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KA24E Swap into a 1986 720 4x4 Questions


MaxChlan

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As those on the forum may know, I have a 1986 720 4x4 with the carbureted Z24 engine. As it stands, my Z24 runs fairly well. If you've read my thread, my truck does not have the fast idle cam screw, so it is pretty cold blooded. The Hitachi is not the best carburetor in the world, but once it's warm I do not have any issues. In addition, oil seems to disappear from the engine, but not at an alarming rate. I check it every time I fill up, and I put 1/4 or 1/2 a quart every four or five fill ups depending on how much I am driving. As of right now, it is not a concern. Looking into the future, I see myself having this truck for some time as I have grown fond of the bumpy ride and the people coming up to me at the local Holiday saying that their dad/brother/uncle had a truck just like mine, and how they loved it. With this in mind, I have a few questions regarding the Z24:

 

  1. What is the life expectancy? 200,000? 300,000?
  2. What starts to go wrong, and what types of preventative maintenance can I do other than retorquing the head bolts to prevent head gasket failure? 
  3. When should I just replace the head gasket?

If the outlook looks good, I would like to keep the Z24 in for as long as possible. With this in mind, I am also afraid that I might get tired of the cold-bloodedness and the somewhat underpowered nature, and also the potential lack of parts or issues with the Z24 down the road, which brings me to the topic of this thread.

 

The actual swapping of the engine does not seem like that big of a commotion. From the research I have done, I have learned that KA's bolt right to the FS5W71B (short shaft) transmission in the 720 with an ECU, higher pressure fuel pump, and some fabbing of engine mounts. What does concern me however is the long term viability to driveability of the truck, and if swapping is right for me. Budget aside, I have quite a few questions:

  1. For those who have swapped into 4x4 trucks, have you noticed better daily driving? (Better MPG, quieter, more power, or whatever you think makes a good daily)
  2. What is the definitive maximum crank or wheel horsepower the FS5W71B transmission and other driveline components can take on a 4x4?
  3. If I were to swap, what would be on my checklist?
  4. What are some things to watch out for while I have the engine out of the truck? Any other to-dos?
  5. Lastly, is it worth the time, money, and effort?

Like I said, this is not a pressing issue. I am not being forced to make a decision. This is mostly for getting an idea, checking things out, and potentially ordering parts months or years in advance so that when the Z24 decides to go, I have the things I need to keep this 720 on the road. 

 

 

 

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I am a big fan of the Z24 myself. Others will encourage you to swap it out. It comes down to a personal preference, I suppose. I think Z24 parts will be available for rebuilds for a while yet. My machinist got a new head for me from a casting company in Aussie that makes new replacements. An engine rebuild kit is pretty reasonable still. I zero times my Z24, using a local machine shop for the machining, added a bunch of little extras, and didn‘t quite spend $1,500 altogether doing it myself. That‘s pretty cheap for a brand new motor.

 

Is it burning oil or leaking it? How many miles on the odo again?

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  • What is the life expectancy? 200,000? 300,000? yes

  •  What starts to go wrong, and what types of preventative maintenance can I do other than retorquing the head bolts to prevent head gasket failure? Maintenance! Change engine oil and filter on time, transmission, trans case and differential oil every 30K, set valve lash and do tune ups.

 When should I just replace the head gasket? If and when the gasket blows.

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What is the definitive maximum crank or wheel horsepower the FS5W71B transmission and other driveline components can take on a 4x4? The FS5W71B was used on the non turbo 280zx so whatever that engine made... 150hp???

If I were to swap, what would be on my checklist?

What are some things to watch out for while I have the engine out of the truck? Any other to-dos? If replacing it what's there to look out for?

Lastly, is it worth the time, money, and effort? If your Z24 needs replacing or you want more power, yes

 

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Run it as is and slowly collect parts for a ka swap in the future. Finding everything takes time. It is a little bigger deal than some on here let on. The bag components bolt up but there are a lot of small details that are a pain. There is also a lot of nickel and dimes that add up quick and you need a good selection of tools and at least access to a welder.

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For one the Hardbody KA is the best bet. It's lighter and is already a truck engine so there is a 4x4 oil pan that is closer to clearing the front differential than a 240sx pan which has to be heavily modified. The truck intake will support a down draft carb also.

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The oil pan is not close enough. The naps pan has to be grafted to ka pan. Clearances are less than half inch. There is no way a 240 ka would work in a 4x4 unless SAS first. Mike can you site a running example with the truck manifold with a downdraft? Those long drooping runners would no be good for a carb application. Nissan did make a,ka24e downdraft manifold on the KAs motor offered south of the border but I was never able to source one. The fuel injection starts so fast and no cold nature issues so I am glad to ditch the weber.

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What is the definitive maximum crank or wheel horsepower the FS5W71B transmission and other driveline components can take on a 4x4? The FS5W71B was used on the non turbo 280zx so whatever that engine made... 150hp???

 

 

Technically, transmissions are rated for a torque figure. Mike, if im wrong just correct me, but iirc the FS5W71B is rated for 215ft/lbs, but there are a few people running more than that on theirs with no current issues.

 

The oil pan is not close enough. The naps pan has to be grafted to ka pan. Clearances are less than half inch. There is no way a 240 ka would work in a 4x4 unless SAS first. Mike can you site a running example with the truck manifold with a downdraft? Those long drooping runners would no be good for a carb application. Nissan did make a,ka24e downdraft manifold on the KAs motor offered south of the border but I was never able to source one. The fuel injection starts so fast and no cold nature issues so I am glad to ditch the weber.

Oh no he didn't! jkjk.

 

Find 'Farmer Joe' profile. KA24DE with 38/38 weber and EI distributor.

^^^^ +1 Farmer Joe

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Mike I over studied this for a long time and had read farmers post. The 32/36 seems to have had so many issues he gave up and tried the 38/38. One post about how it ran so much better but that was it. No more follow up. It looked like his next engine was FI Not wanting to argue, just I didn't want to invest in what looked like an experiment and went the proven route with the 240sx intake and all went well.

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Technically, transmissions are rated for a torque figure. Mike, if im wrong just correct me, but iirc the FS5W71B is rated for 215ft/lbs, but there are a few people running more than that on theirs with no current issues.

 

 

 

Yes torque is a better value but many equate HP handling. I know Nissan did not trust the zx turbo with the 71B and went with the T5. For want of a better torque value, 215 sounds about right. You can always exceed the max limit but....? Probably better to have something stronger than what you need. A 71C would fit the bill. ZX owners who lunched their T5s swapped the non turbo 71C in and had no problems. 

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