Cliff's 720 project

[mad uncle cliff]

Meanwhile - that salt trick really works.

 

 

Might wash the salt off in a day or so before it gets out of hand.

 

[mad uncle cliff]

So - I go to get my Weber and somehow I end up with these instead.

 

Lucky there was no guy offering to swap my cow for a handful of magic beans or i would be stuffed.

 

 

[wayno]

Your going to have to fabricate a throttle linkage for this SU assembly, I like them if they are serviceable, generally I have found that they were removed for a reason, them appear to have not been on an engine in a long time.

Do not touch the needle inside the throats, they are easy to bend.

Your also going to need a SU choke cable.

Edited September 15, 2019 by wayno

[mad uncle cliff]

Thanks Wayno,

 

I am thinking of getting a Datsun Stanza throttle cable to rod adaptor, I believe that the Stanza had them fitted on the firewall. Need to do some research.

 

Anyone got any advice on how to convert the SU's to cable throttle?

 

And choke cable for sure - I can just fit a choke in the spot already set aside in the dashboard.

 

Thanks for the tip on the needle, I will be careful. I have stripped and rebuilt a few motorcycle carbies and I have an ultrasonic bath cleaner so I will carefully pull apart, clean and rebuild these SU's.

 

 

[datzenmike]

There's a good chance this was on a low mileage import engine. Garages found it was cheaper to buy them up and swap in complete or even a head rather than the cost of machine work to rebuild them. Mixed in with the regular L16s and 18s were SU equipped L16SSS and L18SSS engines from 510 Coupes. As the SUs would not connect up to anything sent over here the intakes and carburetors were just thrown away, some were saved. I have a set of L18SSS flattops (no, not those flattops) on a 220 intake and the choke cables have been cut with a bolt cutter just like a wrecking yard would do when yanking an engine. Given the choice I would rather have the SUs than a weber.

 

The SUs are not the European SUs and are called SUs (Skinner Union) but they are not. They are Hitachi 'twin carbs' or 'side draft'.  They are similar in theory of use and looks but made by Hitachi, so if looking for information or parts go with the Japanese ones.

 

The difference in what you got vs. what you thought you were getting could have been what the seller thought it was. If all you have seen are L series carburetors and these show up you might think they are Webers if you don't know better. Caveat emptor... 'let the buyer beware' holds that it is the sole responsibility of the buyer to assure that he is getting what he is paying for. In this case I think you made out alright!

 

If converting to linkage from cable....

 

The old 1600 or 510 throttle is fixed length. This from a later 710, will extend towards the carburetor. The part with the hook just above the plastic handle will extend out and fit an SU manifold.

 

[mad uncle cliff]

Thanks Datsunmike - I did not know there were SU's and Hitachi SU's.

 

I did know what I was buying when I got these; I ran a 180BSSS with twin SU's in my Datsun 1600 back in the 80's. Easy fit then as all the linkages lined up.

 

And given the option of taking that 32/36 Weber or these SU's, like you I went straight for the SU's. These are also off a 180BSSS, or that is what we called that Datsun here in Oz.

 

Linkages - the thing is I can't buy any USA old parts as you all have the steering wheel (and therefore throttle) on the left so it won't work here on the right side.

 

(Nice thing about our right hand drive Datsun's is we don't have air filter clearance issues).

 

I am interested in what the cable throttle set up looks like on your flat tops - if you can share a photo that would be useful. I am looking at the way some of the British twin SU manifolds run a cable throttle bracket, maybe I can make my own if I can't find a cable throttle set up that fits these SU's.

 

[datzenmike]

I guess I was misleading. I have the SUs but didn't use them. Instead I build my own intake and run R-1 motorcycle carbs.

[wayno]

I made my own throttle assembly, I used a part off a hangglider for cable routing, drilled it so I could screw it on the bracket stock bracket I had modified(cut), I used this for over 10 years.

 

 

 

You can see I used a random piece of metal as a cable mount, I just mounted it and then twisted it around to where I wanted it.

 

This is one I did recently, it has a larger wheel/bell crank/pulley off of a carb as my pedal was sticky, it didn't help, what helped was turning the idle up a couple hundred RPMs.

 

 

[mad uncle cliff]

Thanks Wayno - that recent job looks spot on. Maybe I can scrounge the parts I need off a stock carbie and do my own fabricating magic.

[wayno]

I just use whatever is laying around, the way I did the first one was easier, but the wheel was small and it was harder to push the pedal, the second one I had other parts from another engine(the giant aluminum bracket), and I made a couple more pieces to align the cable mount, I threaded an all thread rod into the end of the hollow shaft mounted on the manifold till it would not go in any farther then I drilled the bell crank hole round and I mounted it on the threads left sticking out the end.

Here is another one I have.

 

I think simple is better, the fewer parts the better, of course I have been collecting parts for a long time.

Edited September 16, 2019 by wayno

[mad uncle cliff]

Got my SU's on the bench ready for a strip down and rebuild.

 

 

 

So - anyone got a link to an exploded view parts diagram so I know how to put them back together once I have cleaned all the parts?

 

[wayno]

The brass needles mounted on the bottom of the pistons that move up and down are delicate, they have a jig at Z-therepy to center them in the piston when mounting them, I also heard people say they can be bent just picking them up off a table with your fingers, I am not sure I would even touch them unless they looked really bad/dirty, then maybe gently clean them with a q-tip, you certainly would not want to touch them with you fingers while mounted in the pistons.

[mad uncle cliff]

On 9/23/2019 at 6:05 AM, wayno said:

The brass needles mounted on the bottom of the pistons that move up and down are delicate, they have a jig at Z-therepy to center them in the piston when mounting them, I also heard people say they can be bent just picking them up off a table with your fingers, I am not sure I would even touch them unless they looked really bad/dirty, then maybe gently clean them with a q-tip, you certainly would not want to touch them with you fingers while mounted in the pistons.

 

Good to know Wayno,

 

I will have a crack at cleaning these up once I find a decent parts diagram

[BrothersGarage]

On 9/14/2019 at 1:49 AM, mad uncle cliff said:

Talking to this guy on the phone , he has a lot of Datsun engine stuff lying about... 

 

Nice score, and time to make a new friend!

[]2eDeYe]

I found that motorcycle control cable is cheap and easy to make your own accelerator/choke cables with. You can buy sheathing, cable and all the fittings separately for pretty cheap. 

[mad uncle cliff]

13 hours ago, ]2eDeYe said:

I found that motorcycle control cable is cheap and easy to make your own accelerator/choke cables with. You can buy sheathing, cable and all the fittings separately for pretty cheap. 

 

Great idea!

 

Given the number of custom motorcycles I have built, why didn't I think of that?

 

I bought an old stock 720 carbie so I can scrounge the throttle cable linkage off it and fit it to the SU's. Hoping my stock 720 cable will then fit.

 

I do need to fit a choke cable, I have heard that you can do with just one SU on choke, rather than run a cable with a splitter.

 

PS - Still looking for a Hitachi SU parts diagram if anyone has one ...

[]2eDeYe]

I found this teardown of one. 

 

http://evilbocho.blogspot.com/2013/08/disassembling-of-hitachi-carburetor-for.html

[mad uncle cliff]

6 hours ago, ]2eDeYe said:

I found this teardown of one. 

 

http://evilbocho.blogspot.com/2013/08/disassembling-of-hitachi-carburetor-for.html

Thanks - but I need a twin SU guide

[mad uncle cliff]

Still mucking about with carbies...

 

Meanwhile I had a crack at fitting the old radio cassette unit I bought, but unfortunately it is too wide and I do not want to cut the dash to make it fit.

 

Anyone know where I might find a 720 radio cassette unit that I can fit in my stock dash?

 

Next Sunday is Datsunday show day here in Victoria so I will go to the show and take some photos.

 

[wayno]

OK, I am wondering if you have pulled the SUs apart yet, if not I would not touch them till I have tried them, they tend to be worn out when people remove them, yes the engine runs with them but they have issues.

Normally I would make sure the pistons move freely up and down the slides, then I would make sure the levers opening the butterflies and associated linkage also move freely, make sure the chokes move freely and don't get stuck, I myself use PB Blaster a lot on everything.

Then I would install them, close the fuel mixture on the bottom and open them both the same amount(3 turns?), I likely would count how many turns it took to close them and average them out evenly.

Next I would try to start it, if it started right away I would try to adjust it to a reasonable idle speed(800/1000/1200rpms), then I would balance the 2 carbs by looking at the floating pistons, I would adjust whichever one was open the most to the other one that was not as far open, if you have a flow meter then I would fine tune them after getting them close.

Next I would see if both were serviceable, I would disable one by lifting the floating piston without touching that needle, I just lift it from the edge, when the piston is lifted there is no vacuum so no fuel is sucked into the engine, then while holding the piston up I would start closing the fuel mixture screw on the bottom of the other carb till the engine dies/tries to die, if it keeps on running after the fuel mixture screw is closed then that carb is not serviceable and likely needs rebuilt, if it does die then I would restart the engine and I would open it up till the engine idles smoothly and if it would not die I then would open the fuel mixture screw back open to where it was when you started and then I would disable the carb you just adjusted and repeat what you just did to that carb.

If either carb keeps idling when the fuel mixture screw is closed then that carb is not serviceable meaning it needs rebuilt.

Keep in mind that I have ran my work truck engine for a few years with a set that one carb needed rebuilt/was not serviceable, but it didn't run like it should, but it ran and idled good enough, a few years later one of them carbs gave up and I could not do freeway speeds(it was missing), so I put another used set I had found/bought on the engine and them are what are on it now and have been for several years now, they are not great either but they are good enough for me, new carbs are better but I am lazy and have not sent a set off to be rebuilt(the set I removed).

What I just explained above is how I get an engine running, then I fine tune the fuel mixture so both carbs make this same kind of loping sound when I disable one and then the other, I am after the same loping sound so I know they are set the same, if it will not lope and keeps right on idling smooth then I open up both fuel mixture screws the same amount and drive it that way and then I start looking for another set of carbs that are good or can be rebuilt.

The first time I ever adjusted my SUs(new set from Nissan, clearance sale) I used some manual I had that I cannot find anymore, if I were you I would go to a used book store over there and try to find the book with the title "SU Carburetters Tuning Tips & Techniques", here is a link to one on Ebay in the US, the ones on the Australian Ebay are kinda expensive.

https://www.ebay.com/itm/SU-CARBURETORS-MANUAL-CARBURETTERS-TUNING-TIPS-TECHNIQUES-BOOK/223435523626?hash=item3405cb862a:g:9qEAAOSwz39dw3Tz

It goes into way more detail about how to tune SU carbs, so much detain it gets confusing sometimes, it actually very simple really, balance the carbs so both move at the same time when the throttle is pushed, balance the air flow(when running) with a flow meter, adjust each carb one at a time by disabling the other so they have the same loping sound without dying and your good to go, I personally fine tune them by spark plug color from then on, if the back 2 cylinder spark plugs/cylinders are black I lean it out(close the fuel mixture screws), if they are white I adjust it richer(open the fuel mixture screws), same with the front 2 spark plugs/cylinders.

 

[mad uncle cliff]

Wow Wayno - if only you were my neighbour!

 

The SU's are intact and will remain that way until I get around to fitting them by following your instructions.

 

 

[mad uncle cliff]

Mucking about getting the Datto ready for a couple of shows.

 

I had a few spare stickers and a boring looking steel panel riveted to the inside of the tailgate so ...

 

[mad uncle cliff]

Meanwhile that beautiful condition stock interior got a good clean and polish, and even though I have not found a stock cassette deck yet I could not resist installing the 1980's cassette holder.