Carbs on, next step vacuum hoses

[MariaAZ]

I've got the SUs on the 260Z, and would like to know if I'm doing everything right so far. I'm debating using a different air breather than the stock one.

So far, I've:

Connected a water hose from the outlet near the firewall to the outlet on the thermostat housing (used to go through the flat top carbs) Would it be better just to plug these outlets?

connected the hose that comes from the vacuum advance on the dist. to the front carb. This also seems to go to the throttle opener valve

There were a few broken hoses when I pulled off the air breather, and I'm not exactly sure where they all go. The hose with the PCV valve looks to go to the air cleaner. There's another broken hose at the cranckase. I'm suspecting that perhaps these two should be connected with a hose?

I still have the air pump, and don't know what to do with the hoses for it, either. I don't mind keeping it, if it can be made to work with the earlier air breather.

[Zedrally]

I'm a little confused here?

Have you changed the SU's from Flat Top to Round?

If you have then the air filters are different.

If this is the case consider de-smogging the engine [if you are allowed to] & use either a 240 air box or socks for filters.

Perhaps a search under de-smogging will answer your questions.

HIH

[MariaAZ]

I've installed '72 round tops & air box on the 260Z. Arizona requires all cars built after 1966 to be emission-tested. I've removed several components of the smog equipment, trying to keep as much on as possible (which isn't much with the '72 air box.)

My biggest concern is getting the numbers low enough to pass emissions. I checked past posts & have found reference to lower CO & HC numbers after the carb conversion. Are there any AZ 260Z owners here who have stripped off the emissions stuff & still passed the smog test?

[beandip]

you may have a problem passing emissions with the round tops. For your information the dealers installed roundtops on cars when the new owners complained loud and hard about the poor prerformance of the new '73 and '74s I dont know if this helps , but this is the trooth. You might need to use the flat tops to pass the test and then change after that. I had to do this with my GTO when I lived in calif.

[Masashi]

Hi mariaAZ,

Finally you got 240z round carb? So you should check other's engine photo at gallery first. I also put photo but mine is not so good modification.(Last time I recomend good modification 260Z to 240z carb right?)

Basically all polution system and water line to carb are no need in my opinion. Arizona and Nevada is almost same law regarding smog test.

My ex boss in Canada was work for Nissan and this is his advice.

I also had 260z in Canada.

In my case just take every thing (valve, EGR) then put plug on .

and overhall carb especially air line and change oil (ATF) *this must correct level.

Then adjust mix with bottom screw and top screw (this is for idle only)

Water line is still no problem in winter but summer time this hot water coming to carb cause parcoration (become too rich)

If it's round carb, you can reduce smog I believe.

Take it easy !

[beandip]

were you able to obtain the thicker spacer that installs between the intake and the carb ? Connecting the vacum line to the port at the base of the front carb is correct . Connecting the water line up that goes thorugh the intake manifold is wise if you live any where it is cold in the winter and 90+ in the summer. It evens out the temp and aids in warm up in winter and helps to cool the carbs in summer from conducted and raidiated heat from the intake and exhaust manifolds. The hose form the block to the air cleaner is supposed to have a PCV installed in it to aid in keeping the engine clean. The air pump is ok to keep if it is still working and not frozen . The air pump will not effect performance either way but will most likely be needed to pass emissions. When tuning the engine for emissions testing , set the mixture lean for the test and readjust to correct after you are done. the '73 Zs had trouble with vapor locking and with the flat top carbs , so Datsun installed electric fuel pumps and wrapped the fuel rail with insulation to help solve the problem. With the round tops you should not have any trouble if you are using the thicker bakeolite spacer and water going thorugh the intake. :classic:

[MariaAZ]

I was not able to find the thicker spacers yet, but i DID replace the studs so I could get the carbs on.

After getting everything plugged or disconnected, I fired up the ol' Z and she runs like crap. The engine surges on its own, like someone is rhythmically stepping on & releasing the gas pedal, so it's virtually impossible to get the carbs balanced.

I was told by a mechanic who works a lot on Zs that the carbs probably need to be rebuilt, as the backfiring (which I can get rid of by richening the fuel mix) and surging sound like worn internals. I've located a pair of rebuilt 4 screw carbs that will be mine when they are completed in February, so I guess I'll just have to wait.

In the meantime, I still haven't figured out how to completely remove the EGR valve from the manifold. It doesn't look like it can be completely unbolted unless I have something fabricated to cover the inlets & with a mounting bracket for the accellerator.

Also, is there any benefit to leaving the anti-backfire valve? If I remove it, do I just let the connector for it on the throttle linkage flop around freely?

[beandip]

on the adjustment of the round tops . When you reach under th e carb where the small fuel hose connects to the bottom of the carb there is an mixtrue adjustment. Turn this counter clock wise unitill it stops , then back it off clock wise 21/4 turns and start the engine and see how she runs . The back fire could be a lean pop and in this case just rurn the adjustment clockwise 1/4 turn. there is a section in the tec area on this . Gary

[Go240Zags]

Here's a place to find the thicker spacer, from a post I did under parts swapping.

The thicker spacer/insulator/gasket number number from NAPA is NGAG30694. You can find at:

http://www.napaonline.com/cgi-bin/ncommerce3/ExecMacro/NAPAonline/search_results_product_detail.d2w/report?prrfnbr=23486580&prmenbr=5806

So to review:

240Z (E88) manifold used with early SU carbs: Part # NGAG30694

I'd like to see a good diagram or photo of the 240Z early SUs, balance tube and linkage, as well as where all the hoses, throttle control, etc. link up. I've gone to that microfisch site and the diagrams are kind of hard to read.

I have my own Microfiche CD I need to check and see if the diagrams are better. Once they get past the carburetor removal, re-build and re-install most of the aftermarket manuels just don't go into detail about the balance tube and connections, especially if the book is trying to cover 240Z, 260Z and 280Z IMHO.

I've attached a picture of my 70-71 SUs with the N36 intake from a 260Z. I need to go to the narrower spacer to get the washers, lock washers and nuts to fit properly for the carb attachment. Where can you find the thing on the balance tube that I believe controls the rate of throttle return or deceleration and what's it called.

Thanks for any help you can give.

Gary

[dogma420]

Something to think about....

If at all possible, make the early Zs air filter box work with your emissions, as the air horns built into it are optimized for the round tops.

The square air horns on the 74 air filter box hurt the early su's.

Just 2 centz...good luck.

[MariaAZ]

I KNEW there had to be a reason I just couldn't get the 260 airbox to work on the SUs! A couple of pieces were missing from the mounting plates, so I just removed them and popped on an early airbox that I happened to have lying around

[dogma420]

for passing emissions, you can get an adapter so the 74 flat top air filter housing fits, i know ztherapy.com carries them.

other than for emissions, i wouldn't use the 74 air filter box, it sux just like the flat tops.

Good luck!