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DannDZ

Is Walker 15566 the correct carb rebuild kit?

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I have an early 1971 Z with four-bolt round-top carbs. I am rebuilding both carbs. I was told by a number or sources that the Walker 15566 was the right kit. Imagine my surprise when I compared the provided float needle and seat to the original. It was about 0.25-inches shorter than the original, or at least the one that has been installed for at least 20 years! The shorter assembly would not allow the float height to be set correctly.

Is this the wrong kit or am I missing something? I did pick up some OEM braided hoses for the connecting the float bowl to the body of the carb. Can anyone confirm that the originals were in-fact braided?

Where do I go from here?

Dann

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@siteunseen Cliff is the expert on needle valves. The hoses from the float bowls to the nozzles were not braided as I recall. The hoses need to be SUPER FLEXIBLE (think al dente pasta) otherwise the hoses will bind the nozzles, usually preventing the nozzles from sliding up (returning) to the unchoked position. Ztherapy supplies very nice hoses that I believe are made of silicone.

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Here's the hoses you can get from Nissan. I bought these a year or so ago. Maybe they're still available? Zcardepot.com has them also. They definitely aren't braided.

My needle valve advice from Bruce  at ztherapy.com was to stack those small washers to get the height you need. All those pics are on my laptop. I can post up what I have later today. Cliff

20191010_041345.jpg

 

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@siteunseen @Mark Maras

Thanks for your responses. I can tell that the braided hoses I have from another source are not right. They were actually too large for the original hose clamps, although I was able to get them on with some help from a needle nose pliers. I will get some proper replacements.

I think I have moved to either getting the ZTherapy rebuilt kit or have them do it for me. That's been a bit of a dream for 20 years! (About the last time the updated the look of their website! Good information, old design.) 

Finally, while the suggestion is logically sound, there is no way that I could add enough washers to position it correctly. The difference is greater than the length of the threads on the valve.

-Dann

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 If you want to have a go at refreshing your SUs get Ztherapy's video "Just SUs" along with your rebuild kits. You'll be an SU expert.

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I rembered something from a few years ago. Ztherapy set me some valves that were way short. I called Bruce and he said they most likely were Datsun Roadster valves. Overnighted them from California to Alabama. Fantastic customer service. 

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I will share what I know that might be relevant to your problem.

1) Your car year and the fact that you have 4 screw carbs should mean that you have the float bowl lids with the short ears that the pin slides through to hold the pivoting float assembly. You should have short needle jets in both carbs that are 25.25mm long (measuring from end of threads to end of body...(not including the actual needle that moves in and out of the body). In 72, Nissan changed this so that the front carb uses a longer needle jet (27mm apx) and longer ears on the float bowl lid; the rear carb is the same as the earlier 4 screw carbs. So, it doesn't really make sense that the shorter needle jet wouldn't work on your carbs. They should both be short...front and rear. Questions that come to mind are....

- is the needle jet in your rebuild kit shorter than 25.25mm? If so then maybe it is the wrong kit?

- Could your carbs have been swapped with long ear float bowl lids? I personally don't like trying to make the long ear lids work with the short needle jets. I have never been able to add enough washers to work before running out of threads to securely hold the needle jet in place.

2) Personally, I have never been able to get the long ear lids to work reliably. On my 72, I swapped the front lid with a short ear lid from another set of carbs. My recollection is that the lids will interchange regardless of 4 screw or 3 screw. So, on my 72 I run short ear lids and short 25.25mm needle jets. The problem I have with the long ear configuration is that it places the float lower in the float bowl chamber. In my experience this causes the float to hang on the side of the float bowl as it rotates through its motion. The result is a needle jet stuck open and overflowing bowl. I also don't buy into the engine angle argument that resulted in the change to a longer ear in the front carb and thus the changed fuel level measurements described in Technical Bulletin TS73-10. I subscribe to, and many disagree, the method of setting floats where you equalize the fuel level directly at the nozzle tubes with the mixture nut turned 10 full turns down (bigger topic but if you are interested, search and you will find lots of discussion about this method).

3) Finally, I will offer that I have found it really important to make sure the shape of the metal tab that you bend in order to set the float level is relatively flat and not overly curved. The new aftermarket needle jets are thinner than the original ones. Because of this, they get hung on the tabs if the tabs are curved too much.

Whatever you do, I think it is really important to spend the time getting the float levels set right. If they are not set right, you will find you can't get the carbs adjusted at or near the 2.5 turns down of the mixture screw. If you find you need 3.5+ turns or 1 turn or the mixture screw turning doesn't elicit any effect, it is a good sign that your floats are not set right.

 

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3 hours ago, Mark Maras said:

 If you want to have a go at refreshing your SUs get Ztherapy's video "Just SUs" along with your rebuild kits. You'll be an SU expert.

This is a very good option as I would like to retain the original carbs and don't need the "high gloss" of ZTherapy's re-manufactured units. (As beautiful as they are.) In addition, it it much less expensive.

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One thing Ztherapy does that is sort of impractical for most of us to do ourselves is they replace the bushing in the carb bodies that the throttle shaft passes through. On worn carbs, the old bushing becomes a vacuum leak...making it very difficult to get consistent adjustment. So, you might want to test yours for leaks. You could raise idle to say 2500 rpms and spray starter fluid where the shafts enter the carb bodies. If idle changes you might have a leak. Not sure if you can send the bodies to ZT and have them just do the bushing work but might be worth asking.

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1 hour ago, jonathanrussell said:

I will share what I know that might be relevant to your problem.

1) You should have short needle jets in both carbs that are 25.25mm long (measuring from end of threads to end of body...(not including the actual needle that moves in and out of the body).

1.1) Could your carbs have been swapped with long ear float bowl lids? I personally don't like trying to make the long ear lids work with the short needle jets. I have never been able to add enough washers to work before running out of threads to securely hold the needle jet in place.

Whatever you do, I think it is really important to spend the time getting the float levels set right. If they are not set right, you will find you can't get the carbs adjusted at or near the 2.5 turns down of the mixture screw. If you find you need 3.5+ turns or 1 turn or the mixture screw turning doesn't elicit any effect, it is a good sign that your floats are not set right.

 

I measured the length of the needle jets. The rear is 1.1" or 27.94 mm. The front is 1.0" or 25.4 mm. Given the crude old tool I'm using to measure and my "great skill ;)" is strongly suspect that they are both the same length and in the ball park of the 25.25 mm that you reference.

The replacement is 1" or 25.4 mm. That seems like the same length, but if you look at the pictures you will see that while the total length is the same, but the body vs threads are very different.

I measured the towers and they are all about .58" from the top ridge of the lid to the top of the tower. Same front and back.

I've added some pictures, including the heat shield which, based on the photos on ZTherapy site, this is the earliest form. I also show the jets. The one on the left is the original. Note the 1.7 on the barrel. You can see that even though they are the same, there is a big difference in the body vs the threads between the two.

Just for reference I also included two pictures of the tops with the float installed. Don't expect that they will be very helpful, but I include them just in case someone sees something that I am missing.

-Dann

Float Front.jpg

Float Side.jpg

Heat Sheild.jpg

Valves-Orig. on Left.jpg

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1 hour ago, jonathanrussell said:

One thing Ztherapy does that is sort of impractical for most of us to do ourselves is they replace the bushing in the carb bodies that the throttle shaft passes through. On worn carbs, the old bushing becomes a vacuum leak

You are right, what they do beyond a rebuild kit adds a lot of value. I have a very tough decisions. My history with rebuilding carbs on motorcycles many years ago is not too glorious. So, maybe I should turn it over to the pros. It would be great to know that the carbs I install are balanced and set to go.

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Here are some measurements for you. I opened up my 72 3 screw carb set from my 24k mile 240z I am refreshing. I don't think these carbs have ever been touched. They even have the original needle jets.

Anyway, the front carb has the caps with the longer ears. The length of the front cap ears from cap to the end of the ear is approximately 18.1mm or .7125 inches. The length of the front cap ears from the cap to the approximate center of the pin hole is 14.15mm or 55.70 in.

The rear carb has the cap with the shorter ears (same as what your 4 screw carbs should and do have both front and back). The length of the rear cap ears from cap to end of the ear is approximately 12.78mm or .5035 inches (consistent with what you measured). The length of the rear cap ears from the cap to the approximate center of the pin hole is 8.52mm or .3355 inches.

 

So here is what I think and others can weigh in as to whether I am understanding correctly. You have 4 screw carbs that have the correct float bowl lids with the short ears (or towers) both front and back. The problem is, someone installed a needle jet kit at some point that is for a 72 carb setup so your rear carb has a long needle jet and a short ear lid....which will / should never work. I think that if you install two short needle jets and set the float levels you should be in business.

Wells makes rebuild kits and they sell short or long needle jets. If my notes are correct, CK749 is the short needle jet kit. You could also just order needle jets from ZT because I think all they sell is short.

If I remember and understand what you wrote above you are struggling to install a short needle jet on the rear carb. What the prior owner probably did is severely bend the adjustment tab to force accommodate the long needle jet. So, you may need to do some tab reshaping. Use your front carb cap tab as a guide.

 

Hope this helps.

 

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Just remember even fresh Ztherapy carbs need some tuning to be right. they come pre adjusted but sometimes they need to be tinkered with.

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4 hours ago, jonathanrussell said:

If I remember and understand what you wrote above you are struggling to install a short needle jet on the rear carb. What the prior owner probably did is severely bend the adjustment tab to force accommodate the long needle jet. So, you may need to do some tab reshaping. Use your front carb cap tab as a guide.

So should the tab be above the "armature?" By armature I mean the body of the pressed metal tab and by above I mean closer to the lid. It was above when I took it out, but in my attempts to set it correctly, I pulled it down substantially and below the rest of the tab.

My measurements and comments about the length of the nozzle was not very clear. I am not very good with "fancy" measuring tools. So I took out a good ol' metal ruler and alighned everything. It gives you a much better picture of the difference between the two nozzles.

Thanks again for you help,

-Dann

Ruler Nozzles 2.jpg

Ruler Nozzles 1.jpg

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7 minutes ago, Patcon said:

Just remember even fresh Ztherapy carbs need some tuning to be right. they come pre adjusted but sometimes they need to be tinkered with.

I'm sure they do. I have to tools to tweak them as needed. These were just very difficult to adjust to begin with. The biggest problem was that I could not get the body nozzle to level with the bridge on the front carb. I simply could not turn the adjusting screw up high enough. So we removed the carbs to take a look. It was never my intent to attempt a rebuild. I found the reason for the initial problem, some bent washers were preventing the full range of adjustment. But, since I had them off.... Probably should have left well enough alone and reinstalled them at that time!

My expectation is that if I get the right kit, especially from ZT, I can probably get it together. OTOH, the car is 49 years old and treating it to a professional rebuild may be the thing to do.

-Dann

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1 hour ago, DannDZ said:

So should the tab be above the "armature?" By armature I mean the body of the pressed metal tab and by above I mean closer to the lid. It was above when I took it out, but in my attempts to set it correctly, I pulled it down substantially and below the rest of the tab.

So, the drawing below shows you how the tab should sit in relation to the metal float arm that attaches to the float cap ears. With the orientation shown in the photo it curves a bit above the parallel line of the top of the float. In the drawing, if a long needle jet were installed, either the tab would be drastically bent down OR the float arm would be bent and the travel possible for the float would be severely limited.

Also, regarding your measurements. I can tell that your short needle jet is about 1" which is about the same measurement I am getting in MM...what I wrote above- 25.25mm.

I agree with what Patcon said. ZT carbs come to you in great shape and I would say decently adjusted. The carbs I have received though (two sets) have benefited from more careful adjustment of the float levels. Don't get me wrong though...they do awesome work.

Hope this makes sense and helps.

 

float drawing (Small).jpg

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11 hours ago, jonathanrussell said:

the drawing below shows you how the tab should sit in relation to the metal float arm

Yes, that is the tab I am referring to. I think I need to do some more research into setting the float level. I'm calling ZT today. Still trying to determine if I want to "spend big" and have them do it as right as can be done off the car, or attempt to do it myself with their kit.

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I remember - vaguely- when I had a similar situation . It was something about the long jet assembly was no longer available but I had a carb with the longer ears . I believe I just redrilled the ears to the proper height to match the pivot point of the shorter jet assembly! So I just moved the holes up for the pin and adjust 

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Both of his caps have the short ears and thus need the short, easily available, needle jets.

FYI, the long ones are available from a company named Wells. I think I purchased from Rockauto.

For those who have long ears though...I actually like madkaw's method....re-drill and use the shorter needle jets...OR locate a short ear bowl cap and replace. I just don't like how the long ear / long needle jet config works in the bowls.

I checked Rockauto. I am not seeing the same options I was able to order a year or two ago. But, the kits I ordered at the time were similar to this offering on ebay (see below) where the kit is for one carburetor but it includes two needle/seat bodies...one short and one long. You assemble the one you need.

https://www.ebay.com/itm/Carburetor-Repair-Kit-For-1972-Nissan-240Z-C158SV/173967875276?hash=item28814b1ccc&_trkparms=ispr%3D1&enc=AQAEAAADIKvsXIZtBqdkfsZsMtzFbFsbX3WcW5fmB%2Fx7ZbaZTyex8i7n1lQ38Wwv00fEvu8N9rCKQfFKON4NOQ3D8SmHNmA9jykbbq7wo13Cux%2BQpQ3L3ZF3gVbgO8vQKDrboxJ1C0IL4WhifbrVuv%2BruWod44VIrGRv0W8Y3jhtVPUlLpPcPJ8Mt3spoLlpiG7pEojg0tsI5QlxVSZAbdj6nX8aWti2H5zgmCzjZdfpI%2FvtdnTddUi8QHBH%2FCN847fCCi0C7dp1gldpOZFzndtTPHwHwqkQWLU9M3NnyRmNXuFiR9JDYvB0s%2FtUZnXwqTVUQAkILFugvcotpy455CcSX8qQUqBTtKIycchyAFPPOdX5WGwx3bt53OE9IOrX2QmbxujOoxs2HSSfUza7M%2BcNa5CgWfvyIatuLAv7fVy2Ss2jVIKAZ%2FglxKDQczdFSGy4Rlm1vSZVZ3%2Fvze%2FllamSoXKYwCF55BEqng977c6wt5x2%2B%2BFPkQ%2FGTH0nJhNO0u6gx%2B6vt%2BYZ4rwai6oaOYtPOTfdIh1IKeVFNobeM%2FpL8ub4SOpA9MfKsW%2BKzeHcT35APm5GBWp9%2BwaOKZ5suqp6807VdPtbMj8h24Fgf0QCJ7VdSnz5t1%2FCPU7QgoC9XackNd2Fn606d6qwqInQsH7xXkCXCPaMfgmU9XUVVixkCarpdO99N9SQSvR8YX6JUPyIXjuTV4QV6Oi5QK3BZ4zMv4mw031u6lRl7p6yogLknt8RCmdCmktQOPTG7XAM0%2FbLROPDSE1%2BJgJE%2FEi45FCQe2N5gbFm2Zxs1GAepj2rtNjaz87ucRlh7hrhrQn%2Bu14r53qb1IyfRCgWcukjEzfKyP4Bqvtl4YGinjBVrOKrTz%2Fc7%2BrmkcyZUp%2BU%2BnNMKuz1JsVao2fVBzI1lzqBElXPWM7y7F9F8mY47se362zX6W99XvqQn8NHnsa5eGOI3Or4ZcbJO4z2A4xGlk2NBL8XFAC%2FK%2B3q0RTu9v3icCbPNRMS6xASFQjK1va57IeVyjMybxyVAwHnEWYlkREG2vElt6C8CukkpTDLC%2BQSqPqJWnqplAnp&checksum=173967875276bd133e6b6a8147c0a38f7c54e304c2c3

 

Edited by jonathanrussell
additional info

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6 hours ago, siteunseen said:

Check your float tang too.  You don't want them bent up like ramps. 

Excellent insight. In fact, I talked with Bruce at ZTherapy today and he made the same point. 

The link is particularly helpful. I think it takes a bit of an artist to make a smooth curve like that. But one thing Bruce was clear about is that this is not rocket science.

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