Black92si's Family Owned 1973 Datsun 240z

[Captain Obvious]

Beautiful car, and mostly original. Do not fear the flat tops. Keep it original. There are those on the forum who can help if needed.

On a related note... With the flat tops, there is just one idle speed control screw, not two. So if you're looking at two similar looking screws thinking they're the idle speed control, then you're looking at the wrong thing. I suspect you're looking at the synchronization screws, not idle speed.

The idle speed control is on the balance tube between the big arse bolt you're using to plug where the anti-backfire system is supposed to connect and the EGR control diaphragm. Hidden below the black hose that connects your valve cover to the air cleaner backing plate.

Do not fear the idle control screw either. It's predicable and is reversible. Same cannot be said, however, if you start screwing with the sync screws.

However, I doubt the cause of your idle issues is simply that the idle speed control screw is out too far. I bet you've got rotten air tubes, leaky gaskets, vacuum leaks, etc. You know... 40 years of being a Z.

Edited May 24, 2014 by Captain Obvious
Forgot some stuff

[black92si]

Thanks for everyone's kind words and imput. I'm also a huge fan of the butterscotch color.

I've replaced about 85% of the vac hoses so far. I'm about all the way threw them actually and still experiencing the idle issue.

So from what i can tell I'm missing numbers 1,3,9,11,14 also have a small hole in 6.

I snapped some more pictures that i'll add in another post.

Edited May 24, 2014 by black92si
cleaned it up from my phone

[black92si]

Here's a over view of how the bay sits today.

I'm also in the process of getting the correct 73 fuel rail.

I believe the top one is the Anti back fire valve? What do the other 2 go to?

The hose that goes off camera have a screw in it capping it off. I replaced that with a actual vacuum cap but where is it supposed to go?

[Captain_Zeros]

Awesome Z!

260Z Carb Adjustment Manual.PDF

1973 240z 1974 260z fuel system modifications.pdf

As a fellow '73 240Z owner, have a book on flattop carbs and a book on common dealer '73 fuel system changes that aren't well documented in the service manual!

Sadly I can't help your originality, I pulled my flattop carbs because they sat for a decade and gummed up with fuel and swapped them for a set of early carbs that came in the trunk when I bought it.

Edited May 24, 2014 by Captain_Zeros

[Captain Obvious]

It's clear with the earlier fuel rail and the other changes that someone has been messing around in there. Makes me wonder if someone had swapped round tops into there at some time in the past and then went back to the flat tops?

"I believe the top one is the Anti back fire valve? What do the other 2 go to?"

The large top nipple is supposed to go to the anti-backfire valve. The lower large one went to the air pump. On 74, the smaller one I think went to the thermostatic control on the air cleaner. I believe they moved that control valve around a little depending on year, so I'm wondering... Are you sure you've got the original air cleaner for your year, or maybe someone swapped a 74 air cleaner onto your car?

"The hose that goes off camera have a screw in it capping it off. where is it supposed to go?"

That small hose also went to the anti-backfire valve. It was the control signal that told the anti-backfire valve to open when the vacuum got very high.

[black92si]

I sorted out my idle issue today! I barely turned the idle screw down and it responded well. So I adjusted it down to just about 1100 rpm. Much better idle now it was about 2-2200rpm.

Captain As far as I know no one has replaced the air cleaner.

So now I want to check/fill the trans and rear dif. Do you guys have any issues doing this in the drive way? Any tips or tricks?

Edited May 25, 2014 by black92si

[Captain Obvious]

Excellent. Glad to hear that it was that simple. Surprised, but glad!!

I've got an air cleaner housing laying around here somewhere... Next time it turns up, I'll snap a pic of the rear and label all the tubes and connections. Something I've been meaning to do for a while now. This isn't the first time something like this has come up.

Now you need to cap all those unused fittings on the rear or the air cleaner or you need to reinstall the equipment that's supposed to connect to them. With them hanging open, you're sucking unfiltered air right into your carbs.

You download the service manual yet?

[Darrel]

Don't drain the trans fluid until you get the fill plug out first.

[siteunseen]

Any tips or tricks?

http://atlanticz.ca/zclub/techtips/mtl/index.html

I bought my Red Line from amazon.com

Save this link, Tech Tips, you'll use it. Thanks again Blue!

[siteunseen]

I meant to say that I'm not suggesting that you change your fluids to Red Line but you'll get a lot of information from that link on what you're asking. And the pictures are nice too, kind of gets you prepared for what you're about to do.

Have fun.

[black92si]

I will open the fill before the drain. Thanks for the tip.

I appreciate everyone's advice and I hope you guys have a happy and safe memorial day.

I have a busy week ahead of me with the holiday and summer college starting up.