z24i EFI, TBI, to weber carburetor conversion

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dimedriver
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Hey, Do any of you guys who have "upgraded" to normal old distributors and carbs want to sell your old cas computer controlled distributors? I need two of them for some upcoming projects of mine.

I only need the distributors not the computers thanks.

-Dime


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Rev_D21
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Dime, I got my eyes peeled for you. I know of a place that might have one just their yard totally sucks this time of the year. I'll do my best though.

dimedriver
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Thanks,

How is your EFI project going?

-Dime

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Rev_D21
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Snails pace. I had the father-in-law solder up the ecm. I should have that in back in my hands later this week. Other than that it's a little cold to work outside right now so I am taking a short break.

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Frankie Pintado
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Like I said, you relieve most of the pressure by routing the fuel back to the tank via the stock return line. In fact, without the little piece of hose inserted into the return line (to cause some pressure to back up), there is not even 1 psi at the carb and it will idle, but will sputter when you are driving. It needs a little resistance to give low, steady pressure to the regulator and then the carb.

There is no pressure regulator that I am familiar with that drops pressure from 22psi to 2 psi. You will probably break the Mr. Gasket one if you try to make it do that.

This set up is working perfectly for me for over 10k miles. The only thing that I changed was the removal of that plastic fuel filter, which was looking like it may fail. I am getting over 25 mpg (conservative estimate) driving about 75% on the highway, and 25% on short, cold, 10 minute journeys down country roads. I've tested this method pretty thoroughly, it seems pretty solid, and it definitely costs like, five bucks, max. I'd dare say it is probably better than an aftermarket pump because it keeps the fuel very cool, and under pressure, up to the "T"...no chance for vapor-lock.
Modified by Frankie Pintado at 7:07 PM 1/20/2010

rico808
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so frank r u using the original fuel pump or did u change to an electric fuel pump with regulator
Modified by rico808 at 11:42 PM 1/22/2010

t_mertz
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Also to all ive found that 3 port fuel pressure regulators work the best and cleanest look for converting from an efi system to carb. Hooks up feed line, return, and carb fuel line. Supposed to prolong fuel pumps also by releaving pressure so only say 3-4 psi with out holding back some. Look into it the small mr gasket ones seem to be bad from what ive gathered.

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Frankie Pintado
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Stock fuel pump. Stock fuel pump. Stock fuel pump. Stock fuel pump. Stock fuel pump. Stock fuel pump. Stock fuel pump. Stock fuel pump. Stock fuel pump. I never had to drop the tank. Everything was accomplished under the hood. Ya'll are making this more complicated and it's not working any better.

I like the sound of the 3-port fpr, but again, I don't know of any that are designed to work with this FI fuel pump that will give 3-4 psi. A part number?

Also, even with the right 3-port fpr, the pressure in the system would be exactly the same as it would with my design. In other words, it wouldn't be any better for the fuel pump. I know because I tested pressure at every point in my design. If you hook it up the way I've shown, the Mr. Gasket FPR is perfect. It is operating within its specifications, and the stock pump is actually working at a good deal less than its original specifications. I do see slight advantages to the 3-port fpr as far as safety goes. There would be fewer connections, so less potential points of failure.

Now regarding aftermarket fuel pumps:If you choose to go this route you should not need a fuel pressure regulator. Just purchase a pump that delivers 2-4 psi and be done with it. Please note that you will have to remove the fuel tank to do this properly.

Important: The stock pump goes through a safety relay, ever wonder why? Picture this:You have a crash, let's just say some dumbass crossed over the center line and creamed you. You're stuck in the car. Your ignition is on, but that doesn't matter because there are several electrical shorts causing sparks in your crumpled engine compartment. You're fuel line is in pieces, and your electric fuel pump is still going... emptying your tank out under the car... not good.

SO, either run your power from the original power wire (from the stock pump), or add a safety cut off from any FORD vehicle. I really like the ford ones. They sense any impact and shut off. You have to reset them with a button. They always work, and you'll know if someone bumped your car in a parking lot.


Modified by Frankie Pintado at 10:07 AM 2/5/2010

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Frankie Pintado
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rico808 wrote:hey redline said i have to change my stock fuel pump because too much pressure even with a fp regulator it would run for a little while with the stock ones but would only cause to damage the fuel pump is there a carbureted fuel pump that i would be able to switch out with the stock one and how would i hook it up.let me know. Thanks ALOHA
While redline does know their product, they did not even know that this setup was possible when I talked to them. In fact, they told me it could not be done on a z24i because "it has multi-port injection". So at that point I limited my questions to those pertaining to weber products. Please ignore their advice if you want this to work. But if you want to know what you should be concerned about breaking, I can't blame you for that.

So here's what matters if you don't want to break s***. 1. Don't pump 22 psi into your brand new weber.2. Don't pump 22 psi into an adjustable Fuel pressure regulator.3. Don't restrict your stock/aftermarket fuel pump more than necessary, and never more than it was originally. Fluids do not compress, you will break it.

If you do not have any clue as to what I'm talking about at this point, then you should not really be attempting this. You need to understand some basics here. I've literally explained it three times and drawn a diagram. I'll not explain it again. It all works, and will continue to work for a very long time. Take some time and re-read it and think about it.



But this is different, and will work with the stock pump. Now go find someone with some years who knows what they're doing to help you.


Modified by Frankie Pintado at 11:27 AM 2/5/2010

mobius
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Hello, I read your thread and I was wondering if there would be any interest in a mounting flange that would bolt directly onto a z24i intake and accept a weber carb. i have made several mounting flanges for my nissans over the years and was wondering if there would be enough people that want one to justify making a pattern. I have been told that redline makes them, I can find the z24 carb intake flange, but not one for a z24i. This would be one that would bolt on with no machining or drilling.

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Frankie Pintado
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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
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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

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

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Frankie Pintado
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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.

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Frankie Pintado
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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.

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Frankie Pintado
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seang wrote: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
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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
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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.

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Frankie Pintado
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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.
Last edited by Frankie Pintado on Tue Jun 29, 2010 11:36 pm, edited 1 time in total.

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Frankie Pintado
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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
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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
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newnissanfanatic wrote: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
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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
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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.
Last edited by newnissanfanatic on Sun Aug 15, 2010 9:10 pm, edited 1 time in total.

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Frankie Pintado
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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
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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
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Frankie Pintado wrote: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
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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..

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Frankie Pintado
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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.
Last edited by Frankie Pintado on Sun Oct 24, 2010 7:40 am, edited 1 time in total.


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