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Paul

RB25DE, RB26 NA conversion or L28 rebuild 280z restomod

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Hi 
 
If anyone on here has previous experience or has undertaken such a project I would be grateful for their advice and help in the following.
 
I am building a street able and possibly a light competition car. Something to have fun with.
 
What I imagine is a high revving, very responsive engine with uprated brakes and suspension and a stiffened chassis. I am looking for around 180 to 200 wheel horsepower. The type of car that is not stupidly quick, but something that you can rev out and enjoy pushing through the bends and enjoy through the whole rev range. Not an all out track car with all the power at the top end.
 
I have built a few projects my self and am looking to build the engine myself. At the moment I have my 280z with the stock L28 engine with stock EFI system. I have got it running but don't like the way the engine performs. It seems to have a bit of torque but is sluggish/lazy. It is not a free revving, spirited engine. This could be because it has lost its performance as its old and has an out dated EFI system but from what I have read the L28 is a long stroke engine so not high revving and responsive. 
 
This has led me to consider, from what I can see are the 3 options. I want to keep the car naturally aspirated.
 
1. Rebuild my L28 and increase compressing as from research its a low compression motor. Also add triple Webbers and some cylinder head work (CAM etc.) I am not to hopeful as from what I can tell the L28 is a long stroke engine so even after this work it wont be high revving and will not be very responsive. Also the stock 5 speed gearbox does not seem great for this application.
 
2. Source an RB25DE as I want to keep the car naturally aspirated. From my  research these engines rev higher and make about  150 wheel horsepower. So with this engine I may get away with a simple refresh and possibly some cylinder head work, cams etc to squeeze a bit more power out of it. 

I will need new mounts, prop shaft, wiring loom etc.

 
3. Source an RB26 and turn it into a naturally aspirated engine just like Sung Kang's

 build. This seems to be the more expensive option rather than the RB25. I have done some research and it seems in order to raise the compression of the RB26 I would need to install high compression pistons and stronger rods, change the CAMS, New springs and possibly port and polish the head. I would want to produce an engine that has performance through the rev range though and not all at the top end. I will also need a wiring harness kit, new sump to fit the S30 chassis, ECU and prop shaft made. I calculated this all to cost, including the purchase of the engine and gearbox (RB25 gearbox) to be about £7k if I build it my self.
 

So if anyone has any experience in this it would be great to hear their opinion and what they have done.
 
Many thanks
Paul

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Not sure what your actual experience is with these motors are , but the L28 is capable of high revving to the limit of cast pistons . For your goals you might need to step out the box of strictly getting what you want thru HP and revs. Drivetrain changes like a better gears and a slicker trans can make huge improvements . Any engine swaps will cause a lot more work, time and frustration . Bump your compression a bit and run a bigger cam and find a way to manage it with programmable EFI or triples or even SU’s 

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18 hours ago, Paul said:
What I imagine is a high revving, very responsive engine with uprated brakes and suspension and a stiffened chassis. I am looking for around 180 to 200 wheel horsepower. The type of car that is not stupidly quick, but something that you can rev out and enjoy pushing through the bends and enjoy through the whole rev range. Not an all out track car with all the power at the top end.
 
This has led me to consider, from what I can see are the 3 options. I want to keep the car naturally aspirated.
 
1. Rebuild my L28 and increase compressing as from research its a low compression motor. Also add triple Webbers and some cylinder head work (CAM etc.) I am not to hopeful as from what I can tell the L28 is a long stroke engine so even after this work it wont be high revving and will not be very responsive. Also the stock 5 speed gearbox does not seem great for this application.

 

Hello Paul and welcome! I'm not sure where your notions regarding the L28 come from but I'd disagree. What you describe above is totally doable via "Option 1". I wouldn't consider a 79mm stroke as particularly long, you can build an L28 to happily spin to 7k RPM all day long. Balance the engine, bump the compression, put in a hearty cam, some headwork, triple carbs (or ITB's), a lightweight flywheel and you're set. 


On the topic of gearboxes, there are multiple options out there, e.g. the FS5W71B box from period Nissan/Datsuns, FS5W71C from later Nissans (240SX in the US), the T5 from the 280ZX Turbo, along with less often used boxes like the CD009.

 

I've built pretty much what you're looking for so please feel free to reference. I apologize as the information is sprinkled throughout but there's enough L-series content in there to keep you busy: https://forums.hybridz.org/topic/111062-leons-other-260z/#comments

 

There's enough great reference material here at HybridZ to keep you reading for days. The Z-Car Blog has some great inspiration as well: https://www.zcarblog.com/

Edited by Leon

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FWIW, the F20C of the Honda S2000 has an 84mm stroke and revs to 9000RPM from the factory. The F22C1 has a 90.7mm stroke with an 8200RPM limit. The pistons are forged but you get the point. ;) 

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Thanks Leon for your reply.

It is most helpful and thanks for the link to your thread showing what you have done.

 

My experience so far has only come from driving my 280z and I found the engine to be lazy and the gearbox does not feel great. 

 

Its good news to hear that it is possible to get what I imagine from the 280z engine. I will also probably change the transmission to a 200sx one as I imagine that would be a significant improvement and I will go with a triple weber setup.

 

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