new to me SU's

[nightowlZ]

I picked these up in Sumas, Wa this morning. Thought it was time to change out the flat top Hitachi's.

Now, will an amateur who has the ZTherapy video and rebuild kit be able to break his carb virginity, or is it best to send it to the professionals for refurbishing? (along with $600 US)

BTW, what would a set of these be worth? Roughly.

[=Enigma=]

I bought their kit and video. I haven't rebuilt the carbs yet because I'm still working in the suspension, but it looks to be fairly simple. I think the hard part will be learning to tune them using the unisyn device.

As for what they're worth, that all depends on the condition they are in, but based on the prices I've seen on eBay, I'd say anywhere from $75 to $150 for what you show in the pic.

[280~Master]

If you have mech. ability they are not that hard to rebuild. Just take your time with them and soakem in some parts cleaner first. The tuning part of it gets a little hard. Use the right oil in them tune them up and BAM you have a nice set of carbs. I would shine them up if I had them. 180, 250, 500, 1200 and buff them to a shine. Thats just my .5 cents.

[beandip]

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I picked these up in Sumas, Wa this morning. Thought it was time to change out the flat top Hitachi's.

Now, will an amateur who has the ZTherapy video and rebuild kit be able to break his carb virginity, or is it best to send it to the professionals for refurbishing? (along with $600 US)

BTW, what would a set of these be worth? Roughly.

First of all they are worth $100. + with the manifold. To start with I would just remove one dome at a time. Remove one of the domes and when you unscrew it then carefully lift it off. You will find a piston and a large spring . The spring is important because it controlls the rise of the piston , which inturn lifts the needle . This needle controls the fuel mixture. the needle is brass and soft so be gentel . Clean the piston of the black crud . WD-40 will remove much of it also clean the inside of the dome . Wipe a thin film of oil on the piston with your finger and reassemble all . Be vary careful with parts cleaner as it can desolve some of the important gaskets and parts. From here I would just install the carbs and see how they run . Now check the little fuel line that runs from the fuel bowl to the bottom of the carb to see if it is stiff and or brittle. if it is buy a new set. DO NOT USE VACUUM LINE for this . Parts store fuel line is not meant for this and is too stiff . Nissan or ZTherapy has the hose. The stiff hose will cause the nozzle to stick down and a VARY rich mixture be the result . Go to the TEC SECTION AND DO A SEARCH FOR ADJUSTING S U CARBS . There is a step by step on how to do it. Gary Save the $6 clams. these carbs are fitted at the factory so dont mix the parts , work on one at a time . my 2 ¢ Gary

[EScanlon]

I don't deal with carbs, but I have heard "these carbs are fitted at the factory so dont mix the parts" before. Keep the "front" carb parts separate from the "rear" carb, and additionally, apparently there is ~some~ difference between the front and back. Not sure of what it is, but I've heard it from knowledgeable mechanics.

If you mix them, expect to have problems no matter what anybody tells you.

2¢

Enrique

[jackboxxx]

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I picked these up in Sumas, Wa this morning. Thought it was time to change out the flat top Hitachi's.

Now, will an amateur who has the ZTherapy video and rebuild kit be able to break his carb virginity, or is it best to send it to the professionals for refurbishing? (along with $600 US)

BTW, what would a set of these be worth? Roughly.

to me the nice thing about those carbs is they look to be straight off a motor...not in a box all torn apart..

If your lucky, a nice cleaning is all you need to do, I see a lot of dirt built up on the intake side.

I would suggest getting the SU rebuild kit from nissan or ztherapy or motorsport, dont go the cheap route and just buy hose from the auto parts store, for those bottom nozzle hoses..if you do, they will harden and crack, and then leak (right on to your exhaust) very quickly, which could be a fire hazard.

these carbs are very simple to tear down, clean and rebuild. dont be afraid to do this part. the only tricky part is the tuning of the carbs once they are installed on the motor. if your good with SU's you can adjust them kinda close yourself, but to really do it right you need a air flow meter, to sync/balance them correctly. if you dont balance them, you could end up with a motor that is getting the majority of its power from 1 side.

there are many sites out there to help you do this rebuild/tuning job heres a couple...:

http://zhome.com/ZCMnL/tech/su.html

http://www.sportsimports.ca/archive/technicaltips/att06.htm

and some info from our own site here...

http://www.classiczcars.com/forums/search.php?searchid=195369

[nightowlZ]

thanks for the responses. i will order the kit and video tomorrow. the $600 can go towards the struts and springs.

$90, and a 1 hour drive would seem like good value.

[kenz240z]

The fuel hose on the rear carb looks like regular fuel line. If so, it needs to be replaced with the correct rubber hose that Gary mentioned. It also looks like fuel has been leaking out of the rear fuel bowl. Perhaps the gasket between the fuel bowl & the fuel bowl lid has deteriorated. If you decide to try running the carbs before a thorough rebuild you can make a gasket for the fuel bowl from gasket paper.

Check to make sure the fuel nozzles move freely. The fuel nozzle is at the bottom of the main carb body (it has the rubber hose connected to it). You should be able to pull it down a little over 1/4". It is common on carbs that have been sitting for a while for the fuel nozzle to be stuck. The only way I've found to get them out is to use a brass punch and tap the nozzle out. Unfortunately, this damages the nozzle and it will have to be replaced.

Also, make sure the suction piston in the dome moves freely. Remove the little oil dipstick from the top of the carb and dump out any oil that is left in there. Then remove the screws that mount the dome to the carb body. With the dome removed you'll see a large spring and the suction piston. Clean all the carbon from the suction piston, and clean out the inside of the dome.

It looks like you have the three screw '72 carbs. I think these carbs are basically mirror images of each other, but it would still be wise not to mix parts between them. When you get ready to rebuild them, do one at a time. That way you can refer to the other carb when it comes to putting it back together. Take pictures along the way if needed to help jog your memory, too.

The SU's are really pretty simple. When you get them on the engine, make sure to adjust the valves & check the timing first. Also, make sure the points are properly gapped, and that the cap, rotor, plugs (properly gapped) & plugwires are all in good shape. Replace any of these as needed.

The SU's are operated by changing vacuum conditions of the engine. If the valves are misadjusted or the timing is way off, the vacuum conditions of the engine will be out of whack and no amount of carb tuning will make up for it. So, tuning the carbs is the last step after making sure everything else is properly adjusted and in good working order.

[Carl Beck]

Hi nightowlZ:

I have slightly different advice... take it for what it's worth.

If you have the $600.00 spend it on the carb.'s. Learning to tune the S.U.'s can be fun and easy "IF".. you start with a set that is capable of being "tuned". Disassembly and cleaning, setting the floats etc. can be fun and easy - "IF" you start with a set that's in good condition to begin with.

Attempting to install, then tune a set that is loaded with all kinds of other problems, for your first time - will be frustrating if not self defeating.

Just looking at the pictures of the set you show - would give at least an indication that they are FAR from factory spec. in many regards, and they have already been molested by a less than proficient tuner. Believe me when I say that attempting to properly diagnose and correct three, four or five problems, all occurring at the same time - with a Set of SU's - when you are just learning about how they are supposed to operate, is NO FUN.

Leaks around the throttle shafts, bent or malfunctioning hardware, bent fuel metering rods, maladjusted floats, etc etc etc - will all effect any "adjustments" you attempt to make, and the outcome of the recommended "adjustments" will not be as described etc etc.

Anyone can "learn".... most people can learn more quickly if they work with someone that knows what they are doing and have experience doing it.... But if you are on your own, my best advice is to start learning how to adjust and tune - on a set of "known good" SU's. Once you have experience with a good base line, then you'll easily move on to dealing with more complex or compound problems.

Spend the $600.00 on the rebuilt SU's - save money on labor that you can do without so many compounding "what if's"... In the mean time you'll have a car running right that you can enjoy, instead of fighting with. Springs/shocks etc can all come after...

In either case, good luck.

Carl B.

Carl Beck

Clearwater, FL USA

[Ed]

Some good advice from everyone. Question is what do YOU want to do. Work on them yourself and learn? And spend some more money getting them working right. Or send them in and get a set of rebuilt ones. The one's from Z therapy look and work like new ones. From the springs to the screws everything. They will also replace that worn out throttle shaft with a stainless shaft on sealed bearings. This alone is worth the job. If your throttle shafts are worn then they will leak air (vacuum leak).

I opted to do the work myself (something I enjoy) it took me quite a while and I ended up sending the body of the carbs to Ztherapy to have the shafts replaced. Everything else I learned and did myself. If I had to do it again I'd probably do the same thing.

$.02

[Victor Laury]

My argument for the complete ZT spa treatment? You spend $600. You get back reliable, dead-on carbs that are also beautifuly restored. Sounds like a bargain to me.