280Z Fuel Injection to Carb Swap

[Randalla]

Wondering what, if any, issues I may have with this swap electrically. I've done this many times for 240Zs I've owned, but am unsure what other functions the ECU manages on a 280Z that I'll have to work around. I plan to manage fuel pressure with an inline regulator to compensate for the difference from 3-5 lbs. (carbs) to +30 lbs. (injection). Thanks for your help/thoughts. 

[siteunseen]

He goes from efi to SUs here...

 

[SteveJ]

Fuel pump power. What year is the 280Z?

[Av8ferg]

I have a nice set of SUs that I’ve been considering putting in my 77 and dumping the EFI. Why? Maybe because I’m crazy. I must be because my engine purrs with the EFI. Only a sick bastard would fix something that isn’t broken. The idea of carbs appeals to me for some reason. A person on this forum I highly respect told me I’d be making a mistake and making my car less reliable and less easy to own and use. I’d love to see how this works out.

[siteunseen]

54 minutes ago, Av8ferg said:

I have a nice set of SUs that I’ve been considering putting in my 77 and dumping the EFI. Why? Maybe because I’m crazy. I must be because my engine purrs with the EFI. Only a sick bastard would fix something that isn’t broken. The idea of carbs appeals to me for some reason. A person on this forum I highly respect told me I’d be making a mistake and making my car less reliable and less easy to own and use. I’d love to see how this works out.

Join our club. Put those SUs on a 240.

I don't think my stock efi supplies the fuel when it could. It seems like a bottleneck compared to the carbs. The carbs get in the redline and won't stop until you decide. Efi seems to have a governor built in somehow with all the components. I'm talking stock stuff, no work arounds. On newer cars and bikes you have to re configure the ecu to get all the juice squeezed out.

[Av8ferg]

Mine revs pretty nicely.   

[Randalla]

The 280Z we are converting is a 1975. I've always been a huge SU fan and though some may make a case they are not as dependable, I've not actually found that to be the case. In fact when something needs to be addressed on the induction side, I'd much prefer the simpler diagnosing and repairs of SU's. When set up properly you can forget them for the most part. The pluses are they sound great, tip-in response is more lively, and the car is much more fun to drive. Admittedly, I'm biased having, owned over 20 early Z's with L-series engines and worked on countless others. Long live the SU's! 

[SteveJ]

Jumper these two wires together by using an inertia switch. Mount the switch securely to the dash. That will provide power to the fuel pump at key ON. The switch should cut power if you have an accident.

I think the 6 pin connector is different from the one sold at Vintage Connections. I used some that I purchase on Mouser.com. Sorry, part number for the connector isn't readily available.

If you want to get an non-generic inertia switch, you could get this: https://www.rockauto.com/en/moreinfo.php?pk=3970509&cc=1427576&pt=10756 and pair it with this connector: https://www.clipsandfasteners.com/Inertia-Fuel-Shut-Off-Switch-Harness-Connector-p/a23180.htm?gad_source=1&gclid=CjwKCAjwz42xBhB9EiwA48pT73NwDLlIv8yJGuM8TKHISt7fAUw23HCsEvFF2M9k7Fhdvmvwe0MfPhoCoIgQAvD_BwE

You would want to fashion a bracket for it, though. Since it has normally open and normally closed contacts, you could wire it to a light to tell you if you need to reset the switch if it has been activated.

[Randalla]

Steve,

Good point on the inertia switch. Now thinking of going back to a mechanical fuel pump to avoid the need for an inertia switch and assuring lower fuel delivery pressure without a regulator. Thanks for the reminder. 

[SteveJ]

2 minutes ago, Randalla said:

Steve,

Good point on the inertia switch. Now thinking of going back to a mechanical fuel pump to avoid the need for an inertia switch and assuring lower fuel delivery pressure without a regulator. Thanks for the reminder. 

Are you swapping in a 240Z or 260Z engine? If not, you have to open up the window in the head for the mechanical fuel pump, and you'll probably need to source and install the eccentric for the fuel pump. And let's not discuss the poor quality of aftermarket mechanical fuel pumps.

[siteunseen]

If it's a '75 it should have an n42 head with the pump hole already there, at least mine does.

[w3wilkes]

Rather than the high pressure pump why not go with a low pressure pump. I did this one back in 2017 and it's working fine with my SU's.

Motorsport Auto - The Z Store - K&N Electric Fuel Pump for Carbureted Z/ZX

It's not the quietest but once the car is started I can't hear it over the exhaust and my exhaust isn't that loud. I use a magnaflow 10426 resonator with a magnaflow 13216 muffler, ceramic coated 6 to 1 header w/2.5" pipe all the way back.

SU reliability issues... All I can say is bunk.