KA Stroker

[Tatanko]

Ok...then it appears the only kind of increase in displacement even possible for the KA is boring it out to 2.5L like KAJosh did? I would ask, "what will I need to replace to rev higher with the KA?" but it's painfully obvious the KA sucks at high RPM's anyways, so it's pointless.

EDIT: This is becoming pointless...this makes me wanna say "f*** it" and get an RB20...anyone agree with me on that idea? RB20's aren't that expensive are they? Where would I get it from?
Modified by Tatanko at 4:16 PM 9/9/2004

[Red-KAT]

If I had all my cash back from the turbo...

I would go RB20 or 25

[Tatanko]

RB20 it is then...

[GlacierFreeze]

Tat, if you destroke the KA to rev higher and do nothing else, yes it will suck at high rpms as it does now. You have to take advantage of being able to rev higher by getting bigger cams and a custom short runner intake manifold, both of which shift the power band into the upper rpms. Soooo destroking + bigger cams + short runner intake manifold = top end monster and loss of tq down low.

[Tatanko]

Wouldn't that be the same as an....SR?! This is a KA, it's torquey, please let it keep it's torque. There's more to performance than top-end HP. But I do see what you mean.

[GlacierFreeze]

Have to sacrifice low end tq for hp and vice versa. No way around it. The stock KA is good for atleast 7200 rpms. Just get some bigger cams. No need in destroking to 2.2 or lower to rev over 8000 rpms and losing a lot of low end power.

[Red-KAT]

You may loose TQ but I think its a good trade-off...

If you can hold youre car in gear longer... You will be faster.

Shifting takes a long time. And if you could manage all youre power between 4000 and say 8000... Thats allot to work with.

It would be allot like a stroked SR20...

[SeVa-S13]

Thanks for the vote of confidence but alot of the time I'm just arguing for the sake of debate/conversation--I find it's the best way to learn, especially when I'm wrong.

And no, I don't consider a stock 240 a true sports car.

I understand your wanting more all around power but unfortunately stroking (heheh) alone isn't the best idea, and the KA block doesn't have too much room left to bore it out. Cams and headwork will do wonders for your powerband and overall power but the KA is still limited as far as its displacement goes. =\

As for the destroking thing, I was not saying that's the best way to make power, I was just noting that some (pretty hardcore guys mind you) people have made hybrid engines such as the Z/KA22 for the purpose of NA racing. Of course to compliment this higher revving ability you'd want some valve train upgrades and a better set of cams to suit the higher air flow.

Ok, on to my favorite subject, RB's. My RB20 is exactly how I think a racing engine should be set up--the higher it revs, the more power I get. Its stock redline of ~7600 is a bit conservative and you can hit almost 8500 with the stock valvetrain but it's not advised to do so often. But with simple upgrades and a set of RB25 cams (a great upgrade and bolts right in with no modification), the little motor screams and can make power to and past 9k. (Blueprinting and balancing is your friend at that point.)Now, being undersquare it doesn't have the great low end like a V8 or a nicely tuned KA, but anything above 4k is bliss. And it only gets better as the tach climes. Not to mention the V8 sound, but that's just a little quirk of mine.

[GlacierFreeze]

If I were gonna get an RB, I'd go 26 heh. Redlines at ~8.9k and BPU can get you near 400hp. Yikes.

edit... Enough of this RB jibberish, this is KAT forum hahaha.

[Tatanko]

So what if it's a KA forum? This thread is done for anyways Heh, I never knew the RB20 was capable of revving that high. Anything above 4000...hmmm....I'm sure there must be ways of increasing the torque to good daily driving levels, right? (Or is it up there already?) At this point I'm seriously considering the swap...since it's just as cheap as a KA-T setup and I'll end up with a lot more from it.

KEEPING ON THE SUBJECT OF STROKING AN ENGINE (lol), I've noticed the RB25 and RB26 both have a longer stroke than the RB20 (each one using another 0.5mm to gain part of it's increased displacement). Would it be possible to use the crank/rods out of the RB26 to make a 2.1L out of RB20? I know, you're probably thinking to yourself, "Oh god, here we go again, he wants to stroke an engine instead of revving it high," but would a measly 4mm increase in the stroke honestly hurt it's revving capabilities that much? With an upgraded valvetrain, could I still rev to points like 8500 RPM like you mentioned? I can't see why I wouldn't since the RB26 does...and that extra 0.1L might be good for some more torque to balance out with the HP. Not to mention more power from the same amount of boost fed into the engine. Any thoughts?

[SeVa-S13]

Actually your question is a very interesting one because plenty have people have done it. With the popularity and success of the GT-R and its famed RB26DETT, alot of the RB20 guys felt a bit, well lacking. Plus, GT-R's are expensive to buy and the insurance is much like owning a Corvette at 21. So what they did is figured out that they can use stock RB26 pistons and cranks in their 20's. Pistons or crank alone yield around a .2 liter displacement increase, and combine for what's known as an RB24. Tomei actually sells crate engines like the RB22 and 24, but no one should have that much cash laying around. Now of course the pistons or crank alone would dramatically change the bore vs stroke ratio of the engine, changing alot of the characteristics of the engine. Of course just pistons will give you a motorcycle engine and crank will give you a cross between a KA24 and RB25 style engine, which seems to be your aim. Now of course swapping cranks will be a rather in-depth procedure and will probabaly require minor modifications but never having done it, I can't say.

Oh, andthe RB26 does not redline at 8900 stock. The 20 and 26 are very capable of high rev's but it takes work and proper mods. (BTW it's 8200 for the R32 and they actually lowered is to 8000 for the R33 and 34.)

[Redline240]

I think your questions would be better suited in the RB fourm...especially since there's only a few RB guys that view the KA fourms...

So back to the KA...i think the biggest complaint with the KA is its 6500rpm limiter and everyone saying it not gonna go much higher...well frankly thats not true, it just isn't being done...if you can get a 350ci to run over 10k rpm then why can't the KA...

I'm not looking for 10k, but what would it take to get 7500-8000k out of a KA? Any why is it that the stock forged rods are ok for 400hp but everyone says not to use them to rev over 7k?

Obviously a intake manifold with larger plenuem, shorter runners...pnp...cams with higher duration...what about more lift? Would new springs, valves, head gasket be needed?

Redline

[SeVa-S13]

Titanium springs and retainers would be need for very high revs. Oh, and the reason for not revving too high deals with physics, tensile loads and all that jazz.

[GlacierFreeze]

Oh, andthe RB26 does not redline at 8900 stock. The 20 and 26 are very capable of high rev's but it takes work and proper mods. (BTW it's 8200 for the R32 and they actually lowered is to 8000 for the R33 and 34.)

Whoops, thanks for the correction. I must have seen specs or something from a modded skyline.