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carb change over from FI


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Ok .. I have asked before .. but it is time for me to change this crappy FI system out and install my SU's. Can anyone run down the parts I will need to change my 77 280 over to SU's.

I know I will need to install a fuel pump. I am going to use an electric pump.

I am going to contact ZTherapy and am considering their carb exchange.

Other input on this subject would be great. BTW I am doing this cause I am having electical fault with the sytem now and I dont want to put time and money into the FI system cause I think it is crap anyway.

Cheers ..bruce

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Ok, this is an easy one.

Get the carbs. intake, and linkage from any source. Unbolt the FI. Bolt on the carbs. install a pressure regulator, set to 4lbs. Go and have fun. This is all that I did when I installed an L28 in my 240. I don't think there is anything I left off. This is also all that a friend and I did when he converted his 76 280.

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Yeah, the basics are pretty simple. But there's a lot of details to getting it done right.

  • A fuel pressure regulator is a viable option, if your existing pump is good. But you don't want a cheap regulator that might go bad and start delivering 30 psi to your SUs. The best scenario in that case would be a rich or flooded engine. The worst is a catastrophic engine fire! Better to have a cheap low pressure pump that can't over pressurize. I found one locally that is 4.5 psi for $30 US.
  • Your injection probably has coolant lines running to the manifold and/or throttle body. You may or may not want to connect them to your SU manifolds, depending on your climate. But you'll have to deal with them either way. Either re-plumb them to the manifolds, re-route them or block them off. (I'm blocking mine off.)
  • If your car has an oxygen sensor of EGR in the manifold, you'll have to deal with that as well. The oxygen sensor can be left in place, or you can get a plug for its hole. The EGR (if any) will have to be plugged somehow.
  • You'll need different bolts (or better, studs and nuts) for the intake manifolds. The injection manifold bolts into different holes on the head. Luckily, the holes you need are still there, under the current manifold. The studs or bolts need to be 8mm x 1.25. If you use studs, 40-45mm long is good.
  • You will need to re-route the breather hose from the valve cover, as well as the PCV hose. You will probably need new hoses for those. PCV should go into the balance tube on the manifolds, the breather goes into the air cleaner.
  • You will have to fabricate a choke cable setup. I've got it much easier here, I just need to find and re-install parts that my car originally came with. You will need to start from scratch.
  • The vacuum advance needs to go the fitting on the front carb. In my case, my ignition is partially controlled by the injection brain, so I will need to deal with that as well. I don't think yours is that way, however.
  • I'm not sure about your car, but in my car with the ZX injection there is a slight mismatch with the throttle linkage. The carb linkage won't quite let the injection fall all the way to idle - it holds the throttle open ever so slightly. So to make certain that you are able to open the throttle fully, you may want to get the linkage pieces from the firewall of a carb'd car too.
  • Basic parts list - one pair round-top SUs, center linkage, pair of manifolds (including the balance tube with linkage), heat shield, return springs, fuel pump or regulator, fuel rail, air cleaner(s), choke cable assembly, manifold gasket, 8mm x 1.25 bolts or studs, assorted metric fittings and plugs, fuel, vacuum and coolant hoses, etc.

Last thought - my car didn't come from the factory with injection, it was (rather ham-fistedly) installed a few years back with the '83 280ZX engine now in the car. The installation was not done right, and so rather than start over I'm going to yank it and go back to carbs.

But had it been done right, or if I had a car that had come with it from the factory, I'd probably fix it rather than replace it. When it's in good shape, there's nothing wrong with the factory injection for a daily driver.

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Hey arne, just a quick note--be sure you put the vents in the hatch that your rig is supposed to have--without it, you have no way to release pressure in the cabin (under perfect rubber-sealing conditions)....I would think you can put the vents in yourself; I've heard the plastic covers are a pain to find however....I got a 72 so I don't have that issue or experience with it...but I do know you need those vents for ventilation.

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Hey Arne,

Your information is all correct and much more detailed than I provided. I did my L28 maybe 10-11 years ago and have had no issues. Mine was maybe as easy as it was since I started with a 240 and not a 280. But as I stated it was a very simple conversion just more detailed than I remember. Thanks for the refresher course. My son and I are about to start on rebuilding a 280 as his first car. I plan on going with carbs rather than the FI. I like the look and simplicity that carbs provide. I'll be sure to look up this thread when we get to that point in our build.

Barrie

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Hey arne, just a quick note--be sure you put the vents in the hatch that your rig is supposed to have--without it, you have no way to release pressure in the cabin (under perfect rubber-sealing conditions)....I would think you can put the vents in yourself; I've heard the plastic covers are a pain to find however....I got a 72 so I don't have that issue or experience with it...but I do know you need those vents for ventilation.

I plan on it, Dave. The hatch on my car is not so great, so I'll probably try to find an original vented one, rather than add vents to this one.

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  • 2 weeks later...

My car has SUs again, and surprisingly, it runs!

Spent pretty much all day doing it, but it was a success, pretty much. Removed all the injection and replaced it with SUs. Had to make two trips to the parts store during the job to get unforeseen items, but all in all it went quite smoothly.

The surprise was in how well it runs - I did nothing to my carbs, and I have not a clue how they are set up. Just bolted them on and trusted that they would be close enough, and they are for now. Later I will have to fine tune them.

Still a few bugs to work out, but they are more with the ignition than the carbs. My tach now works, but reads obviously low. And the engine won't shut off when I turn off the key, I have to get out and pull the wire from the coil. I'm pretty sure those two problems are related, as when I turn off the key the tach starts reading much higher. Got a bug in the wiring somewhere.

P.S. - Dave, I picked up a vented hatch yesterday too!

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ha ..I just finished mine too ... well almost. I found a badly cracked manifold so my header went on .. without any pipe or muffler so I need to get it to a muffler shop. I need to find some bolts for the air cleaner that the wing bolts thread into to bolt the air cleaner on, I need to get a PCV hose, I need a heat shield .. but the car seems to run great. I rebuilt the carbies with Z therapy kit. I was dissapointed to find they dont supply the gosse jets (sp?) anymore. The video goes on about how much better these jets are than the originals ..and I find the originals in the kit. I also found the video to be abit wrong .. the carbs I have have a long and a short pivot point (ears) and you must set the float different for each one or else one carb will not get fuel. But all in all a very succesfull project. It is all downhill from here.!!!!

BTW .. I have a good FI system for sale ... any takers ?? I found the electrical problem was with the power supply and there was never anything wrong with the FI at all !!! My fuel pump was shutting off due to a power interuption.

Cheers ..Bruce

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Hey guys,

Against all myths the vent covers for series I 240 rear hatches are available at your local Nissan dealer. Part number 90950-E4101 pick mine up yesterday. BTW less than on Ebay

I suspected as much. I think that a whole lot of the new parts on eBay are simply ordered from the dealer (or other supplier) and then resold at a higher price. For example I noticed that '70-71 choke knobs open for $8.50 plus shipping on eBay, yet the same knob is $5.45 from MSA.
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I am looking for a choke cable for my 280z I cant seem to find a cable that will adapt to the 72' SUs I have just installed. Can anyone shed some light on this. Is there a chance I will find the correct assembly that will bolt onto my 77' 280 console?

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Gator,

You might PM one of our Aussie friends and see if they have some info on your choke cable. You also might post a photo of the console with the area uncovered and we'll see how close it is to a '73-74. BTW, the '73 choke cable is still available from Nissan. Good luck!

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<snip> the engine won't shut off when I turn off the key, I have to get out and pull the wire from the coil. I'm pretty sure those two problems are related, as when I turn off the key the tach starts reading much higher. Got a bug in the wiring somewhere.

P.S. - Dave, I picked up a vented hatch yesterday too!

Arne, you might give Beandip a PM. Seems he was telling me that scenario the other day. I thought he was saying something about putting a diode in the system to solve that problem. Best of luck to you and thanks for the updates. It is really good info. Beandip just helped me (more like taught me and helped me) pull the motor and tranny from an '82 and I'll be doing much the same this winter or spring.

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Fired it up again today, and ran it for a short while. It's running quite rich, I'm probably going to have to reset everything and start from scratch. But the simplicity of the SUs will make that much simpler than trying to deal with a botched injection installation. Very happy with it so far.

And to recap, my earlier long post about what was needed was pretty accurate. I apparently had all the issues identified before I started.

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