1972 240 carb to fuel injection conversion?

[Shoottathril200]

I just recently decided to start working on a 1972 240z that I acquired in a trade several years ago. It has two Weber two barrel carb setup that somebody before installed and did a rather poor job and would take too much time and effort into straightening out the mess (linkage butchered, air injection(?) tubes on manifold cut and crimped off, vacuum lines blocked off, etc) and since I'm not much into carbs, I was thinking of installing a fuel injection unit I found on an '81 280(?) that appears to be able to bolt up with little or no problems. This is the first 240 I've worked on and need info if this type of conversion is possible and what is needed. Also will be selling off the carbs if any one is intrested and if the fuel injection conversion is possible.

Would have posted pics but seems too complicated a set up and time consuming to post pics on one site and link from here. Rather insert pics in e-mail (much easier) than this type of board. Any help is much appreciated.

Shoottathril2000@aol.com

[Bruce Palmer]

You'll need to machine injector notches in the intake ports and from there on it's a bolt in, wire up, for the modules and harness.....

We, here at Ztherapy, see the reverse of what you are wanting to do, with owners wanting to swap out their degrading injection sytems for the simplicity of SUs.....

[Arne]

Yes, it can be done. But speaking as someone who bought a '71 240Z with injection (from an '83 280ZX) added, I have reservations as to whether that is the best answer.

First - regarding the bolt-on of the later factory injection - the cylinder heads used on Zs prior to 1975 lack the notch in the intake ports that are needed for the injectors them selves. So assuming you don't have a later head (or engine) in the car, you would need to modify the ports on the head to use the factory injection, or swap to a later injection head.

Past that, the factory injection controller gets input from several sensors throughout the engine compartment. So in addition to the obvious injection parts, you need to look into either changing out the thermostat housing for the temperature sensor, and perhaps other sensors as well.

In short, swapping to a later factory Nissan injection on a 240Z can be done, but doing it right will be an involved project. I know, as the job on my car was not done right. I went back to carbs to fix mine.

If the goal is to correct the botched Weber install, I'd recommend swapping it back to '70-72 factory dual carbs instead. Finding a complete setup including manifolds, linkages, carbs and airbox is fairly easy, and far simpler to reinstall that setup than it will be to convert to the factory injection.

If you really do want injection, I'd recommend looking into an aftermarket injection system instead of the factory system. This will be more expensive, but you may not need to change or modify the head, wiring and plumbing will be simpler, and the performance capabilities of an aftermarket system are greater than what the factory can deliver.

[Shoottathril200]

What about swapping heads and skipping over machine work for injectors? Is the injector system that bad that everyone is switching over to carb and what exactly are the drawbacks? I would hate to convert over and find power output/curve is less than carb setup and what about fuel consumption? It would seem me that since most fuel injection systems are maintenance free and less fuel consumption that this is the only way to go.

[sblake01]

I don't have a problem with the fuel injection system. My experience is with cars that had it factory installed, however. Nothing is 'maintenance free' not even Palmers vaunted ZT SU's. I just think that converting a non EFI car to the Nissan factory system would be nearly if not as expensive as going aftermarket. In which case the best and least expensive solution for you would be the SU's.

[Bruce Palmer]

I believe what the guys we hear from are talking about, is the frailty of a 20 something year old system. Degrading plastic pieces, sensors, good today, gunny bag tomorrow..... Resulting in a basic unreliability that they see as being overcome by the installation of a "new' SU setup with 3 moving parts.

Again, I'm just relating what I hear from the field.

[Arne]

Both Bruce and Stephen have their points. A well-maintained factory system can be fairly reliable. Of course, most of the systems you'll be able to find these days are not well-maintained, and will have a fair number of worn and aged parts. Converting and refurbishing an old factory system to make it reliable will likely be fairly expensive. If it is in good shape, the factory injection should probably deliver similar power to a good set of SUs. But probably not more power.

[sblake01]

I said 'vaunted' as a good thing. To each; their own. Bruce I'm on your side on this one. I made no mention of the fuel tank, pump, fuel lines, purge tank, and the rest of the laundry list of things that would go with converting an non EFI car to factory EFI. Stick with the carbs.

[Arne]

Last thought - replacing the cylinder head is not a trivial thought if you still have either a stock 2.4 or 2.6 liter block in it, as the later injection heads have larger valves and chambers. You may need to notch the block for valve clearance, and you will definitely have lower compression than now.

Again, in my opinion the simplest, cheapest and least intrusive way to go here would be to go back to early SU carbs.

[beandip]

It has two Weber two barrel carb setup that somebody before installed and did a rather poor job and would take too much time and effort into straightening out the mess (linkage butchered, air injection(?) tubes on manifold cut and crimped off, vacuum lines blocked off, etc) and since I'm not much into carbs, I was thinking of installing a fuel injection unit I found on an '81 280(?) that appears to be able to bolt up with little or no problems.

Shoottathril2000@aol.com

I have a '73 240 that I bought about 7 years ago. A PO had changed out the old flat tops and installed 4 screw SUs. Like your engine the air injection on the exhaust manifold was all blocked off and all the emissions parts removed . This engine ran great and with out a problem. I would have done the same thing my self. After driving it for a couple of years, I decided to ''redo'' the car. I pulled the engine and trans as part of the disassembly. While the car was apart I came across a '82ZX engine in good condition for a fair price. It came complete with injection, headers , even the alternator. I gave the injection intake away and used my SU set up from the L-24 engine . The engine runs strong and the performance is far and away greater than the 240 engine. I haven't seen dyno results for SUs vs OEM injection taken on the same engine. But I have been told by experienced people that the SUs will make more torque at the low end and the injection at the upper end of the RPM ranges. And that overall the difference isn't that much. Now emissions wise, this is another matter. If you make the effort to learn and understand how these simple carbs. function, you will see just how easy they are to use. Weber's this is another matter. I cannot help you in any way with them. I know of two Z Mechanics that will not work on a Z engine that is equipped with them. My 2 cts. Gary

Edited March 22, 2014 by Arne
quote repair

[Carl Beck]

The Fuel Injection System on the 280Z/280ZX's were put there by the factory to meet the US Emissions Standards. They are analog (ie hard wired) systems, and the only way to "tune" them is by feeding false signals from the sensors they use. By todays standards they are historic junk...

Making the situation even worse - call your local Nissan Dealers Parts Dept. - and price a new set of Nissan Injectors...CARZY!!!

If you feel at home with Fuel Injection Systems in todays digital world... by all means look into what is available in the aftermarket... Todays F.I. systems are very "tuneable" and a way of overcoming the limitations of the tapered metering rod's in the S.U.'s..

Visit hybridz.org and go from there... lots of guys have installed various F.I. systems on the older in-line sixes - to yield great results.

good luck,

Carl B.

[Shoottathril200]

Thanks for the input guys, learned a few new and different ideas. I did manage to find a set of SU carbs and intake that appear in good shape. I might give that a shot first just to see how they perform. Anything would be far better than the Webers that are on it now and all the butcher work that needs to be corrected to at least resemble factory.