I need help changing to Carburetor - 78 280z

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Jan 3, 2004 | 04:35 PM

Zach280z78

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I need help changing to Carburetor - 78 280z

I have a 1978 280z coupe non-California model. I just got it repainted 2003 Viper Red 1 Stage Coat. My fuel injectors have gone to **** and I really don't like regulators. I guess it is just the rebel in me. So I went out and got the 4-barrel Intake Manifold from CarTech, but I'm not 100% positive about the other parts I need to modify to go along with the Fuel-Injection to Carburetor Conversion. Do I need to change the Fuel Pressure Regulator, Fuel Damper, Fuel Pump, etc? Do I just rip out the whole ECU system and all the Fuel-Injection Intake? What sensors do I leave alone? I'd like to think I know what I'm doing out there, but I would rather not take the chance of doing anything wrong.

So PLZ if anyone has done this before or knows what I should do PLZ give me as much information as possible and in detail and if there are any websites you could give me it would be very appreciated THANKS.

Jan 10, 2004 | 08:37 PM

240zprace

Registered User

Joined: Jan 2004

Posts: 27

From: central cali, fresno

dude, stay with efi......

Jan 11, 2004 | 08:54 AM

preith

Registered User

Joined: Apr 2002

Posts: 236

From: Waukesha, WI

You might want to do a search, I seem to remember a discussion on this. Everyone I've come in contact with have not had good experiences with the 4-barrel setup. Most end up going with the SU's and have better luck.

Phil

Last edited by preith; Jan 11, 2004 at 08:58 AM.

Jan 12, 2004 | 10:29 AM

ZChief

Registered User

Joined: Jan 2004

Posts: 125

From: Texas

4bbl conversion

I'm not sure if you are tring to keep it emission legal or not, but you will need to change out your fuel pump and probably your fuel line. You're going to want about 4 psi worth of fuel pressure at the carb, so depending on the fuel pump you use, you may or may not need the regulator. Did the kit come with linkage? If not, you'll need to rig something up for that also.

I had the 4bbl set up on two prior Zs and never did get the performance I was hoping for, however, I have heard of people that have tweaked them out and had good luck. I'm going with the SUs on my 70 model that I'm rebuilding now.

Good luck

Jan 27, 2004 | 11:56 AM

jevil

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Yeah, the 4 barrrel setup is plauged with fuel distribution problems, cylinders 2 and 5 run rich, all the others run lean.

The SU's are good carbs, but if I had a FI setup, I'd fix that before I'd ever go to carbs. They aren't that hard to work on if you get a book and troubleshoot correctly.

Mar 21, 2004 | 07:21 PM

Biggs

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FI for new - Carb for old

I'd stick with FI, as well, unless you have an old Z and desire to keep the original means of induction. In addition, running a downdraft carb on an engine desinged for sidedrafts/FI while relying on a sharp 90 in the intake to handle the flow direction change is asking for trouble. In my opinion, it's an illogical set up.

If you decide to proceed, you will definitley need to install a regulator to choke down the supply pressure to 3 (SU) to 4 (Holley) psi or go to a low pressure fuel pump.

Biggs,

72 240Z
73 240Z
83 280ZX

Mar 22, 2004 | 01:33 PM

Bleach

The Evil Twin

Joined: Mar 2001

Posts: 9,296

From: Seattle, WA

Remove the electric fuel pump from the fuel tank and run the pickup line straight into the tank with no pump or filter.
use the existing fuel line up to the engine compartment.
Remove the FI type fuel filter and use a little Fram filter element for carbs. (mine looks like a little K&N filter inside a clear plastic can)

Get a manual fuel pump from a 240Z and slap that on the front right side of the head. Also, obtain the assiciated front cam bolt and extra lobe from the 240Z. The lobe opperates the manual fuel pump.
Run the hose up to the 4-barrel. (the FI pressure regulator was on the intake manifold. Leave it there, you don't need it anymore) The Holly has its own built in valve or pressure regulator. In reality, there is no regulator. When the fuel bowl is full, the valve comes closed and the fuel is pushed back. You can run with or without a fuel return line. Those manual fuel pumps can take it. They only run 3-4 psi.
Keep your electronic ignition distributor!

Jet that 4-barrel way down. Don't run it till you can smell the fuel coming out the exhaust. Run it to what seems like a little lean at idle. It'll probably still be too rich at full throttle.

I would of said that some stock dual SU's from a 240Z were the best idea, but if you already spent $250 on an intake manifold I guess you really want to use it. The only good thing is you can buy NOS kits for that bad boy!

Mar 28, 2004 | 06:36 AM

AllmyZs

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I agree with the keep it FI, but if you want to carb go SU they are a easier change over and a less headache. You will get better performance and less issues. I would sell you 4bbl on E-bay to get the cash for new injectors or an SU setup. If you think logically you only have 4 bbl carb and 6 cylinders wanting fuel. Some one is gonna get to much and some not enough. I just think you are in way to much in trying this conversion. but if you do it please post pics and updates, we all would like to know how it went.