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Patcon

510 Su's

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How do you tell SSS carbs apart from regular 1600 carbs? I am rebuilding some small throat SU's for Cody's wagon but I was unaware  there was anything other SSS carbs...

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I restored this 72 510 back in the 80’s. I was able to purchase the SSS Head, manifold and carbs from my local dealer. I never noticed any special markings on the carbs. I just assumed they would be the same carbs as the 1600’s or 240Z with different jets maybe. The head was what was special.

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The only Hitachi SU carbs that came on a 510/Bluebird/1600 were specific to the SSS model and had 38mm throats — the regular 510 carb was a single Hitachi downdraft. There are other versions of Hitachi SU’s out there, like the 46’s found on the Z, and some 510 owners try to make these work as well. ZTherapy can help narrow down what you have: http://ztherapy.com/products/masterprices/master_price_list.htm

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1 hour ago, NVZEE said:

The only Hitachi SU carbs that came on a 510/Bluebird/1600 were specific to the SSS model and had 38mm throats 

I have a set of those. They measure roughly 36mm but might be 38mm. I saw on the Z therapy site where they seem to differentiate between the two, but I couldn't locate the difference...Maybe it is the float bowl drain location

5 hours ago, Diseazd said:

I restored this 72 510 back in the 80’s. I was able to purchase the SSS Head, manifold and carbs from my local dealer. I never noticed any special markings on the carbs. I just assumed they would be the same carbs as the 1600’s or 240Z with different jets maybe. The head was what was special.

I have a head I bought out of Australia. Will need some work but should be usable. I am hoping to get Eiji to help with that motor when we get to that point. On your SU carbs, it looks like the bowl overflows are pipe away in hard lines to avoid the exhaust. Is that correct? I have two hard lines that came with the carbs and I assuming that is what they are for. Dumped onto the ground...

Guy, also how did you handle the chokes and throttle linkage?

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Those overflow lines are hard to find these days but worth installing for safety sake. This doesn't seem to have been as much of a concern on the Z. Anyone who's seen these puke fuel from a stuck float might think otherwise :o

Also, a few more details from this thread:

 

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54 minutes ago, Patcon said:

I have a set of those. They measure roughly 36mm but might be 38mm. I saw on the Z therapy site where they seem to differentiate between the two, but I couldn't locate the difference...Maybe it is the float bowl drain location

I have a head I bought out of Australia. Will need some work but should be usable. I am hoping to get Eiji to help with that motor when we get to that point. On your SU carbs, it looks like the bowl overflows are pipe away in hard lines to avoid the exhaust. Is that correct? I have two hard lines that came with the carbs and I assuming that is what they are for. Dumped onto the ground...

Guy, also how did you handle the chokes and throttle linkage?

Sorry Patcon....I don’t remember much about the linkage other than it wasn’t a problem.....pretty much worked with what was there. NVZEE is right about the overflow. I fired up a new Z engine once....some trash had the float valve stuck open. I sometimes fire up a new engine with open headers....that time I didn’t....lucky, it dumped quite a bit of gas into the air cleaner and onto the floor. I always hook up all exhaust before firing up now. 

BTW....I do remember that I built the engine with an L18 block and crank. L18 cranks are fully counter balanced...not so the L16’s....plus they are bigger:D

It was a fun little car....one of those you wish you hadn’t sold. :angry2:

Edited by Diseazd

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Here's a linkage diagram if you need it -- connects to the existing throttle rod. Choke's similar to the Z with a pair of cables attached to a single knob under the dash.

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I'm working on a set of SSS 38mm carbs from Z Therapy for my 510 project. 

These even have air bypass idle control and idle mixture control. Pretty advanced for the day. 

The flat tops in this case have no resemblance to the 73-74 Z carbs. Other than the air by pass hardware, they are just round tops with, well, flat tops....

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Sounds like later-issue carbs with some smog bits — maybe 610SSS? Did you modify anything or plan to run with the extra vacuum lines?

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1 hour ago, zKars said:

I'm working on a set of SSS 38mm carbs from Z Therapy for my 510 project. 

These even have air bypass idle control and idle mixture control. Pretty advanced for the day. 

The flat tops in this case have no resemblance to the 73-74 Z carbs. Other than the air by pass hardware, they are just round tops with, well, flat tops....

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Now that’s some beautiful jewelry......I think my wife said she would like jewelry for Christmas! :wub:

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2 hours ago, NVZEE said:

Sounds like later-issue carbs with some smog bits — maybe 610SSS? Did you modify anything or plan to run with the extra vacuum lines?

These carbs are quite advanced, carb wise. They have two "new" circuits compared to what we Z folks know about our "Round top SU's";one for idle speed control, and one for idle mixture adjustment.

I guess technically they're overall design to improve mixtures throughout the operational range,, which affects the cars overall contribution to "smog", but none of this "stuff" detracts from performance. Quite the opposite. . 

These carbs have holes drilled into the throats in a very specific spot that connect the thoat to the outside world. AFTER the bridge where fuel is added, but BEFORE the throttle plates. Why? Well first, to provide an idle bypass circuit. Instead of opening the throttle plates to let some air/fuel into the engine to set idle speed, we leave the throttle plates closed, and provide a separate path, with an adjustable orfice screw, into the intake manifold to control idle speed. Gee doesn't the later and "better" EFI systems use this technique? Yup.. Who did it first? Well....

Further we can another feature where we can control the idle mixture. How? By adding additional air into the new idle mixture path. This will only lean out that mixture, so to control the AFR of this idle mixture we must design the needle diameters in the idle range to be "rich" then adjust it to what we want by adding air. Slick, huh? 

So yes, I will be hooking up these circuits on the 510. Maybe even add a idle air control valve so I get fast idle that decreases as the car warms up just like EFI. Imagine that. It will be about as close to EFI as carbs can come.

BTW, those crappy flat top 73/74 boat anchors that are the butt of our collective scorn, do these same cool tricks, plus more.... (I always cheer for the underdog ;) )

 

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Here are a few more pics of the air manifolds that connect the idle speed and idle mix plumbing.

The bowl vents also have their own tube on the manifold. They join and come to the outlet that is sticking straight up. You need to connect that to the air cleaner to put the correct reference pressure above the fuel in the bowl. 

The large (9/16)  ports that point toward each other are the idle mix that are not hooked up yet. A fresh air line, again from the air cleaner, feeds the upper large port, which then goes past the orifice screw, then down to that carb and over to the other. 

The smaller inlets are the idle speed bypass that are connected to the tube manifold, then runs into another adjustable orifice screw that feeds into the balance tube. 

 

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6 hours ago, zKars said:

The flat tops in this case have no resemblance to the 73-74 Z carbs. Other than the air by pass hardware, they are just round tops with, well, flat tops....

I disagree with that 1000%. The only significant differences between what you have here and the 73-74 carbs is the integral float bowl and the inclusion of a REAL choke. Other than that, those 38mm flat tops are conceptually identical to the Z flat tops.

So for all the folks who poo-poo the Z flat tops, but are drooling all over these things..... I got one word. "Hypocrite!"     LOL

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Diagrams are from the “Nissan Motorsports Schematic Catalog”, p.n. 99996-M8015. Carl Beck posted a pdf on his site:

http://www.jdmjunkies.ch/wordpress/2016-05-14/240z-nissan-motorsports-schematic-catalog-99996-m8015/

http://zhome.com/NissanMotorsportsSchematicCatalog.pdf

Edited by NVZEE

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I couldn't get to it...

and is that a pdf link, because I can't highlight it...

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Updated links. The first one is a host page for viewing online and Carl's zhome url is a download.

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Got these beautiful FLAT TOP carbs running on the 510 tonight.  They run SO well.  Took it out for a quick back lane romp and had TOO much fun. 

Here is proof of concept.  Note. The idle is happening with the throttle blades 100% closed.

I swear I'm going to get fake plastic hemi-spherical caps made that you can snap on your flat top bells so you don't have to be embarrassed every time you open your hood...

And no laughing at the roof rack or the mack-tack paint job....

 

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Edited by zKars
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12 hours ago, zKars said:

Note. The idle is happening with the throttle blades 100% closed.

I swear I'm going to get fake plastic hemi-spherical caps made that you can snap on your flat top bells so you don't have to be embarrassed every time you open your hood...

I know you know this already, but the idle is supposed to happen with the blades completely closed. That's one of the common ways that people who don't understand the flat tops screw them up.

As for being embarrassed when you open the hood, I've got a better idea. Do what I did. You've got a lathe, right?

ROUND TOPS!!!
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