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black92si

Black92si's Family Owned 1973 Datsun 240z

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Hello everyone. New to the forums and thought I would begin by sharing my Z. 1972 Datsun 240z was purchased by my uncle from the dealer and then later sold to my father. About a year and a half ago my father passed away and left the Z in my care.

I pulled the Z out of storage last winter and over the spring have begun to work on her and so far she is being very receptive to being woken up. Trying to sort threw a high idle issue that I hope some fellow Z guys can help with. So without further wait here is some pictures I've taken along the way.

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Looks like it's in great shape! BTW, that's a '73 model year judging by the equipment. ;)

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Yes, great looking family heirloom. It has flat topped carburetors from '73 like Leon says above but the ID plate on the driver's door jamb will say for sure. Unscrew the black knobs on top and make sure they have oil in there. I just bought some at Lowes, 3-in-one 20 wt. in a blue and white bottle for $2.99.

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The renowned Mr. Brown likes his twin brother very much. What a beautiful example.

Cheers, Mike

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Thanks guys!

You are correct it is a 73. It was late last night when I made the post.

My door plate says 11/72 and the hood and title say 73. I assume being a late model 72 they threw the 73 stuff in and out the door she went.

I have unscrewed the caps and half pulled them out (scared of the carbs LOL) I felt resistance so I assumed they still have oil. Do you pull them completely out and flash light check?

I'm in the process of sorting a high idle issue. When the motor gets to temp the idle settles in at 2000 rpm. I'm replacing all rubber hoses that ive come across so far but with no luck.

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The 1973 model year actually started with production in August. I'll correct the thread title.

Welcome! It's a great looking car.

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You may have seen on this site, or if not you soon will, that a common swap for '73's is to put '72 or earlier carburetors on in lieu of your existing "flat tops" that the two posts above refer to. These are a bit simpler and more reliable once you get them set up, and they allow you to bypass a bit of the smog equipment. Nevertheless, I think the flat tops have similar idle speed adjustment screws that you could try backing off to see if the idle speed comes down. One of the stickers on your air box may even show their location. Other than that you may have a choke that is sticking and causing the idle speed to be too high.

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Thanks for correcting the header of the post admin.

Tlorber I have read about the 72 swap but i'd like to keep my Z in as original condition as possible.

Honestly I've always been a early 90's Honda guy and have no real experience dealing with carbs. I've been trying everything I can think of doing to avoid touching the idle screws.

If I do decide to do the route do you have to adjust both at the same time?

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I'm with Rob on this one, much as I liked my round-top carbs. We are 40+ years down the road now. There are very few 240Zs left that retain this kind of originality. Like my previous car, I would not do anything to that car that was not 100% reversible, and even then I'd want those reversible mods to be hidden if possible. You can see modified Zs anytime. A stock '73? Not so much. I'd start hunting for a nice set of stock hubcaps if it were mine.

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JD,

I agree with your decision to keep the original carbs since this car already retains most of it's originality. I was also thinking about Arne's comment and would guess a lot of the '73 240Z's no longer have the original carbs. In the past I've seen a few posts (on here) regarding the flat top carbs and getting better performance out of them. As far as original hubcaps, they come up for sale occasionally on Ebay, Craigslist, and Datsun Classified and generally run between $200 to $900 for a pair (depending on the condition).

Robert S.

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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 by Captain Obvious
Forgot some stuff

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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.

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Edited by black92si
cleaned it up from my phone

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20140523_202114.jpg

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

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

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

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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?

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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 by Captain_Zeros

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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.

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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 LOL 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 by black92si

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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?

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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.

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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.

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