rod ratios going from 2.0 and up. im pretty sure some one has thought about it. but what if one were to drop an 86mm stroke with a custom long rod of 176mm. giving a rod stroke ratio of 2.05. if my math serves me right. just wanna know everyones .02 cents on this.thanks.


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## morepower2 (Apr 19, 2002)

SVP5TEN said:


> i was just brain storming one day. but correct me if im wrong. i was thinking about how f1 cars dont have much torque but can get the rpms spun up pretty high. about the same thing as a bike. rod ratios going from 2.0 and up. im pretty sure some one has thought about it. but what if one were to drop an 86mm stroke with a custom long rod of 176mm. giving a rod stroke ratio of 2.05. if my math serves me right. just wanna know everyones .02 cents on this.thanks.


Then you would have to pay for custom valve train development to spin high rpm. VE at that sort of RPM would be a problem because the head was not designed to flow that much. It might be interesting but expensive, no reason to do this unless you have lots of money.

The cam profile on the KA is limited by the lifter bucket diameter as well.

Mike


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## SVP5TEN (Apr 27, 2004)

morepower2 said:


> Then you would have to pay for custom valve train development to spin high rpm. VE at that sort of RPM would be a problem because the head was not designed to flow that much. It might be interesting but expensive, no reason to do this unless you have lots of money.
> 
> The cam profile on the KA is limited by the lifter bucket diameter as well.
> 
> Mike


now are you talking with a stock or prepared head?. or does it even matter because the head wont flow as much?. also since we are using a long rod. it would provide long piston dwell at near top dead center. creating more VE from mid to higher rpms. but since we are more concerned about the low flow design of the ka head, valve diameter, cam size , intake runner length/diameter, exhaust length/diameter, carb size or injectors etc.. would help increase VE. as well as port and polishing. now would this help the ka head come from low / mid range to mid / high range rpms?. 
Patrick


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## morepower2 (Apr 19, 2002)

SVP5TEN said:


> now are you talking with a stock or prepared head?. or does it even matter because the head wont flow as much?. also since we are using a long rod. it would provide long piston dwell at near top dead center. creating more VE from mid to higher rpms. but since we are more concerned about the low flow design of the ka head, valve diameter, cam size , intake runner length/diameter, exhaust length/diameter, carb size or injectors etc.. would help increase VE. as well as port and polishing. now would this help the ka head come from low / mid range to mid / high range rpms?.
> Patrick


THe issue is the KA is undeveloped so you would have to buy a custom billet crank, custom rods, have your head flowed sacrificing several in the R&D process, develop a valvetrain which would include somehow instilling bigger buckets. I mean it would literaly cost thousands and thousands of dollars. Its doesnt make sence to do so unless you are racing in a class where you gotta run the KA.

Mike


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## SVP5TEN (Apr 27, 2004)

morepower2 said:


> THe issue is the KA is undeveloped so you would have to buy a custom billet crank, custom rods, have your head flowed sacrificing several in the R&D process, develop a valvetrain which would include somehow instilling bigger buckets. I mean it would literaly cost thousands and thousands of dollars. Its doesnt make sence to do so unless you are racing in a class where you gotta run the KA.
> 
> Mike


ahh....so it probably wont be worth it, but then again it would be interesting to do. you just helped me find some weaker points to work upon.helps me with my hybrid.


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## morepower2 (Apr 19, 2002)

SVP5TEN said:


> ahh....so it probably wont be worth it, but then again it would be interesting to do. you just helped me find some weaker points to work upon.helps me with my hybrid.


Interesting yes but unless you ahve a reason to do this, it will cost more that its worth and insane for a street car.

Mike


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## SVP5TEN (Apr 27, 2004)

morepower2 said:


> THe issue is the KA is undeveloped so you would have to buy a custom billet crank, custom rods, have your head flowed sacrificing several in the R&D process, develop a valvetrain which would include somehow instilling bigger buckets.


ok, now im a little confused. while i do agree with you on developing a valvetrain and some how getting bigger buckets installed. ive just recieved an email back from Mack @ www.mckinneymotorsports.com. ive asked the same question. and mack writes,''The ka is a cam on bucket desogn so the cam
and bucket are not the problem..". so im a little confused. any one care to toss in .02 more cents?.
patrick


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## morepower2 (Apr 19, 2002)

SVP5TEN said:


> ok, now im a little confused. while i do agree with you on developing a valvetrain and some how getting bigger buckets installed. ive just recieved an email back from Mack @ www.mckinneymotorsports.com. ive asked the same question. and mack writes,''The ka is a cam on bucket desogn so the cam
> and bucket are not the problem..". so im a little confused. any one care to toss in .02 more cents?.
> patrick


basicaly he wants your business and I am telling you what its going to take. To consider destroking and reving the motor really high like 9000 rpm, you are going to need a big enough cam to do so. The ramp profile is limted to in part by how much rubbing area you have on the bucket. Too radical a profile and you run off the end.

If you run VQ or QR lifters (which will work) and notch the cam bucket boss in the head a little you gain another 1.5mm of space or so and can run a more radical cam than any on the market, in fact JWT has experimental grinds that are not tested or sold yet that use this.

However to make power out to 9k you need something much more radical than this, so you probably have to machine the head to take northstar or some other buckets and hire a real cam design consultant of which their are probably 3 in north america who are afforable and any good.

Now if you wanted to try something more mild, then look at some of the NAPSZ cranks and choose a shorter stroke and makes some rods and pistons to stuff something longer in there and then go to QR, VQ or newer Altima KA Alloy one piece buckets. This is proably not as radical as you want but it would be more afforafable.

So to build a motor thats capable of exploting a short stroke and long rod, its going to take a lot of money and you will be treading on new ground for the KA. The motor would not be too streetable either. It would have a 1500 rpm idle and very little bottom end power. For a street motor, I would probably suggest just running forged pistons and rods and running a good turbo and limiting your self to 7500 rpm.

Mike


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## SVP5TEN (Apr 27, 2004)

morepower2 said:


> basicaly he wants your business and I am telling you what its going to take. To consider destroking and reving the motor really high like 9000 rpm, you are going to need a big enough cam to do so. The ramp profile is limted to in part by how much rubbing area you have on the bucket. Too radical a profile and you run off the end.
> 
> If you run VQ or QR lifters (which will work) and notch the cam bucket boss in the head a little you gain another 1.5mm of space or so and can run a more radical cam than any on the market, in fact JWT has experimental grinds that are not tested or sold yet that use this.
> 
> ...


thanks for the great info mike. ill keep studying about it in the mean time keeping my decisions open. but i am determined to get this destroked ka idea going. you gotta pay to play, and i wanna play.:thumbup:. now how much of an over bore can i run on the ka block?. idealisticly a 91 bore would be playing it safe. but for the loss of displacement due to the crank i can lose a hefty amount. now for my stroker lz2.3 ive ran the over bore 3.5mm. for the ka id like to try and get 4-5mm overbore. getting a little thin. possible you think?. any way to get stronger sleeves, then over bore?.


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## Asleep (Jan 19, 2003)

on a sidenote, modified mag did an article sometime back on the flowing of the ka head. i cant remember the results off the top of my head, but the newly ported head flowed something like 85% over stock... on the bench at least, it looked like it was going to be sweet in the real world.


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## morepower2 (Apr 19, 2002)

SVP5TEN said:


> thanks for the great info mike. ill keep studying about it in the mean time keeping my decisions open. but i am determined to get this destroked ka idea going. you gotta pay to play, and i wanna play.:thumbup:. now how much of an over bore can i run on the ka block?. idealisticly a 91 bore would be playing it safe. but for the loss of displacement due to the crank i can lose a hefty amount. now for my stroker lz2.3 ive ran the over bore 3.5mm. for the ka id like to try and get 4-5mm overbore. getting a little thin. possible you think?. any way to get stronger sleeves, then over bore?.


It would have to be sleeved for sure but due to the tight bore spacing, I don't think you can do tighter than 91mm.

I have an idea, the SR20 and KA cranks are close. You have to remachine the thrust area skinnyer and do some stuff to the pump drive on the snout but there is a low buck posiblitly there. Plus the SR crank is fully counterweighted. I would start measuring.

Mike

Mike


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## morepower2 (Apr 19, 2002)

Asleep_94_Altima said:


> on a sidenote, modified mag did an article sometime back on the flowing of the ka head. i cant remember the results off the top of my head, but the newly ported head flowed something like 85% over stock... on the bench at least, it looked like it was going to be sweet in the real world.


That is not posible, more like 25% more than the stock head or the stock head flows 85% of the modified head..

Mike


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## Asleep (Jan 19, 2003)

i wont try and sound like i know for sure. it was a while back. i tried to find the article on the net and couldnt do it. maybe 85 was an exaggeration  but i know the dude expressed surprise and enthusiasm for the amount of flow he was able to get out of it.


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## SVP5TEN (Apr 27, 2004)

morepower2 said:


> If you run VQ or QR lifters (which will work) and notch the cam bucket boss in the head a little you gain another 1.5mm of space or so and can run a more radical cam than any on the market, in fact JWT has experimental grinds that are not tested or sold yet that use this.
> 
> Mike


just crossed my mind. when using vq or qr lifters, i would gain another 1.5 mm of space. now to run a more radical cam, would it have to be rewelded and grinded down to a certain lift and duration to adjust to the gain of the extra 1.5 space.


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## morepower2 (Apr 19, 2002)

Asleep_94_Altima said:


> i wont try and sound like i know for sure. it was a while back. i tried to find the article on the net and couldnt do it. maybe 85 was an exaggeration  but i know the dude expressed surprise and enthusiasm for the amount of flow he was able to get out of it.


25% is considered to be excellent results.

Mike


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## morepower2 (Apr 19, 2002)

SVP5TEN said:


> just crossed my mind. when using vq or qr lifters, i would gain another 1.5 mm of space. now to run a more radical cam, would it have to be rewelded and grinded down to a certain lift and duration to adjust to the gain of the extra 1.5 space.


To just use the VQ lifter, I suggest just sticking to the JWT stage 2 cam. This is the most radical profile that will fit on this size bucket. To go more radical then you gotta find a even bigger bucket and machine the head to take it.

Mike


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## Asleep (Jan 19, 2003)

i found the article i was looking for on flowing an s13 head.
Modified Mag issue 6/03 pg. 118. 

before/after
90.45cfm/106.65cfm intake
87.75cfm/121.5cfm exhaust
these measurements were taken at .100" lift. 
not bad, the numbers get even better obviously, as lift increases.


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