I have a 1984 Nissan 720 with Z24 engine.

[xe2dy]

Hello, I just moved from California to Nevada. Since I'm now in an area that does not require smog tests I want to remove the existing emissions system and install a standard two barrel carburetor. I have a 1984 Nissan 720 with Z24 engine. Would greatly appreciate any ideas on how to do that. Thanks in advance!

[datzenmike]

Unplug the old ECC carburetor 6 pin connector. Make sure the replacement Hitachi will fit the bolt pattern... it should if a Z24 carburetor. You can cut the old plug off the carburetor and wire the RED idle cut solenoid and BLUE choke heater wider to the new carburetor. Trim the other not used wires short and just plug it into the engine harness.

 

Here is the wiring for the old ECC California carburetor. All you need do is connect the RED to the RED anti dieseling solenoid and the L (Nissan code for BLUE) to the replacement carburetor's BLUE auto choke heater.

 

 

The box under the seat you can do what ever you like with it. It's no longer connected to the carburetor.

 

The other emissions equipment probably is in good working order and can just be left alone. It has little effect on running and that only at part throttle.

[720_Jeff]

In Nevada, looks like you'd need to register the truck as a 'classic'.  The other part, your only permitted to drive 5,000 miles/yr, but not sure how they'd enforce that, if there is no smog check.

 

[xe2dy]

Thank You datzenmike, You've always been helpful to me and others. 

 

A few more questions please. 

 

A) How much of the existing emission items and vacuum lines can I remove? 

 

B) Can I use the original air cleaner? Do I need to plug up any holes from removed vacuum lines? 

 

C) Do I disconnect the B.P.T valve and only connect the E.G.R valve to the front vacuum hose nipple on the carburetor base?

 

D) Can I remove the vacuum control valve?

 

E) Can I run a vacuum line from the up pointing nipple on the carburetor base directly to the line that leads to the vacuum advance that's next to the distributer? 

 

F) Can I plug all three (3) nipples on the Thermal vacuum valve? (top of intake manifold) 

 

G) Can I remove both vacuum switches and A.B. valve from the fitting on top of intake manifold. Then connect vacuum line to each nipple? (two plcs)

 

H) Can I disconnect the canister? (Driver side of vehicle adjacent to distributer)

 

I) Can I remove the catalytic converter? 

 

My reference is the Nissan Pick Up 1984 1st rev Service Manual EF & EC-9 / SEC269A 

I believe I have the M/T MODEL

 

Thanks in advance for taking time to address the above.

 

Ed Bradshaw

[datzenmike]

4 hours ago, xe2dy said:

A) How much of the existing emission items and vacuum lines can I remove? 

 

Just about everything but the vacuum advance hose to the distributor. Straight to the vacuum advance no other Ts to something else.

 

4 hours ago, xe2dy said:

 

B) Can I use the original air cleaner? Do I need to plug up any holes from removed vacuum lines? 

 

The air filter can be used. There is a 1" metal hose from the exhaust manifold to a one way reed valve on the air filter for drawing in air to add to the exhaust to give the catalytic converter oxygen to burn off impurities. As the converter is going so too can this hose.

 

4 hours ago, xe2dy said:

C) Do I disconnect the B.P.T valve and only connect the E.G.R valve to the front vacuum hose nipple on the carburetor base?

 

Well I assume that you will be removing the EGR and bolting a cover plate over the hole so there will be no need to keep the BPT, vacuum lines to the BPT from the carburetor and between the BPT and the EGR valve. The metal line from the EGR back around the head to the exhaust manifold can also be removed and the hole in the exhaust filled with a pipe plug.

 

 

4 hours ago, xe2dy said:

D) Can I remove the vacuum control valve?

 

As there will only be a hose directly between the carburetor base and the vacuum advance, the vacuum control valve will not be needed and removed.

 

4 hours ago, xe2dy said:

E) Can I run a vacuum line from the up pointing nipple on the carburetor base directly to the line that leads to the vacuum advance that's next to the distributer? 

 

Yes. See A) above

 

4 hours ago, xe2dy said:

F) Can I plug all three (3) nipples on the Thermal vacuum valve? (top of intake manifold) 

 

Nothing worse than something disconnected and just left there. If disconnecting the TVV might as well remove it from the intake like the EGR. Take to a fastener store and get a pipe plug with the same thread. Do this for the exhaust manifold too 

 

4 hours ago, xe2dy said:

G) Can I remove both vacuum switches and A.B. valve from the fitting on top of intake manifold. Then connect vacuum line to each nipple? (two plcs)

 

There are two vacuum switches mounted over on the passenger side fender. They have a common vacuum hose to the intake. They can be removed. For now plug the fitting on the intake*.  See bottom page

 

4 hours ago, xe2dy said:

H) Can I disconnect the canister? (Driver side of vehicle adjacent to distributer)

 

I would advise you not to remove the canister and to keep it operational. It has no effect of running whatever and it's job is to collect gas vapors from the gas tank and the carburetor float bowl. If removed these fumes have to go somewhere and can get into the cab. I don't think you can plug the line to the tank as it's the vent that allows air into the tank as it empties.

 

4 hours ago, xe2dy said:

I) Can I remove the catalytic converter? 

 

If you want. The EGR is gone and the hoses that draw fresh air in. See B) Just use a straight pipe.

 

4 hours ago, xe2dy said:

My reference is the Nissan Pick Up 1984 1st rev Service Manual EF & EC-9 / SEC269A 

I believe I have the M/T MODEL

 

Thanks in advance for taking time to address the above.

 

Ed Bradshaw

 

Not mentioned is the PCV valve. Definitely do not remove this fantastic device that easily extends engine life by twice by removing combustion, gasoline and water vapor from the crankcase that dilutes and dirties the engine oil.

 

Also the AB (anti backfire) valve. It also connects to the intake fitting* See G) above. This system reduces exhaust backfiring on deceleration and it's removal may be annoying and why I have noted it separately. You may want to keep this. It also connects a larger hose to the intake and a smaller one to the air filter. It senses intake vacuum over a set value and bleeds air into the intake to reduce popping. Disconnect the small hose to the intake fitting and see if you can live with the noise. Then remove or not. Plug hole where fitting was for neatness. Affects deceleration, has no effect on running.

 

Here's an example of my (broken) TVV from an L20B that was removed and the hole plugged neatly...

 

 

 

[xe2dy]

A FANTSTIC effort in replying to my questions! Thanks so much for being there for me and others that read this thread! 

[datzenmike]

I was bored and got carried away.

 

[xe2dy]

Follow up question.

 

Regarding the two nipples at the carburetor base. Looking at that area from the passenger side. The nipple on the firewall side pointing up is the one the vacuum line to the vacuum advance connects to. What does the nipple on the radiator side connect to? Does that take a vacuum line to the canister in 'H' mentioned above? 

 

Thanks.  

[datzenmike]

There should be 3 vacuum signal ports.

 

1/ The very rear most port feeds only to the vacuum control valve which adjusts the vacuum advance vacuum to the distributor.This vacuum signal is not available until the throttle opens above idle. Under high vacuum conditions, such as deceleration at high speeds and part throttle, when a pre set limit is met an air leak is introduced to lower the vacuum signal and retard the ignition.

 

 

2/ The middle port is the vacuum signal for the EGR/BPT and also the purge signal for the canister telling it to open and suck the vapors into the intake to be burned. This vacuum signal is not available until the throttle opens above idle. It also has to pass through the TVV which is an air bleed that destroys vacuum till the engine warms up and closes.    

 

3/ The front vacuum port is the vacuum advance. This vacuum signal is not available until the throttle opens above idle. It has to pass through the TVV which is an air bleed that destroys vacuum till the engine warms up and closes. It is also controlled by the vacuum control valve  in 1/ 

[xe2dy]

I'll gather more info tomorrow. However I only have two ports. 

 

Regrading the E.G.R/ B.P.T. valves and the vacuum control valve, I'm under the impression that I won't be using them, correct?  Reference 'C' and 'D' above. 

[xe2dy]

32 minutes ago, xe2dy said:

I'll gather more info tomorrow. However I only have two ports. 

 

Regrading the E.G.R/ B.P.T. valves and the vacuum control valve, I'm under the impression that I won't be using them, correct?  Reference 'C' and 'D' above. 

Also I will be removing the T.V.V. Reference 'F' above. 

 

[datzenmike]

You won't be using them.

 

The EGR valve is usually removed and flat piece of metal is bolted over the opening using the two bolts that held the EGR.

 

Definitely remove the TVV for a cleaner look. It screws into the water jacket so will need a solid plug to seal it.

 

This is a lot of bother for no gain at all other than 3 pounds removed. No one will see this and other than another 720 owner no one will know if something was there or not. 

 

There is a small vacuum line to the air filter snorkel. Keep this so your ATC (air temp control) remains functional.

[xe2dy]

Thank you for responding. 

 

OK, on the Hitachi 2 barrel carb I will use the back port for the straight vacuum line to the vacuum advance. I will use the front port for the straight vacuum line to the canister.  

 

This is the carb I have. https://www.ebay.com/itm/264687333926?hash=item3da0983226:g:bD0AAOSwQXZePleo 

[xe2dy]

2 minutes ago, xe2dy said:

Thank you for responding. 

 

OK, on the Hitachi 2 barrel carb I will use the back port for the straight vacuum line to the vacuum advance. I will use the front port for the straight vacuum line to the canister.  

 

This is the carb I have. https://www.ebay.com/itm/264687333926?hash=item3da0983226:g:bD0AAOSwQXZePleo 

Does the above read correct to you? Thanks in advance. 

[datzenmike]

Looks sort of right. Good enough for Chinese knock off. It's should last a few years.

 

That '84 carburetor at the dealer is $870.00

[xe2dy]

OK. GREAT! Thanks for working with me tonight! I'm 100% confident that I can get Bessie running soon! 🙂 

[Thomas Perkins]

Here is mine...I live in Georgia.Also get rid of the cat and tell Biden his shit stinks...

 

[xe2dy]

Thanks Thomas! Have a GREAT week end! 🙂 

 

[datzenmike]

23 hours ago, Thomas Perkins said:

Here is mine...I live in Georgia.Also get rid of the cat and tell Biden his shit stinks...

 

 

Keep the stinky cat and get rid of biden