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Z24i INFO/Performance?


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#1 Labanon

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Posted 12 June 2009 - 07:16 PM

Anyone know of some good reading sites for the NAPS Z24i :blink:. And a good cheap site where I can buy a dual side draft manifold, cam, header, ignition upgrades, anything performance wise for my new engine. Even a busy Hardbody site where I can snag up some used parts for it would be great. Just looking for bolt-ons mostly. I'm not trying to build a beast of an engine, just gonna try to make it quick LOL :rolleyes:. Thanks in advance fellow ratsuners.

#2 datsunfish

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Posted 13 June 2009 - 10:30 AM

I would suggest finding carbs and manifold on ebay. You wont find a cam upgrade for a naps z engine since the valves will interfere with eachother with too much cam lift. Headers can be found on ebay as well. A naps already has electronic ignition but you can upgrade compression side with msd coil. Not sure that will do much. A nap z head will do well with some intake porting I have heard. We commonly refer to the naps as the "nissan anti performance system". You could also shave the head a bit or maybe even put in some KA pistons for higher compression. They sould be the same size with smaller dish on top.
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#3 steve g

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Posted 13 June 2009 - 02:50 PM

there are so many sides to a topic like this....... if i were you i would stick with the stock fuel injection..... there are a few computer mod companies that can rework the brain to suit your needs. Cams are very limited.. i dont suggest the mikuni cam because its a tad too radical in my opinion, crane cams makes one also but from what i heard there is not much gain. playing with the stock cam and re degree it with an adjustable cam gear has always had me wondering if there is some power hidden in the stock parts.... I have experienced pacesetter headers even on a dyno and there is no gain with thier cheap products..... they look cool, sound cool, leak great, and sound fast.... thats all they have to offer.
If you lean twards a KA head you basically have a KA motor.... so thats another post i guess.
The stock naps z24 head actually has a better torque potential than the KA head.... Sidedraft carbs rob torque.... so can headers and cams..... if you have a 4x4 720 dont bother..... keep it stock..... if its a 2wd than skys the limit ( hopefully your credit card has the same)

#4 datzenmike

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Posted 13 June 2009 - 04:28 PM

Stock Z24i compression works out to only 8.25. Adding KA24E pistons will bring it up to 9.51

The Z24/Z24i was designed for low emissions. Emissions can be controlled more easily if the motor is designed to run in a narrow power band usually no higher than freeway speeds. Say under 4,000 RPMs. The head does not have to breath well because it isn't needed above 4K. Valve springs won't support high revving because they never go there. Compression can be low 8.3.

Advantages:

The NAPS head is very close to the ideal detonation resistant HEMI shape. The head is a flow through design.... ideal for turbo applications with lots of room on the exhaust side of the motor. Each cylinder has dual plugs to allow high levels of EGR, BUT it also shortens the burn time and allows less timing advance. The Z24i comes with a hi-volume oil pump. Always a good idea.



The block and internals are what keep a motor alive, but power, is made in the head and at higher RPMs. It contains the cam and valve train as well as the intake and exhaust ports.

The Z24 valves are slightly longer but the same size as the L20B motor... so they would be slightly heavier. Heavier is not good as the valve springs are unable to keep the valves closed at higher revs. The Z24 'runs out of steam' above 5,000 RPMs. (often much lower) Partly due to poor breathing (more on this) but often weak, tired valve springs. A stiffer valve spring would be an excellent idea to allow your other improvements to work at 5K and above. The valves are quite close together and opposite each other arranged in a VEE . Larger valves and higher lift cams run the risk of the valves touching each other.

Both intake and exhaust ports are horizontal with a sharp bend just before the valve pocket. Look at any L or KA head and see how high up the ports are from the head surface. The Z ports is very close to the head gasket which forces a tighter bend in the short turn radius. This bend acts as a restriction to flow like a kink or tight bend in an exhaust pipe. Additionally, machining for the valve seat always leaves burrs and a poor transition to the port walls. The short turn radius is acute! There is lots of room for improvement here. Gasket matching is imperative. With the disadvantage of these ports, EVERY advantage no mater how small is needed.

The Nissan ignition system is good enough. After-market units are hard on the wallet and the gains are psychological... if I spend $300 it's just got to run better... right? Someone show me a dyno sheet with definitive proof of a substantial gain that is worth the money spent. Same with a header. May even loose some bottom end torque with one for a few hp at 6K? Poor return on the investment unless on a heavily modified engine. Again, it's got to run better, for the $200 spent, right?

Edited by datzenmike, 13 June 2009 - 04:31 PM.


#5 steve g

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Posted 14 June 2009 - 07:47 AM

stroke it! thats my plan

#6 datzenmike

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Posted 14 June 2009 - 08:03 AM

Stroke it? The Z24 is as far as you can go short of a custom crank. Then you would need custom rods..... I would turbo it. The cross flow design is well suited for this and a turbo doesn't care as much about port flow as a NA carb motor.

Yes, grafting a KA head on to a Z24i would basically make a KA motor... but, it would be about 100 lbs lighter. You would have to use KA pistons, and use the Z24 rods, they are much more beefier. The KA head would more easily allow multi-port EFI and turbo.

#7 steve g

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Posted 14 June 2009 - 08:19 AM

for a long time i was trying to figure out how to get alot more torque out of my z24i. eve.n considered a ka head and so on..... but after annoying a good customer of mine who owns an engine shop that specializes in pro-stock builds he finally told me im wasting my time..... the bottom line like we have heard many times before,,, no replacement for displacement.... of course a turbo can simulate larger displacement.
My stock z24 crank can be offset ground for about $400. he didnt look at the rods but he said generally you can run the stock rods as long as the wrist pin is still low enough in the bore after the offset.. custom pistons are almost always a must..... This is my plan for some extra power
Steve

#8 datzenmike

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Posted 14 June 2009 - 09:05 AM

Agree with the displacement comment by Shelby. Can you explain how the stroke is increased on the crank?... sounds interesting. Stock Z24i and KA piston pin height is 34mm from center line pin to piston top. Rod lengths are 165mm. The closest rod length under this is the Z20E at 152.5mm. That's a bit too much.

Edited by datzenmike, 14 June 2009 - 09:10 AM.


#9 steve g

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Posted 14 June 2009 - 09:19 AM

hey mike,
one of my former customers (now a good friend) bases his entire life and income on building racing engines. One thing he is well known for is offset grinding cranks to gain stroke. What he does is takes the rod journal on the crank and bacically adds a crapload of weld on the outer part of the journal, then he marks a new journal centerline out further than its origional location. at that point he turns the journal surface till smooth back down to factory journal size but the journal is out further than stock. This can also be dont the opposite way to destroke. There is alot more to it but thats the simple version.
4 bangers are fairly cheap to do because its only 4 journals and balancing is not as complex as a v8 crank.... V8 cranks are astronomically expensive.

#10 datzenmike

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Posted 14 June 2009 - 01:25 PM

OK. I see now, you have to add metal.

Hmmm, If the crank throw were welded up and made about 13mm longer the 152.5 Z20E rods would work with the stock pistons. Wow, the motor would be just over 3 liters and have a 10.21 compression.

Seriously, I doubt the piston skirts would clear the crank throws at BDC. But fun to think about.

#11 steve g

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Posted 14 June 2009 - 04:49 PM

13mm!!!!!!????????? wow you think big! generally no more than 15% is offset and thats under perfect conditions... so like 2 or 3mm's ans that would provide like what?.....2.6 litre? The big gains is when its done on v8 motors because the displacement adds up fast... but every bit helps even on a tiny motor. Yes if you somehow offset it 13mm you would probably have pistons and rods sitting in oil at bdc..... so i wonder about cylinder extensions....yeah, it could be done:blink:

#12 datzenmike

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Posted 14 June 2009 - 05:21 PM

:D Oh, well. 13mm was so you could use readily available Z20E rods... but I guess not. I worked out a stock Z24i with a 3mm or 6mm stroke increase and it's a 2,536cc motor. Need 3mm shorter rods.

#13 Labanon

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Posted 15 June 2009 - 02:02 AM

So I should get some stiffer valve springs, Ka pistons, I'm not going turbo. The engine's going into a 320 pick up. Not trying to get into the 12's at the strip, just trying to build something thats really fun to drive. The KA head swap seems like a little too much, just to end up with a KA engine. Will the manifold for a dual side draft L engine work on my NAP Z? My freind has a toyota truck thats not running with a set of side drafts on it. Could prolly get a pretty good deal for it. Thanks guys some pretty good information so far.

#14 datzenmike

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Posted 15 June 2009 - 06:50 AM

Sorry, the L head side drafts wont bolt to the Z24 NAPS head. You could skip the KA pistons and put an L head on the Z24 to raise the compression and use those side drafts. The L head swap is well documented and has far superior breathing. Brian hang_510 has one I think.

#15 napz510

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Posted 15 June 2009 - 01:42 PM

Sorry, the L head side drafts wont bolt to the Z24 NAPS head. You could skip the KA pistons and put an L head on the Z24 to raise the compression and use those side drafts. The L head swap is well documented and has far superior breathing. Brian hang_510 has one I think.


By switching that, how much horse power will you get? I'm just asking because I used to have napz 24 with that KA pistons, crower cam, mikuni 44 side draft and made 149whp on mustang dyno. Using the L head will gonna make more?Thanks..

#16 steve g

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Posted 15 June 2009 - 02:22 PM

you are doing darn good if you got 149 to the rear wheels with a napsz24. An L series head will perform about the same but has alot more potential for modifications thus additional power is available with proper preparation.

#17 Labanon

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Posted 15 June 2009 - 04:31 PM

By switching that, how much horse power will you get? I'm just asking because I used to have napz 24 with that KA pistons, crower cam, mikuni 44 side draft and made 149whp on mustang dyno. Using the L head will gonna make more?Thanks..


where did you get your NAP Z24 dual side draft manifold from?

#18 datzenmike

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Posted 15 June 2009 - 04:52 PM

With just an L head on a Z24 you basically have an L24. This is a 20% larger L20B so if the L20B is around 100hp (on a good day) then the L24 should make about 120-125 hp. However the compression will go through the roof with this set up so to be optimistic say 135 hp. There are LOTS of cam choices for the L series from mild to wild. So you should be able to take it to 150 with cam 'n carbs.

Byron on here has an LZ22 with cam and carbs (recently to EFI) and makes an easy 138hp. 150 would not be impossible for an LZ24.

Again, to be fair we are comparing hp from two different dyno's. :D

#19 napz510

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Posted 15 June 2009 - 04:54 PM

where did you get your NAP Z24 dual side draft manifold from?


I had the hks brand and i think that's hard to find these days. But you can use the cannon manifold which is ok. Guys from Guam still use that motor to race until now.



The motor is with Ultramagnus.

#20 bigjoe619

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Posted 19 August 2009 - 09:27 PM

i have a set of headers, a dual side draft manifold and a head ported and polished with a schneider cam i have to find the specs i also have only 3 pistons with rods pressed on them with a set of rings to go with them for $500 hit me up 619 864-3754