280z L28 Rebuild, Power Questions

[Ownallday]

Hello, I am currently in the process of rebuilding my second L28 for a 280z. The goal is to have a fun street car that will be plenty fun in the canyons but also have adequate power for California roads and be reliable for long distance drives. The engine is pretty much going to be a stock N42 block rebuild and N47 head rebuild with the stock intake manifold and fuel injection system along with a lightweight flywheel and Electric fans to delete the clutch fan. I know power gain wise with the stock EFI is limited but I have a couple questions regarding if any of these modifications are worth it or will make any difference.

1: Will a thinner head gasket to help increase compression make any difference with stock EFI? I already have a 0.8mm gasket that was going to go on another engine but not anymore.

2: Is there any benefit to upgrading to a 280zx Distributor over the 280z unit.

3: Is there any benefit to using an MSD 6AL ignition system with the stock EFI or in combination with the 280zx Dizzy?

4: Does a header and intake make any power difference on the stock EFI?

5: Will an adjustable fuel pressure regulator add any beneficial power?

6: I know headers and intake wont pass but will an aftermarket fuel rail pass smog in California?

7: (I know won't pass smog) Does deleting the EGR really have any beneficial power gains?

8. Will the stage 1 or 2 cam on MSA's website give any decent power gains and work with the stock EFI and can you pass smog with either?

9: Is a Port and Polish worth it?

10: Are there any modifications I missed that could potentially increase power with the stock EFI and can they pass smog aside from shorter gear ration trans and diff and weight savings?

The reason I ask the smog related questions is because I need the car to pass once or twice in California but eventually wont need to worry about that anymore if I end up moving but would still like to keep the stock EFI on this specific build in the future too. Thank you to all for the responses and help!

[SteveJ]

Headers and EGR delete won't pass the visual inspection. Your car could put out zero CO2, NOx, CO, and HC, but if it doesn't have all of the smog equipment that Nissan installed or CARB equivalents, that's likely a non-starter.

[Ownallday]

32 minutes ago, SteveJ said:

Headers and EGR delete won't pass the visual inspection. Your car could put out zero CO2, NOx, CO, and HC, but if it doesn't have all of the smog equipment that Nissan installed or CARB equivalents, that's likely a non-starter.

I am aware of that, I am asking for when the vehicle will be smog exempt out of California. Will an aftermarket fuel rail pass visual?

[Zed Head]

2 hours ago, Ownallday said:

The reason I ask the smog related questions is because I need the car to pass once or twice in California

 

57 minutes ago, SteveJ said:

Headers and EGR delete won't pass the visual inspection.

 

Your question specifically said California.

https://asktheref.org/Services/Smog-Check-Results-Review/

 

Why did my vehicle fail the smog inspection?

Vehicles can fail a Smog Check for any number of reasons, some common reasons for failing a smog check include:

• Excessive tailpipe emissions
• Modified with non-approved parts or computer programing 
• Check Engine light or OBD monitor failures
• Faulty sensors or computer controls
• Vacuum leaks
• Other

Edited January 28, 2023 by Zed Head

[Reptoid Overlords]

If you're tearing down the bottom end you could replace your dish top Pistons with ZX flat tops for more compression and leave the stock EFI and stock cam.

I believe it is getting difficult to find oversized pistons, but if your bores are within spec, you might still be able to get the stock size flat tops.

[Ownallday]

18 minutes ago, Zed Head said:

 

 

Your question specifically said California.

https://asktheref.org/Services/Smog-Check-Results-Review/

 

Why did my vehicle fail the smog inspection?

Vehicles can fail a Smog Check for any number of reasons, some common reasons for failing a smog check include:

• Excessive tailpipe emissions
• Modified with non-approved parts or computer programing 
• Check Engine light or OBD monitor failures
• Faulty sensors or computer controls
• Vacuum leaks
• Other

Yes, mods like headers, intake, egr delete I know will fail visual inspection. I am not worried about that now as I know to leave those on for when I get the car smogged. I will however decide to remove or swap them out in the future when the car will no longer require smog checks outside of California if any of them can benefit from any power increase. Things like the cam and fuel rail I am uncertain if those will pass smog as I'd like to do them while everything is torn apart already and the current stock fuel rail I have is surprisingly cracked and leaking.

26 minutes ago, Reptoid Overlords said:

If you're tearing down the bottom end you could replace your dish top Pistons with ZX flat tops for more compression and leave the stock EFI and stock cam.

I believe it is getting difficult to find oversized pistons, but if your bores are within spec, you might still be able to get the stock size flat tops.

Bottom end is torn apart already, however I have brand dished pistons already and haven't been able to find standard size flattops. Would the insane amount of extra compression work with a stock 280z Fuel Injection system and computer and gain power though?

[siteunseen]

Best bang for the buck and not worry about sniffer test is an aluminum flywheel. You can buy one or have the OE lightened as much as possible. I got lucky and bought a 240 project with an 11 pound  Tifton or Tilton?? but Findaza still makes them I think.

My car revs like a motorcycle. With the header and performance exhaust it sounds like a Ferrari screaming bloody murder.

 

[Ownallday]

11 minutes ago, siteunseen said:

Best bang for the buck and not worry about sniffer test is an aluminum flywheel. You can buy one or have the OE lightened as much as possible. I got lucky and bought a 240 project with an 11 pound  Tifton or Tilton?? but Findaza still makes them I think.

My car revs like a motorcycle. With the header and performance exhaust it sounds like a Ferrari screaming bloody murder.

 

Already ahead of you, have a Fidanza Lightweight flywheel ready to be put on. Was the first thing I bought for the build as my other Z also has this flywheel and made a huge difference with my triple weber Z.

[Reptoid Overlords]

23 minutes ago, Ownallday said:

Bottom end is torn apart already, however I have brand dished pistons already and haven't been able to find standard size flattops. Would the insane amount of extra compression work with a stock 280z Fuel Injection system and computer and gain power though?

I have built an F54/P79 with a shaved head and left the stock cam and stock EFI.  It definitely made more power.  The problem was even with 92 octane fuel it still had detonation.  And that head is designed to combat detonation.    Different motor combo but the same effect on compression.  You'll have to be aware of detonation. Is California premium fuel 91 octane?   I would add octane booster to the fuel and it would stop the detonation, but leave this orange crap all over the combustion chamber.  Ended up sending another unmolested F54/P79 to Datsun Spirit in Northern VA. because I can't build a motor like those guys haha. 

So yes..It makes more power with the stock cam and stock EFI.  It will detonate without octane booster. 

Edited January 28, 2023 by Reptoid Overlords

[Ownallday]

14 minutes ago, Reptoid Overlords said:

I have built an F54/P79 with a shaved head and left the stock cam and stock EFI.  It definitely made more power.  The problem was even with 92 octane fuel it still had detonation.  And that head is designed to combat detonation.    Different motor combo but the same effect on compression.  You'll have to be aware of detonation. Is California premium fuel 91 octane?   I would add octane booster to the fuel and it would stop the detonation, but leave this orange crap all over the combustion chamber.  Ended up sending another unmolested F54/P79 to Datsun Spirit in Northern VA. because I can't build a motor like those guys haha. 

So yes..It makes more power with the stock cam and stock EFI.  It will detonate without octane booster. 

Thanks for the insight and good to know. I may considering having the machine shop mill the head. But I would like to avoid having to put anything more than 91 octane which is the most we get in California. There is race gas where I live but $10 a gallon.... Naaa.

[Reptoid Overlords]

Part of my problem with that setup wasn't necessarily that it was a bad deal for pump gas,  It's that the I never did mess with reworking the vacuum advance so that it wouldn't advance to stock specs and cause detonation.   Later I found that the distributor had developed the typical broken bearing cage problem.  I left it alone and eventually bought the 123 distributor since I got the DSI motor.

So you could still use flat tops, if you could find them.  And you could either mess around with re working the vacuum advance on the distributor or get the 123 distributor.  It's spendy, but it lets you tune it how you want it without any guesswork. 

https://www.classiczcars.com/forums/topic/31615-280zx-distributor-advance-curve-reference/?&page=2#comments

Post #33 from Chickenman begins to explain a bit about it.

Edited January 28, 2023 by Reptoid Overlords

[Ownallday]

15 minutes ago, Reptoid Overlords said:

Part of my problem with that setup wasn't necessarily that it was a bad deal for pump gas,  It's that the I never did mess with reworking the vacuum advance so that it wouldn't advance to stock specs and cause detonation.   Later I found that the distributor had developed the typical broken bearing cage problem.  I left it alone and eventually bought the 123 distributor since I got the DSI motor.

So you could still use flat tops, if you could find them.  And you could either mess around with re working the vacuum advance on the distributor or get the 123 distributor.  It's spendy, but it lets you tune it how you want it without any guesswork. 

Ah okay I see. Finding them is the big problem as they are usually never on sale new or used without having to go bigger which I dont want to do. My curiosity is would I be able to pass smog initially with such a huge compression bump?