question about grinding the crank..

[motoman399]

so i was talking with the auto shop teacher at our local high school. he races nissans in some certain class (not sure what one) but he runs a ka24de that is all motor and i think it puts out around 230hp or so. he was telling me if i were to run honda rod bearings and grind the crank i could turn 8000rpm all day long. im assuming that the honda bearings are thicker than ones you can buy for a stock ka. has anyone heard of doing this? if so what series honda bearings would i buy. i think i have heard of this for sb chevy's too.

[Razi]

I think it's the partially balanced crankshaft that's stopping the KA from revving so much.And the long stroke.

[480sx]

Your autoshop teacher doesnt sound like he knows what the hell hes talking about, or is just messing with you.

First, why would you want to grind the crank to use honda bearings? Or is he talking about knife edging the crack and balancing it or something..

Second, honda bearings are probably not going to work on a Ka24de. That idea is just redic. The Ka has a weird thrust bearing/main center bearing. All the hondas have separate thrust bearing.

Third.. WHY would you want Honda bearings? Rotf, honda bearings arnt going to make your car magically handle revs better.

Crank harmonics are what kill a Ka's rev potential. An aftermarket dampener, a balanced, knife edged crank, and a built head and you can rev it out better. It will never be a honda simply by design, the motor was never intended for high rpm operation.
Modified by 480sx at 12:45 PM 12/3/2008

[WDRacing]

Why crank up the rpms when you can add boost!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[motoman399]

Your autoshop teacher doesnt sound like he knows what the hell hes talking about, or is just messing with you.

First, why would you want to grind the crank to use honda bearings? Or is he talking about knife edging the crack and balancing it or something..

Second, honda bearings are probably not going to work on a Ka24de. That idea is just redic. The Ka has a weird thrust bearing/main center bearing. All the hondas have separate thrust bearing.

Third.. WHY would you want Honda bearings? Rotf, honda bearings arnt going to make your car magically handle revs better.

Crank harmonics are what kill a Ka's rev potential. An aftermarket dampener, a balanced, knife edged crank, and a built head and you can rev it out better. It will never be a honda simply by design, the motor was never intended for high rpm operation.

Modified by 480sx at 12:45 PM 12/3/2008

actually he had one of the fastest cars out there it was some circle track. when your crank gets grooves in it from a spun bearing or from oil you have it ground (resurfaced) and you can get that in so many thousands. the way i see it is when you grind the crank and add thicker bearings you would have less surface area and that would be less friction??? and you wouldnt add honda main bearings or thrust bearings. lol just rods

Why crank up the rpms when you can add boost!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

well of course you would add boost.. i wouldnt be posting this in the ka-t section if i wanted to stay N/A haha. the teacher had to stay N/A to be in the class.

[480sx]

Yea i mean i know why you grind cranks and use oversized bearings..

For a performance high HP motor you dont want oversized bearings at all. The bigger the bearing, the smaller the journal on the crank. That puts more pounds per square inch of force on the crank itself and that leads to a weaker crank.

The idea about having less friction is kinda absurd.. Your not taking that much off to begin with to make a damn bit of difference as far as a power adder or whatever. Your still moving the same weight pistons, rods, crank and drivetrain.

In addition, a thicker bearing holds heat a lot more than a thinner bearing. You want a thin bearing so it will transfer heat better. If your going super oversized honda bearings or w/e your going to end up with a thick bearing. Also, your crank can only be ground down so much before it becomes out of factory spec, and should be trashed.

[WDRacing]

The KA24DE has already been proven to reach 8000 rpm with a professional balance job done on the rotating assembly. But I mean the entire rotating assembly, from crank pulley to flywheel. Then of course you'd need valve springs and cams that will breath that high up. But overall it's NOT as hard as people think to increase the rpm range by a mere 800-900 rpm. If you've got a good cam/turbo combination you're really only limited to octane. With an alcohol fuel you're limited to keeping the head from lifting and or cracking the block itself.

The intake is a restriction past 500whp, but not so much that it requires a new one. Would it free up top end power, yes, but the short runner big plenum version kill your low/mid power curve.

WD

[motoman399]

ok well i see both your points. i think im going to research it more before i completely throw out the idea. thanks

[Crazyirish]

ok well i see both your points. i think im going to research it more before i completely throw out the idea. thanks

I attended the race car program at my local community college and one of my teachers told us that it was impossible for an engine to have 100% or higher volumetric efficiency.

Just because someone is a teacher, it doesn't mean they know what they are talking about.

[motoman399]

impossible for an engine to have 100% or higher volumetric efficiency.

what is this?? explain please

and

Just because someone is a teacher, it doesn't mean they know what they are talking about.

lol

[Crazyirish]

http://en.wikipedia.org/wiki/Volumetric_efficiency

I didn't bring that up because it was related to the situation at hand, I was just pointing out that in this field (all fields really) you will meet a large number of people who don't know wtf they are talking about. One of the reasons I love nico and the ka24et/ka24det subforum in particular is that anyone who spreads misinformation generally gets shot down pretty quick.