SR20DET Top end with a KA24E bottom end

[Silvia54]

I have noticed as of late that there have been a lot of articles in the tuner mags about honda engines where they take the bottom end of the K24 and put the top end of the K20 on it. I know these engines are related but chould the same be done with the KA and the SR. The KA has a stout bottom end, more displacement and the old ones have low compression. The top end of the SR is made for more sporty applications and revs better in stock form. This may be totally crazy and might not work at all but I was just thinking about it and wanted to put it out there. Could it work? If so wouldn't you be getting the best of both engines? You would basically have an SR20 with 2.4 Liters of displacement. I guess an SR24? Just a thought.

[Emagdnim]

I would think just because they have 2 different displacements that the head would need to be modified. There may be emisson problems too but I don't think it would be impossible. I do think it would proably be impractical.

[nissanguy_24]

Literally stuff on the KA and SR dont line up. But the real issue is theres no point to it. There isnt a huge difference between the two heads. Its not like swapping on a Vtec head and gaining 40 horse power. The closest thing the S chassis cars has is the KA24E + DE head to make a 11.7:1 compression ratio KA24.. no ones really dynoed one of these yet, but it wouldnt surprised me if you could net 20-30 horse power from this swap starting with a KA24E... if you can make it run and everything.

[raging panda]

someone said they flow tested the KA head and it is actually better than the SR head. I dont know why you think the SR head flows better or revs better, but I dont think its true

otherwise, the nissanguy said was all right. If you want a high displacements SR, get a stroker kit. Nissan didnt make any of their blocks mate up with any other series heads.

[nissanguy_24]

one thing to add, the SR's revs dont came from its valve train.. Thats not the KA's limitation. Hell the KA and Sr's valve train are very very similar the problem with the KA revving is the long stroke.

['97 S14 SE Turb]

KA's heads does flow more than the SR's head. It has to feed 2.4L vs 2.0L.

Also, a quick look at the valve size says a lot more too. Bigger valves on the KA.

Limitation of the KA for high rpm work is it's long intake manifold design. That manifold is designed to give midrange power.

It's valvetrain is infact better than the SR's design. It's the traditional cam on bucket design, unlike the SR's Y-shaped rocker arm design where overeving the motor would chuck a rocker, trashing the valves, and cams. The fix is a $80 rocker arm stopper plate.

KA, with a different intake manifold, something designed for high rpm, acts very differently. Heck, with the JWT Stage 1 Street Cam, it pulls hard all the way to redline. Even with a JWT revised redline of 7,200 rpm, it gets there fairly quick.

When it gets turboed, reving the motor to redline is not an issue. Get there even faster.

And then when you go to a lightweight flywheel, even better...

Remeber, a lot of what people say about the KA being unrev happy is what it is stock. It's what the manufacturer designed it for. Mid to upper range power...

Once you start to modify the engine, it behaves quite differently...

['97 S14 SE Turb]

Originally posted by nissanguy_24
Literally stuff on the KA and SR dont line up. But the real issue is theres no point to it. There isnt a huge difference between the two heads. Its not like swapping on a Vtec head and gaining 40 horse power. The closest thing the S chassis cars has is the KA24E + DE head to make a 11.7:1 compression ratio KA24.. no ones really dynoed one of these yet, but it wouldnt surprised me if you could net 20-30 horse power from this swap starting with a KA24E... if you can make it run and everything.

It's actually more like using the KA24E piston in a KA24DE that gets you that compression ratio...

And for the record, NASPORT (a racing series in the west coast) have 240SX tube frame race cars. These run carbed KA24E. Over 300 hp. Redline of 8k rpm (stock crank)

A streetable version is rated at 244 crank hp. One Norcal owner has one in his car. Very nice setup.

[ToplessFC3Sman]

Also, with the honda engines, correct me if Im wrong, the K24 is just a bored out version of the K20. So the heads would naturally fit and have everything lined up, they may just need to be machined a little bit to get the smaller-diameter head to match up with the bigger diameter block. With the KA24 and SR20, they are completely different engines, so bolt patterns, seals, and even where the cylinders are in respect to the heads (spacing between them, etc) would be different, making it physically impossible without a hell of a lot of work. Plus everything everyone else has said lol

[nissanguy_24]

Originally posted by '97 S14 SE Turb
It's actually more like using the KA24E piston in a KA24DE that gets you that compression ratio...

And for the record, NASPORT (a racing series in the west coast) have 240SX tube frame race cars. These run carbed KA24E. Over 300 hp. Redline of 8k rpm (stock crank)

A streetable version is rated at 244 crank hp. One Norcal owner has one in his car. Very nice setup.

Any combination of those pistons and that head will produce those kind of compression ratios.. Considering that those are the two things determining it.. but i shouldnt have to tell you that.

As for the nasport cars' ive heard of the race version but never the street versions, do you have any more information on these cars?

And when i said the limitation of the KA's revs wasnt its head.. what i ment was the limitation of being able to rev way past the redline. Its much more difficult to make a 8k rpm KA then a SR.. I didnt mean to imply it cant make power uphigh.. everything on that car is set up for midrange, like the intake manifold and camshafts, but those can be overcame easily.. Well i dont know about the intake manifold. Is there any aftermarket ones out there yet? deffenately a lack in the industry..

[hachiroku-fc3s]

Originally posted by nissanguy_24
There isnt a huge difference between the two heads.

Yeah, no. I guess they both............are cylinder heads, but '97 has already outlined that the heads of these two engines are quite different. As for the initial question, it too has been answered. It is quite impossible. I mean, sure, you could somehow strap in on there, but it would never work right. The bore centers are off. I don't know the numbers off the top of my head (could look em up quickly) but I believe that the KA cylinders are spread out further, especially the center two more than on the SR, nothing would line up. Now, if toda wants to get into making aftermarket KA heads, that would be an option, but no Frankensteins.

[nissanguy_24]

The difference he stated were, for the most part, related to the displacement. Nothing a valve and port job on a sr can't fix.. My point is it is not like a honda setup where one head is equiped with vtec and has a huge advantage over the other.

[hachiroku-fc3s]

Originally posted by '97 S14 SE Turb
It's valvetrain is infact better than the SR's design. It's the traditional cam on bucket design, unlike the SR's Y-shaped rocker arm design where overeving the motor would chuck a rocker, trashing the valves, and cams. The fix is a $80 rocker arm stopper plate.

This is what I was talking about. Oh and the rocker arm stopper doesnt work. I had a second SR-ed friend kill his engine Wednesday. Well not kill it, but how many weeks is he gunna have to wait to get parts because he lost a valve somewhere in his head?

['97 S14 SE Turb]

Originally posted by nissanguy_24
The difference he stated were, for the most part, related to the displacement. Nothing a valve and port job on a sr can't fix.. My point is it is not like a honda setup where one head is equiped with vtec and has a huge advantage over the other.

Well, can't exactly physically fit the same size KA valves into the SR head without some major, major work.

Going back to the topic, the real limitation is this.

KA24DE runs a dual stage timing chain, where as the SR runs a single stage chain. Because of that KA's timing gears can be smaller, and the cams placed closer together.

SR's single stage chain, well, larger cam gears.

One thing that I see some folks like to talk about is the valve angle. They always claim the SR's valve angle is much greater than the KA. They base that on the physical width of the valve cover. That doesn't tell the whole story. For those who are familiar with the SR, you know how the cams sit outboard of the valve location, using the Y-shaped rockerarm/follower to open the valves. And having the hydraulic lash adjuster sit outside of that. A setup like that takes up much more physical space.

['97 S14 SE Turb]

Originally posted by hachiroku-fc3s
Yeah, no. I guess they both............are cylinder heads, but '97 has already outlined that the heads of these two engines are quite different. As for the initial question, it too has been answered. It is quite impossible. I mean, sure, you could somehow strap in on there, but it would never work right. The bore centers are off. I don't know the numbers off the top of my head (could look em up quickly) but I believe that the KA cylinders are spread out further, especially the center two more than on the SR, nothing would line up. Now, if toda wants to get into making aftermarket KA heads, that would be an option, but no Frankensteins.

Actually, the bore center is the same... There have been talks of using the KA crank in the SR...

Realistically, doing that, it would be easier to stick to the KA in the first place. Having a head that can actually flow enough air for the displacement without some major major head work.

['97 S14 SE Turb]

Originally posted by nissanguy_24
Any combination of those pistons and that head will produce those kind of compression ratios.. Considering that those are the two things determining it.. but i shouldnt have to tell you that.

As for the nasport cars' ive heard of the race version but never the street versions, do you have any more information on these cars?

And when i said the limitation of the KA's revs wasnt its head.. what i ment was the limitation of being able to rev way past the redline. Its much more difficult to make a 8k rpm KA then a SR.. I didnt mean to imply it cant make power uphigh.. everything on that car is set up for midrange, like the intake manifold and camshafts, but those can be overcame easily.. Well i dont know about the intake manifold. Is there any aftermarket ones out there yet? deffenately a lack in the industry..

A NA tuned KA, with the following:

JWT ecu
intake
header
testpipe
JWT S1 cams
75mm exhaust (60mm N/A, for SR, is too small for NA KA)
lightweight flywheel.

can run to redline fairly quickly... Will pull like a H22... (only to 7200rpm)

There's not enough R&D to figure out the proper intake manifold for KA. I personally gave up on NA tune, because it takes plenty of money to get the power a turbo can easily get.