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HybridZ

L24 to L28 Swap


HT240

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Threw a rod through the block in my L24. Picked up an L28 with a brain. Not sure if I should swap the heads and carbs from the 2.4 to the 2.8? or buy and ECU(megasquirt or other) Ive gotten used to how the carbs work, and adjusting them when needed. But not to keen on how EFI and how they quite work. But ive heard its better to stay with the fuel injected intake because its more "dependable in the long run. Also, what kind of power and mpg increase/decrease, and cost am I possible looking at? Pretty new to Zs and how they work, but I kinda want some advice on this before I make a decision. I do all the work myself pretty much. Ill post pics later.

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The only way to make a good decision is to understand what you're choosing between. In this case, search is your friend. Understand how an engine works, read up on carbs, read up on EFI and then make the decision. By "read up" I don't mean glance at something for 10 seconds, but thoroughly study what you're getting yourself into.

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The only way to make a good decision is to understand what you're choosing between. In this case, search is your friend. Understand how an engine works, read up on carbs, read up on EFI and then make the decision. By "read up" I don't mean glance at something for 10 seconds, but thoroughly study what you're getting yourself into.

 

+1

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Yep, it really just depends. If you are comfortable with carbs, it's probably easier to hook up the carbs and avoid running a new harness/ drilling the firewall... The stock EFI is good if you want a stock setup and don't plan on doing anything wild in the future. Megasquirt would be superior for power and economy and allows for pretty much any mod you would plan on doing. The L28 will have a little more torque, probably about the same economy. I'm pretty sure you can use the carb manifold on the L28 head.

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Throw the carbs on and get it running. Then research what you want to do for induction. Personally I recommend fuel injection in the long run. It's nice to turn the key and drive -no choke!! I've had both early s30 and s130 and after driving the s130 I won't go back to carbs. BUT-like the post above states- research,research,research. My two cents.

Edited by macambra
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If cost is any concern, just run the carbs. But macambra's advice is wonderful. Get it running with what you have, and then do research on EFI.

 

MS-1 build at home + wideband can be done under $500 easy. Buying a prebuilt MS-2 3.57 board + relay board + wideband + sensors + throttle body and other general "while I'm at it" stuff can run up over $1k. By contrast though, most other ECU's START at $1k and you still have a lot of work to do... MS really is that awesome.

 

MS cost also doesn't look that scary when you look at the cost of getting a really nice tripples setup with all new parts. But, you already have working carbs, which means you could be avoiding this cost all together.

 

Regarding what head to use... well what motor is this L28, and what head is on the L24? The L28 could have flat or dished pistons which really affects any choice.

 

You can throw carbs on an injected head, but most people recommend filling the injector cutouts on the intake port of the head, but it's really not a huge deal to just leave them there as a mild low pressure area. Unless you're shooting for 200+ hp who cares? Just putting your exact setup on a L28 longblock will give you a solid 15% increase in power once you get the carbs adjusted. And the beauty is that the torque increase should be seen everywhere, not just on top or on the bottom.

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The L24 was a P30/E88. The L28 is a F54/P79. Cant seem to find out if Id be able to used the L28's exhaust manifold with the carbs or use the L24's. Guess I either keep it EFI and pick-up at MS ECU, or get a valve job done on the crusty E88. ..Or find a N42 head which has holes for both the carbureted and injected manifold. ...hmmmm

Edited by HT240
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I think that the F54 might have carb manifold mounting holes. Look around for a picture. Might even show them in the FSM drawings. The L28 exhaust manifold would be missing the air injection holes, if you needed them, but should bolt on. The F54/P79 combination is flat-tops with 8.8 (FSM numbers). I don't know much about carbs, but the only real downside would probably be choking off the high RPM power with L24 size carbs, plus some tuning probably required for the L28 needs. No expert though...

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I think that the F54 might have carb manifold mounting holes. Look around for a picture. Might even show them in the FSM drawings. The L28 exhaust manifold would be missing the air injection holes, if you needed them, but should bolt on. The F54/P79 combination is flat-tops with 8.8 (FSM numbers). I don't know much about carbs, but the only real downside would probably be choking off the high RPM power with L24 size carbs, plus some tuning probably required for the L28 needs. No expert though...

 

 

The carbs fit on a p79 head, and yes the L28 exhaust manifold is missing the air injection holes. However the P79 head doesnt have the holes for air injection. Took the L28 apart a couple hours ago to see for myself.

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I'd be more worried about getting an EFI manifold to flow well at high RPM than getting L24 carbs to work well on a L28. The stock EFI manifolds are horribly undersized and become a major choking point beyond 5000 rpm.

 

Sorting out exhaust on the L28 is also easier than sorting out converting to EFI. Some basics you'll need to figure out:

 

Fuel pump (usually $200 new for a good one)

Fuel Return line (not expensive, but time consuming)

Fuel Filter (another nickle and dime in the bucket)

 

If you don't have them currently or the ones you have are iffy:

Fuel injectors

Fuel Rail

Fuel pressure regulator (commonly out of spec)

AFM (or other air metering sensors if you go MS)

AFM mounting (since your car is a 240Z you don't have that bracket, one more thing to figure out)

O2 sensor

 

To sort out all these changes could take some time, definitely consider this when making your decision. It might seem confusing to figure out how to carb the L28, but trust me when I say that's a much smaller mountain than converting a carbed car to EFI. Both are totally doable and obviously anyone swapping a non-stock motor has considered these things and had to come up with solutions.

 

Regarding the parts you have: You do indeed have flat tops if the motor is stock, and if you trust the E88 head there's no reason you couldn't use it. Your compression would be in the mid 9's, opposed to the mid/high 8's the P79 gives you. I'd suggest running a little bit more cam if you do that though. The P79 will take some minor work to get carbs working on, but plenty have done it. If you want to use the mechanical fuel pump on the E88 you'll need to do some basic machine work (doable with a basic grinder and a tap and die set). You could just use an electronic pump up at the engine though instead.

 

So you have options, none of them being bad options if you do your homework and pay attention to the detail when it comes time to work on the car. I've seen 300hp carb'ed NA motors, and 300hp EFI NA motors. I'm personally among the crowd that prefers EFI, but at the same time I also believe in the path of least resistance in order to actually DRIVE your car, not let it live on jackstands.

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