Little Trucks, Big World

        OK so I have the old z24 motor outa my 85 nissan. I want to build something impressive with it! I dont want any power adders all motor with lots of torq being that its going in a 4x4. We all kinda started anther thread on head mods so I figured what the hell lets see what we all can come up with and Im gona try and build it.


        So this is my plan I wana bump the compression up. I hear that I can use ka24 pistons to do that I wana try and get 10.0-1 If possible. What I would like to try and do is stroke it. ButI cant but I cant find any stroker kits so Im curious if any1 has done it and know how its done. I dont like the idea of milling a aluminun head that is allready prone to blowing head gaskets.


        Next Im curious on what head I should use. I am planning on flow testing a z24 and a z22 head to see what I come up with. Dont worry ill take lots of pics and will post my findings! Im open to any other Ideas like putting a ka24 head on duno If you can do that or if it will do anything. Im gona hog the hell outa the exhaust side and port match the intake but I dont wana get to carried away cuz I want low and mid torq. Then im gona do some bowl work. Next is not sure how big of a cam Im gona go with Im running a 260 in my current motor it works good for a stock motor. But I think im gona go bigger


          There and some smart people on here with some really good Ideas! I myself this is the 1st 4 banger build Im gona try. Ive built a ton v8s mostly ford 302's. If this new motor im trying to build doesnt give me what I want im gona have to drop a ford 302 in it lol!

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The bigger the cam the more your likely to move power into higher rpms and lose low end torque.... You should look into putting an L series head on the top of your motor, I know it can be done on a z22 but idk about a z24. sealik in here did it to his z22 with pretty good success.

Sacrilege!!!!! L head on Z block!!!! :lol:  :lol:  lol yes that could be done for sure, the compression would jump to 9.45 and you would also need the manifolds.

Myself, if I had a good Z24 I'd like to modify a KA24E head for it. The E head is larger so it would need milling or welding to bring the compression up, but if rebuilding the motor just use KA pistons. This would make the same hp as a KA then... about 150. I would make my own intake and run R-1 carbs. Hmmmmmm....

z24+ka head+ka pistons= ka24 with shitty z24 block correct?

Essentially yes, however, I for one have never experienced the Z24 block failures that some here have.  Of course, I wasn't pushing a lot of power through the block (like with a turbo, or NOx)...  I have only experienced the head gasket problems, which I believe are just a symptom of an aluminum head on a cast block, which can be worked around.

I've only known one person who repeatedly cracked Z24 blocks, and he was using a 100hp shot of NOx on a regular basis.  And if I was going to do that, I think I'd at least try using a crank girdle to help support things, even though it wouldn't do much to support the top end of the block directly, it might help.

I think it would be a decent motor, and none of modifications needed to shoehorn a KA24 block into a 720, that's a big plus.

Mike, I'm with you on this, would like to do it myself but too many other projects in front of it! lol

the headgasket issue is from weak and fatigued deck surface and cracks in the head bolt holes.

 this is caused by bad castings..... i have had several z24 blocks maggged and sonic tested and proven to be junk even though they were good running engines before torn apart.

 Thats why so many have issues with unsuccessful head gasket replacements.... the deck wont stay flat.

if it was just because its an aluminum head on a cast block this would be a huge issue considering how many cars run this configuration

Well, perhaps, but you can have cracks at the head bolt holes and not have any issues sealing.  I've had sealing issues without cracked head bolt holes.  Aluminum expands at a much higher rate than steel.  These failures are due mostly to the deck surface having too much roughness, which acts like a micro file on the head gasket.  Head gasket failures with aluminum heads on steel are very common, just look into the Neon 2.0L motors.  It's solved by using an aftermarket MLS gasket.  We have MLS from Nissan, however, I'm not sure they had specified a smooth enough surface for both the head and deck.

If you think about where the most common head gasket failure is on these trucks, it's usually between 3 and 4.  A head expands from it's center out, so that would explain why even though there is a much smaller gap between 2 and 3 than 1 and 4, or 3 and 4, you hardly ever see a failure there.  And then add in the fact that the front of the head is fastened not only to the block, but to the front cover, which is also bolted to the block, and then you start to get an understanding of why 3 and 4 is the most common failure point.  If head fatigue and flatness was the root cause, then these engines would to me seem more prone to fail between 2 and 3.

A fatigued deck face should also mean cracks and coolant and oil leaks, and I have just never seen this unless the engine was over bored and pressed much harder than it was designed for.  In this case, expecting an output of 150HP with a KA24E head, I don't think that would be pushing it far enough to worry about.  And, you could always use head studs and a copper gasket if sealing was an issue.

Maybe different years had issues, I don't know.  But I put 145,000 road miles on a Z24, then raced it for many years.  I then had the motor sonic tested and maged before rebuild, and there were no problems.  And most builders prefer a well seasoned block, one that's been through a lot of temperature cycling, and has normalized to reduce the internal stresses from the original casting and machining.

If they were good running engines, they weren't really junk.  They were only junk if you planned on using them for an application where you were expecting to increase the power output significantly, and we're boring over factory specifications.  Just because they have a few issues, doesn't mean they're junk.  When you're putting a ton of money in to an engine to modify it, you want the best block you can find to start with.  However, if you're not throwing a ton of money into a motor, and not expecting to push it really hard, then a perfect block isn't really necessary.  Less money invested, is less money at risk if there should be a failure...

So, slapping some KA pistons in a Z24 block, and bolting on a KA24E head, isn't a lot invested.  As far as HP per $ invested, it's a pretty good ratio.  Nothing ventured, nothing gained.

I think a couple of members here have done the LZ motor, but the only one I remember by name was Cowboy Bales on the old MSN group???  I think he lived down south, Louisiana.  He had one for sale at one time, reasonable price too.  It was the high compression "peanut" head, I forget the casting number.  I think he said it put out over 200HP, he used it in mini-stock racing.

Yep, found an old email from him, his name is Mike Bales, and one of the last things he wrote, is below.  So, if anyone wants to talk to someone who's done it, that looked like an open invite! Keep in mind that email was from 2002 lol...

Good luck this year, send the guys with the L and Z series questions and modifications
my way. Hm: 985-882-7764 after 7pm cst or 504-415-6781

Mike (Cowboy) Bales
Cowboy Racing Inc.
Lacombe, Louisiana
Sealik just finished putting dual side drafts on to his LZ23.... Would love to know what hp thats putting out n go for a ride to see how well it actually does. Looks pretty awesome, thats for sure.

Byron from the 510 Realm built an LZ22 with an unknown cam in the L head he used. He also had side draft Webers or Mikuni's. The next year he got his EFI perfected and it made only 6 more hp so I would say the carbs were dialed in pretty good. Here's the dyno sheet for the EFI, just remember the carbs were about 6 hp less. (RWHP measured)

Where is Doug, miss that guy, sure hope he's ok...

Those are some good numbers there.  Any idea what compression ratio it ended up at?  I've never got a handle on how much drive train loss you get to the rear wheels though on these trucks, 2wd or 4wd...  It sure would be good to know.  I wouldn't be surprised though if this engine was somewhere near 180-190HP at the crank if it was a 4wd.

Properly sized and tuned side drafts are pretty darn near as good as EFI, that I agree with.  Getting the correct size, and get them tuned in is the hard part.  The side drafts just aren't capable of adapting to external changes, altitude, temperature or atmospheric (weather).  This is where EFI and an engine management system shine IMHO.

Ahhh, well I guess a 510 wouldn't be 4wd lol...  Well I'm getting hungry, time for more toasted oats...





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