Carb options for the Z-series?

[Justin]

Hey!

   So I'm curious if there were any "trick" carb set-ups for the 720 z-series engines?

I know they had fuel-injection,and that's the "best" set-up you can get, but I'm way more interested in the "cool" factor carburetors provide.

The L series (510's?) had those trick dual carb set-ups, and a whole lot of aftermarket intakes too I feel like (single side-draft intake, 4-bbl intake, I'm sure there's others,).

I guess I could swap the head for an L-series, but if I don't have to that'd be preferred.

So any cool intakes for these? Or were all the cool intakes for cars?

Thanks guys,

 

Edited February 14, 2021 by Justin

[datzenmike]

I've seen side draft intakes but that won't be cheap. Then there's buying the carburetors for it. The breathing of the Z series head is poor for high performance and I think that side drafts would not reach their potential. The stock carburetor bores are 34/38mm, although this is not a perfect way for estimating the air flow through it. I think the 32/36 Weber might flow better certainly a 38/38 'Outlaw' carburetor will. Perhaps too much and is not as derivable.

[Charlie69]

I have a Weber DGEV 32/36 on my 86 720 and I purchased it right after buying the truck in 2011.  Still runs good and passes AZ emissions every 2 years.

[datzenmike]

Though a 'smaller' carburetor to the 34/36 Z24 carburetor how does it perform?

 

I have a Z24 carburetor and the bores are almost plugged with venturies and what not in the way of flow.

[Charlie69]

Better than the stock carb.  the Weber 32/36 DGEV carb wakes up the Z24 to the point it makes it enjoyable to drive.  I know Mike you are dead fast Nikki, but I have been running Webers on all my Datsun Nissan's since the 70's and also on many of my Harleys through the years. Weber are simple carbs and you do not need an engineering degree to understand them.  KISS applies when it comes to carbs. The more complicated the more parts to fail and the more parts to have to understand what the part does and how it affects the running of the engine when said part fails.

Edited February 17, 2021 by Charlie69

[datzenmike]

Oh I agree on how complicated the Hitachi are.

[Justin]

This fits though, right?

aussiespeedshop.com/product/datsun-nissan-fj20-engine-2-4rs-side-draft-weber-twin-dcoe-manifold-as0750/

[Charlie69]

This is the correct NAPSZ 20/22/24 Manifold.

 

https://www.piercemanifolds.com/NISSAN_NAP_Z_MANIFOLD_LINKAGE_99003_831_p/99003.831.htm

[datzenmike]

14 hours ago, Justin said:

This fits though, right?

aussiespeedshop.com/product/datsun-nissan-fj20-engine-2-4rs-side-draft-weber-twin-dcoe-manifold-as0750/

 

This is for the FJ engine. As you can see the bolt pattern is totally wrong and there is no water outlet on this intake.

 

 

 

 

This one (Pierce Manifolds) will work. It shown upside down but you can see the water outlet on the left. Te thermostat will need to be in line. Maybe that's what that round casting below it is for.

 

 

[A guy named Rick]

How would this work on the hitachi? Just curious.

 

 

[datzenmike]

No advantage really. The second barrel is pulled open by vacuum only when the one barrel is open and the engine revved high enough to actually need it. Like passing or hill climbing. This will work but you would have to drive it knowing that opening too soon can cause the engine to stumble because there isn't enough air being pulled through the carburetor at low speeds. Vacuum secondary saves gas.

 

I guess you could experiment with a lighter spring in the diaphragm to get the secondary to open sooner. It might give a slight increase in mid range power but once revved up it will be the same as a vacuum secondary that is open.

 

The Weber 32/36 is this way. It opens the secondary on demand and kind of bogs if opened too soon.

[A guy named Rick]

Yup I have a weber too, just waiting until I get everything in order and get the truck smogged, then going to cap off the vac lines, egr, and put it on. 

 

I want to go with a header and run catless too. Thinking of just building a whole exhaust to just pop on and then take off every 2 years to get it slogged lol 😆 

[A guy named Rick]

Hell, I wouldn't need an O2 sensor while running a weber.

 

The ECM doesn't control the distributor or timing at all, right?

[datzenmike]

The stock exhaust manifold is not restrictive the head is. I wouldn't waste money on a header but a really nice mandrel bent 2" but no more than 2 1/4" exhaust system and a large muffler would be more than sufficient for the exhaust. This way you don't have to mess with the EGR pipe on the exhaust, it will just be there waiting for you to connect the vacuum line to the EGR valve. Also the exhaust down pipe doesn't have to be butchered to fit a header collector then somehow changed back.

 

The O₂  is only critical to the ignition on the later April '85 and on Z24i engine.

 

[Charlie69]

I run the O2 sensor and the EGR with my Weber.

[datzenmike]

The O₂ is used by the box under the front seat for the ECC carburetor but because the Weber isn't electrically connected it has no effect.

 

You can keep running EGR by using the vacuum advance signal. EGR is not on under full throttle conditions so it really doesn't hamper performance anyway.

[A guy named Rick]

Wait, so you're saying the o2 is critical to the ignition on the later 720's, in what way besides controlling the mixture solenoid? I'm wondering if it messes with the timing at all.

[Charlie69]

To pass AZ emissions every 2 years I have to have vacuum to the EGR and have the O2 sensor in place and wired.

Edited March 8, 2021 by Charlie69

[datzenmike]

6 hours ago, A guy named Rick said:

Wait, so you're saying the o2 is critical to the ignition on the later 720's, in what way besides controlling the mixture solenoid? I'm wondering if it messes with the timing at all.

 

Z24 ECC carburetor.... The O₂ sensor provides feedback to the ECU under the seat so it can tailor the mixture the carb produces. Has no effect on the EI ignition.

 

 

If you are putting a Weber or Webers on it doesn't matter what the box under the seat is doing, it's not connected to this carburetor.

 

 

 

[Stinky]

What part of CA are you in?  You in the part w/a a smog check every 2 years, or the part where you only have to do the check when you sell a car?

 

If you are in the 1st one...it limits your choices.

 

A Holley Weber used to be a cheap alternative.

 

A Holley 2300, or the Autolite coefficient would make it run like a "Striped-Ass Ape."  (Never seen one? See how fast they run).  They also have the possibility of mounting a real air-filter housing on it.  The choices of air filters on a Weber is lacking.  You'll have to fabricate a housing, or run that 2nd rate K&N filter & housing.

 

Webers are prone to having the secondary's stick, partially open if driving in a sandy environment.  That can be good for a thrill.   They are the reason that I put the Autolite on my Pinto powered buggy.   My mech put a motorcycle carb on his rail w/a turboed Rabbit engine because he didn't like the thrill.

[Charlie69]

I have driven many miles of dirt roads in and around Arizona over the 40 plus years I have been running Webers on my trucks and I do regular mantenance on my trucks so I do not experience the "secondary's stick, partially open if driving in a sandy environment.  A blast of carb cleaner inside and outside and then some dry silicone spray lube on linkages and it is good.