z24i EFI, TBI, to weber carburetor conversion

[Frankie Pintado]

I would have bought one. I almost had one made, but I figured it out without one mostly just to get the job done faster/cheaper.

You might as well offer one for the z24 also because the ones from redline are cast, and the finish is poor; they seem to do the job though.

However, the reason that they are cast is that redline can just switch casting molds in seconds to make adapters for all sorts of cars. Who knows how many of these they particular models they actually sell. Maybe not that many.

[rico808]

hey frankie i did everything in your diagram truck will not start just rotates and rotates plugged all the vacuum lines everything.f regulator set at three psi stock fuel pump in good working order.My tbi set up was working fine before slapped this webber on.Any suggestion

[Frankie Pintado]

Fuel, spark, compression. That is all it takes my friend. Start checking spark first, then fuel, and then compression. Oh yeah, and the carburetor bowl has to fill up before it will start from being completely dry. Cycle the key a few times to crank up the fuel pump and fill the carb bowl. These things will run rich or lean. It doesn't matter, If it's not broken it will start. Squirt some carb cleaner down into the carb and try to start it. If that makes it start, then you aren't getting fuel. If you have spark, then check that the adjustment screws are about 1 1/2 turns out. If that doesn't do it, then you've got some serious problem and you should just go through the whole thing again. Test your fuel pressure, major vacuum leaks will mess you up too. You haven't given me much info here so I'm not gonna be able to help you any more than that.

So here's the update:-)

It has passed a tailpipe test.I've put another 2k miles on this puppy. As I mentioned I am in an emissions class.

Today I brought the truck in and tuned the carb with a 5 gas analyzer on an emissions dyno. The results were surprising. Just by adjusting the screws to 1 1/4 turns out, I was able to pass. No egr, No air pipe, no smog pump. No emissions equipment hooked up whatsoever. WTF??

[seang]

Naps-z has a great combusiton chamber design for emissions control. It was one of the best in the world when it was introduced.

[Frankie Pintado]

Oh yeah and it is likely that my cat is shot too. I could check if my O2 sensor works. The air pipe was rusted off of it. I welded it back on just so it was there.

[Frankie Pintado]

Oh, and on my way out of the parking lot I pulled over and turned it richer again. It runs better a little rich. Sorry trees.

[Frankie Pintado]

Naps-z has a great combusiton chamber design for emissions control. It was one of the best in the world when it was introduced.

I can certainly believe that now. And I feel like I've really stuck it to all the carburetor nay-sayers, and Weber tech support. Please tell everyone that Frankie Pintado (who is a notorious a**, and usually right) told you so.

So I get:1. Better torque2 Better horsepower3. Much better throttle response4. Better fuel economy (depending on how I drive, of course)5. Passing emissions6. Cheaper replacement parts 7. Simpler diagnostics and maintenance

What's not to like about this?

After over 12k, I'm convinced this is an excellent setup, and the best solution to replacing an obsolete TBI system.

[maurojr81]

hi im new to this forum, actually i joined because of this thread. frankie i have a quick question. the 1" peice of 1/4" hose you put on the return line, what is the purpose of doing that? i get everything else, just a little confused with that.

[markhu]

I think the little bit of smaller hose was to provide a little "resistance" for the return line.

My question is about the "stealth" part --I don't know what was hidden... There are pics, but I don't know what to look for in the picture.

Thanks for this great write-up.

[Frankie Pintado]

OK first:
You're right about the little piece of hose. The fuel will take the easiest path, which without that little piece of hose is back down the return line to the tank. It will run without it, but will start to sputter on long pulls when the carb bowl starts to go empty.

Now:
The stealth issue. Laws will vary by location, but things are pretty relaxed where I am. I am required to have a sticker on my windshield stating that my vehicle has been inspected by a state inspector. Mostly they look at brakes, tires, horn, lights and basic safety stuff. Recently this was added to the inspection: "All original Emissions equipment must be present and operational". This doesn't mean that the inspector is going to test your emissions system (on obd 2 cars it does), but they will open the hood and quickly glance in to see if you've riced it out excessively, or removed anything obvious.
Fitting the stock air filter onto the weber, and hiding the fuel pressure regulator under the manifold was enough to make it appear stock at glance and get me a sticker.

[Frankie Pintado]

Oh, and I just drove to Key west and back, loaded with camping gear and my dog. Went out of the way and stayed in the Outer Banks for a few days too. Awesome trip. Second time I've taken this truck from VA to FL and back. No hiccups.

[newnissanfanatic]

I have a 84 z24 that is carbed and was wondering if anyone has done a reverse conversion and turned a carb into an EFI. I assume some of it is the same change, but I was looking for any problems other people may have had before I dive into the swap.

[seang]

I have a 84 z24 that is carbed and was wondering if anyone has done a reverse conversion and turned a carb into an EFI. I assume some of it is the same change, but I was looking for any problems other people may have had before I dive into the swap.

What is a good reason to do that? Not flaming you, just asking.

[newnissanfanatic]

Better gas mileage, I use my truck as a daily driver i plan on droping 3" and custom exhaust with cherry bomb mufflers. Plus my choke on my current carb sticks if it sits for a couple of days.

[newnissanfanatic]

Better gas mileage, I use my truck as a daily driver i plan on droping 3" and custom exhaust with cherry bomb mufflers. Plus my choke on my current carb sticks if it sits for a couple of days.

[Frankie Pintado]

Chokes always find ways to malfunction and will give you issues. And if gas is your main concern, then disable that bad boy and move on with your life. If you clean it out and hit it with some marvel mystery oil it might just start working.

You will actually get better gas mileage with the weber carb, as long as you don't race. The original Throttle Body Injection unit is a pretty solid design, but it's "first generation" fuel injection technology. It was the very first step in the transition from carbs to EFI. The Weber, however, has been around for at least 60 or 70 years, and is still being refined. It is far from "first generation". While generally, fuel injection is a much more precise and efficient way to go, that is not the case here.

It would be much easier and make more sense to upgrade your current carb to something more modern.

Or..
Go all the way and drop a KA24 in there with a real fuel injection system.

[mirageshepard]

I've got a holley 5200 which is about the same as the weber, I am going to try & use it but I'm having an issue finding the right throttle linkage & I've been thinking of ways to fab up a linkage out of sum sort of small pulley, but I'm going to try & see what other idea's were available. It looks like a holley 5200 but numbers are sketchy when I try to find "specifics" on the carb. I've also been looking around for an adapter plate that bolts directly to the intake with out drilling, but I haven't found anything concrete yet. I seen this 1 site that had a list of adapter plates shown & seen 1 that looks like it may fit without drilling but I haven't gotten an e-mail back yet when I sent 1 to ask about it "its been a couple weeks" http://www.carburetion.com/Weber/invtoc ... =99004.336 but any advice would be helpful. Oh yeah 2 more things, would the engine light come on & how hard is it to get to if I had to remove it & when I slap on this carb...what emissions junk can I remove & it still run fine?

[mad-max]

The stock distributor, assuming it was working before, will work just fine with no modification. It will base your timing advance only on engine rpm's, because you are removing all of the sensors for things like: air volume, temperature, throttle position, etc. The computer will do this automatically when you disconnect the sensors. It is already the computer's back up plan, should an important sensor fail. I have mentioned that I run a '72 VW this way (no computer, "but a centrifugal advance distributor", which bases the timing on rpm's). It was originally set up with vacuum/centrifugal but runs cooler now (it's aircooled), and will actually last a little longer between head jobs.

Basically anything that the computer used to do to try to compensate for variables in the running environment, will now be compensated for by your foot.

OH MY GOD!!

ive been seeking this info for quite some time but for a nissan rb25 carby build.... ive currently done a rb30 carb build and used a vacuum advance dizzy that comes stock for rb30's. (works great i might add and runs a nice 40 dfav carby :p)

so im still a bit gob smacked about this but what your saying is you had a efi car with an ecu and cas? and you slapped a carb on it and it still advances the timing??

if so this is great news for me pls confirm wether or not this will work on an rb20de/25de ecu and cas

[rogueroughneck]

Frankie!!!!!! this is it man, what I wanted to do to my pick up... it's an 87, TBI Z24i and just not working for me, half throttle or more kills it, like it isn't getting gas, or is flooding...... tired of the computer and injectors and junk, just want a carb! so, to clarify, here is my confusion...

1. can I use the stock dist, (CPS)? or will a regular dizzy work?
2. did the throttle bracket take much? I can fab most anything.... stock cable right?
3. can't I just swap a carbed intake onto the head, and toss the TBI intake unit as a whole? or do the ports not match up?
4. what is the better carb to go with from weber? I can get my hands on a 44mm SE CV carb from a harley big dog, and had one on my 87 Samurai DD/RocKrawler, it was sick, great gas mileage, and was turning 33's @ 75mph.... should be the same right? gas, plus spark, plus air and we have ignition!

any ways, thanks for your posts, I think you hit the nail on the head on this one... I was wondering how to go about it and here it is! computer don't know the difference, everything is just the same, other than the crappy TBI stuff! same comp, same dist. (CPS) haha... nice..

[Frankie Pintado]

I've put over 20k (rather abusive) miles on this truck now, no problems whatsoever. I just put some 16" wheels on it with some bigger tires.

OH MY GOD!!

ive been seeking this info for quite some time but for a nissan rb25 carby build.... ive currently done a rb30 carb build and used a vacuum advance dizzy that comes stock for rb30's. (works great i might add and runs a nice 40 dfav carby :p)

so im still a bit gob smacked about this but what your saying is you had a efi car with an ecu and cas? and you slapped a carb on it and it still advances the timing??

if so this is great news for me pls confirm wether or not this will work on an rb20de/25de ecu and cas

Well I don't know, but I know how you can check. See post below.

Frankie!!!!!! this is it man, what I wanted to do to my pick up... it's an 87, TBI Z24i and just not working for me, half throttle or more kills it, like it isn't getting gas, or is flooding...... tired of the computer and injectors and junk, just want a carb! so, to clarify, here is my confusion...

1. can I use the stock dist, (CPS)? or will a regular dizzy work?
2. did the throttle bracket take much? I can fab most anything.... stock cable right?
3. can't I just swap a carbed intake onto the head, and toss the TBI intake unit as a whole? or do the ports not match up?
4. what is the better carb to go with from weber? I can get my hands on a 44mm SE CV carb from a harley big dog, and had one on my 87 Samurai DD/RocKrawler, it was sick, great gas mileage, and was turning 33's @ 75mph.... should be the same right? gas, plus spark, plus air and we have ignition!

any ways, thanks for your posts, I think you hit the nail on the head on this one... I was wondering how to go about it and here it is! computer don't know the difference, everything is just the same, other than the crappy TBI stuff! same comp, same dist. (CPS) haha... nice..

1. yes, and also yes
2. The stock throttle cable bracket required 5 minutes worth of grinding with a handheld "dremel". I marked it with a sharpee and ground off a corner. Easy Easy Easy.
3.Yes. Yes they do match up. However if you own a drill, that's the only expensive tool required to Adapt your current intake. You will also need a hammer, a punch, a block of wood, and a set of tap and dies (10$-$20).
4.I'm not really sure, but I would advise getting one that would be recommended for the carbureted z24. There are several to choose from, and depending on the source may need to jetting adjustment. The Redline ones are all setup for this engine, and they have 3. There are two basic types of webers (they both have 2 barrells): 2-barrells, and progressives. "2-Barrells" open both barrells at once and transition between 2 sets of jets, the "idle jets" and the "main jets". The progressives operate on one of the two barrells up to about half throttle, then they open the other (usually larger barrell) for power.
The one I have is a "2-Barrell". It makes great power, but In my experience the progressives are smoother and give better mileage. I prefer the "2-barrell" because I have had such solid performance out of them, but I can still cruise (up to about 60mph) on the idle circuit if I'm trying to save some gas.

[rogueroughneck]

Awesome Frankie, thanks for posting back! I am actually putting in a new computer into mine as we speak, I don't think that with only firing on the exhaust side and not firing on the intake side, a weber is going to do much right now. so I am working out all of the bugs as we speak. but I have this bookmarked for the future! thanks again!!!

[Frankie Pintado]

OH MY GOD!!

ive been seeking this info for quite some time but for a nissan rb25 carby build.... ive currently done a rb30 carb build and used a vacuum advance dizzy that comes stock for rb30's. (works great i might add and runs a nice 40 dfav carby :p)

so im still a bit gob smacked about this but what your saying is you had a efi car with an ecu and cas? and you slapped a carb on it and it still advances the timing??

if so this is great news for me pls confirm wether or not this will work on an rb20de/25de ecu and cas

I could have explained this better. In fact I don't think I even told you a correct procedure so scratch what I said earlier.

Note: DO NOT SPRAY CARB CLEANER DOWN THE INTAKE OF THE TBI UNIT. I'm not saying I've never done it and gotten away with it, but it's a really bad idea. The sensors in the tbi just don't like it, and as I've mentioned they are quite expensive.

Find a way to disconnect just 1 important sensor, like the air flow. You know the computer is gonna have to use a pre-programmed formula if it lacks incoming air data. If my memory serves me (uh-oh), the harness for the "air flow meter" also runs the TPS, so you will have to identify the wire color for the Air meter and disconnect only that. Note the the throttle position sensor should remain connected. Then it should still run, with the engine light on, and you can check the timing. Keep in mind that during this test the computer is "ballparking" your fuel mixture so it may not run as well as usual.

The other method is to disconnect the TBI completely and use hook up a special little tool (you need proper equipment and to follow a strict safety regimen) to a propane bottle, and run it into a vacuum port so you can run it without the tbi. If you are in a shop this is probably the fastest way.

Or the most primitive...

You can disconnect the harnesses from the TBI. Find a vacuum port on the intake manifold that is before the manifold splits to the individual cylinders. Hook up a piece of rubber hose. Spray bursts of "carb cleaner" into the hose to get it running and work the throttle (from under the hood). Unless you have some help, this is it. If it seems to run and rev well, it's probably doing what it should. If you have help, get someone to check the timing while you do this and you'll know for sure.

Actually that's not the scariest way to check. I have a worse one that for safety reasons I can not recommend, and that's all I'm saying about that.

[greg510]

I found this page after having problems with my throttle body on my 1988 King Cab.

It was going to be to much money to fix the throttle body,plus I could not

Find all the parts

I figured I would go the Weber route since I have had Webers on a few car including my 72 510 that I still have

I pretty much did what Frankie layed out. As far as the fuel line set up I did not touch the ECU,CPS,timing,etc either . Just more or less bolted the Weber 32/36 on !!! The stock linkage works as well.

I did not drill or tap the manifold,I put the carb on a bit different,I even used the stock mixture plate as my adapter plate.

I will post some pics ...(when I can figure out how to...HA:)

This is a link to the truck running.

http://s992.photobucket.com/albums/af42 ... verted.mp4

The truck idles nice and the throttle is responsive.I have not hooked the choke up yet.Will do that soon as it is starting to get colder out now.

I have re routed the fuel lines and the main linkage spring since this video

To tidy things up..Again will post pics when I figure how to!!!!!

Jet settings are

(Primary) 130 main,65 idle,175 air F50 emulation

(secondary) 150 main 50 idle,190 air F50 emulation

[Frankie Pintado]

Awesome Frankie, thanks for posting back! I am actually putting in a new computer into mine as we speak, I don't think that with only firing on the exhaust side and not firing on the intake side, a weber is going to do much right now. so I am working out all of the bugs as we speak. but I have this bookmarked for the future! thanks again!!!

Isn't it remarkable that these engines will run on either set of plugs? It is sort of a redundant system (with limitations). The secondary coils fire 10 degrees later than the primaries, and cut off at about 2500 rpms, so it will run like s***, but it will run.
I actually tried making both coils fire at the same time for awhile. It worked great, until I had to climb a long hill and it would start knocking. I messed with it for awhile but would consider that experiment to be a failure
But the two coils are the same part#, so If you ever lose the primary coil (or just want a simple way to test it), switch the three wires around and you can use your secondary coil as a primary to get you home. I could not tell the difference running with or without the secondary plugs. They're just there to clean up your emissions.

[Frankie Pintado]

I found this page after having problems with my throttle body on my 1988 King Cab.

It was going to be to much money to fix the throttle body,plus I could not

Find all the parts

I figured I would go the Weber route since I have had Webers on a few car including my 72 510 that I still have

I pretty much did what Frankie layed out. As far as the fuel line set up I did not touch the ECU,CPS,timing,etc either . Just more or less bolted the Weber 32/36 on !!! The stock linkage works as well.

I did not drill or tap the manifold,I put the carb on a bit different,I even used the stock mixture plate as my adapter plate.
I will post some pics ...(when I can figure out how to...HA:)

This is a link to the truck running.

http://s992.photobucket.com/albums/af42 ... verted.mp4

The truck idles nice and the throttle is responsive.I have not hooked the choke up yet.Will do that soon as it is starting to get colder out now.

I have re routed the fuel lines and the main linkage spring since this video

To tidy things up..Again will post pics when I figure how to!!!!!

Jet settings are

(Primary) 130 main,65 idle,175 air F50 emulation

(secondary) 150 main 50 idle,190 air F50 emulation

That's awesome. I think I get what you did with the stock "mixture plate". Brilliant.

I donated mine to my school because they didn't have an example this antiquity. Now I feel like I missed the bus on that.
Please share how exactly you did it or I'm gonna have to speculate, 'cause I think it may be a serious refinement to the conversion procedure.

[Frankie Pintado]

I've got a holley 5200 which is about the same as the weber, I am going to try & use it but I'm having an issue finding the right throttle linkage & I've been thinking of ways to fab up a linkage out of sum sort of small pulley, but I'm going to try & see what other idea's were available. It looks like a holley 5200 but numbers are sketchy when I try to find "specifics" on the carb. I've also been looking around for an adapter plate that bolts directly to the intake with out drilling, but I haven't found anything concrete yet. I seen this 1 site that had a list of adapter plates shown & seen 1 that looks like it may fit without drilling but I haven't gotten an e-mail back yet when I sent 1 to ask about it "its been a couple weeks" http://www.carburetion.com/Weber/invtoc ... =99004.336 but any advice would be helpful. Oh yeah 2 more things, would the engine light come on & how hard is it to get to if I had to remove it & when I slap on this carb...what emissions junk can I remove & it still run fine?

I'm sorry I must have missed this one. I try to reply to everyone.

There is no adapter plate at this time for the z24i intake manifold. The ones you are looking at will match the carb, but not the manifold. You will have to fabricate something or have it fabbed. Same with the linkage. I usually don't see pulleys in the linkage because the cable glides so well in its "tube" anyway. You just need to find the right length cable (the stock one worked for me) and have a bracket to hold the end of the "tube" a few inches from the carb.

I have no reason to think that this carb wouldn't work, with proper jetting. You can remove pretty much all of the emissions stuff (not legally) and it will probably run better than ever. None of it is helping your performance. it's just a matter of what you can get away with wherever you live.

[dongatta]

I can't find much info on this easy mod, so I'm posting what I've learned. Feel free to correct me on any details here. I wouldn't try this if I had to pass emissions.

So I bought an 86 d21 with 72,000 miles on it for $250. It did not run, but had perfect compression and a good spark. After lots of time trying to diagnose the fuel injection, I discovered:I had bad injectors - stuck open, very unusualI had burned capacitors in my eccm - the ones that control the injectorsAll these parts, assuming that nothing else was f'ed up, would cost in the ball park of $800 - $1000. Now enter the Redline Weber...

Redline Weber makes several replacement carb kits for the 720 pickup, and the carbureted version of the d21. They do not make a kit for the fuel injected version of the d21. However, all three trucks came with the z24 engine (we're talking about four cylinder here), but the injected z24 is known as the z24i. The differences (that we're concerned with) between the z24 and z24i are: The FI version uses the computer to control the timing on the spark. That thing that looks like a distributor is actually a crank position sensor. On the z24, there is an actual vacuum-advance distributor.The intake manifolds are different.

I've gathered that the easiest way to do this swap on a fuel injected truck is to take the intake manifold and the distributor from a carbureted engine and install them on your FI engine. Then change the fuel pump out for something meant to give the 2-3 psi you will need at the carb. The original fuel pump should be pumping close to 22psi, way too much. It willl just flood the carb till gas comes out of your air filter in about 6 seconds.

OK so sounds great, but there are issues with this plan. Mainly, availability. I had a hell of a time trying to find those parts. I just don't have time to scour junk yards between two jobs and being a full-time student in Automotive Technology. The fuel pump doesn't score high on difficulty, but there is a much easier, better way.

First I took the old TBI unit off, along with the heater (the honey-comb thing) that sits under it. I then test-fitted the new Weber 38 Outlaw that I picked up directly from the company for $338 after shipping. The two studs on the left (left being the drivers side) lined up almost. I widened the the holes in the base of the carb, just a little and it slid down onto the manifold. For some reason, the holes in the adapter plate did not need to be widened.I did end up using the supplied adapter plate because the holes in it line up with some pretty good places to drill and tap some holes.

I stuffed some plastic grocery bags down into the intake to catch any metal shavings. I made a guide for the drill using a block of 2x4 and a square. I made a nice dent with a punch and hammer to start the hole and drilled.

I tapped the holes to match the adapter kit. This is what I ended up with. Looks funny, but I swear it lines up perfectly.

I liberally applied permetex to both sides of the adapter gasket, and used blue threadlock on the bolts. I also ground the top of the bolts a little prior to installation to make sure that they would not stick up. This picture is letting the permetex dry.One of the more difficult parts of this job is tightening the nuts on the carb. Surprising. Btw use some blue threadlock.Throttle cable bracket took a little work with the dremel.

Now the fuel delivery system, here's the good news: you can use the existing pump and the return line. You will need a "T" fitting, made of metal preferably that is 6/16". Now hook up fuel inlet to the "t". You will need some restriction in the return line, so find about 1" of 1/4" fuel hose, lube it up real good with some synthetic oil or something, and shove it into the return line. Now hook up your return line to one of the fittings on the "t". That leaves one fitting to run through a fuel filter, adjustable fuel pressure regulator (available at any major parts store) and then into the carb. I also installed a permanent fuel pressure gauge because I was experimenting and this made things easy. That is of course optional, but for $25 it's pretty handy to know what your fuel pressure is.If you look closely at the return line, you can actually see the bulge where the piece of 1/4" hose is. It's just passed the "T".

Oh and you'll need to filter your PCV air (1/2-3/4" tube coming off the top of the valve cover. Other than that there are many ways to hook up emissions stuff, all detailed in the instructions that come with the carb. I myself plugged all vacuum lines and it runs perfectly. Better than it ever has.
Modified by Frankie Pintado at 12:32 AM 7/5/2009

Hello I am a new member with a z24i thats driving me crazy. Is the intake in your pictures the z24i. Also would you happen to know the measurements of the bolt pattern on that intake. I am working on a adapter plate

[john1983]

What fuel pressure regulator did you use? What was the PSI on it?

[Frankie Pintado]

Hello I am a new member with a z24i thats driving me crazy. Is the intake in your pictures the z24i. Also would you happen to know the measurements of the bolt pattern on that intake. I am working on a adapter plate

I have no idea. I didn't even have to measure it to do what I did.

What fuel pressure regulator did you use? What was the PSI on it?

Adjustable, from autozone or any other harry homeowner parts store. I keep it set at 3psi. Pay close attention to the simple diagram I drew because you can't run the stock fuel pump directly into the fpr or you will break the fpr.


OK Update

Coming up on 30k any day now. I've just had to perform some maintenance. Hey nothing's perfect.

The top gasket in the weber carb failed. You can tell when this happens because you will see some greasy, gassy gunk forming at the gasket on the outside of the carb. The base gasket also failed at about the same time. They were both made of Chinese newspaper, so no wonder. I guess some people would go buy a rebuild kit and a base gasket. But this is a low-buck champion; no need to start spoiling her now. I just cut a gasket with a razor blade out of some high quality rubberized gasket paper (It will probably last 50 years). I used a dremel with a wood carving bit to cut out the small holes. I've cut many a gasket, I cut a whole rebuild kit at a rest stop once for my '72 ghia. Don't buy the kit, just trace and cut the motherf****r.

Also I've gone through some vacuum caps. I keep a couple in the glovebox.
I just replaced both front wheel bearings. That's irrelevant, but at only 100k miles? I just thought I'd mention it.
A couple bucks worth of gasket paper and vacuum caps and back to knocking down miles.

[Frankie Pintado]

Ya know, looking back at the pictures of the "stealth" setup, you can clearly see that the upper gasket on the weber was starting to die. See that gunk? Crappy materials, that's what that was. Weber must love selling those $30 rebuild kits.