which needle?

[julioenr0103]

Hi, I just finished fixing my SU carbs on my 280Z on a L26 engine, yes quite a tuttifrutti of a car jajajaja, anyways on the way of fixing the carbs(late 240Z i guess) i wasn't able to save the needles and never got the chance to run them. I was wondering what type of needle should I put on, it is a manual transmission and a L26 engine...

[=Enigma=]

No ideas on the needle but I know someone is gonna ask.....are you running the stock flat top carbs or have they been replaced with round tops. Someone might be able to help you with the round tops but I'm not so sure about the flatties.

[Ed]

Someone might be able to give you a "ballpark" suggestion. But to accurately tune the carbs and install proper needles you will need to analize the exhaust gas. The entire engine needs to be in tune also.

[beandip]

Why were you not able to save the old needles ?? Are these Round top SUs ? If so , is there three screws or four holding down the dome ? What is the casting numbers on the intake ? I am asking these questions because , if you have a setup with 3 screw carbs and you remove them with out draining some coolent down to below the level of the carbs . You will be dumping coolent into your cylinders . When you were doing what ever to the carbs , I hope you dident mix up the parts especially important with 3 screw units but important in any event . These carbs were fitted and matched at the factory . As Ed stated to properly tune the carbs the rest of the engine's adjustments must be correct . Timing , and valve adjustment. I personally am running a 280ZX engine in my 240Z with round top SUs . I live at an altitude of aprox 300' . So far I have found the F-54 needles to be correct . I havent had the opertunity to do a run on a dyno as yet , but all indications seem to point to this setup . If the old needles were touching or rubbing the nozzle then they should be replaced . 3 screw units only align the needle from the movement of the dome that sits on the cone shaped projections on the body and these projections are what is set at the factory on each individule unit . This is why it is important not to mix up the parts from one carb to another. The four screw carbs have an adjustment for the nozzle under the carb in the holder. The performance of either type of carb is the same so either will provide the same HP if set correctly . From what the engine builders I have consulted with , race guys , the SUs will make greater low end power on a 280 engine . Emissions may be a problem though. Hope this helps . Gary By the way if you live in a high altitude area F58 are leaner.

[julioenr0103]

after some research I think I actually may have the early carb, not the flattops, which by now I know I dont have.there are 4 screws per dome. The needles where bent because the piston was stuck so hard at the dome that while trying to pull it out in both cases the needle faced a hit or two, one even strucked the ground (the whole piston) OUCH!!, the jets where also stucked, but finally I made the whole thing work again, thanks to some muriatic acid and heating...yes powerful. thanks to my local nissan dealer which knows nothing about carbs I was stuck with the only needle they found (N 27) and hope that when it arrives I'll be able to test it and see if it works at least and then work from there to a better needle but in a somewhat far future (expensive stuff 48 bucks!!). as by what I'm finding through my (relatively new) Z is that it was completely forgotten, sad...

[kenz240z]

Sounds like your carbs could use a rebuild. Have you considered Z Therapy? They can totaly rebuild your carbs and make them look & perform great.

www.ztherapy.com

[beandip]

after some research I think I actually may have the early carb, not the flattops, which by now I know I dont have.there are 4 screws per dome. The needles where bent because the piston was stuck so hard at the dome that while trying to pull it out in both cases the needle faced a hit or two, one even strucked the ground (the whole piston) OUCH!!, the jets where also stucked, but finally I made the whole thing work again, thanks to some muriatic acid and heating...yes powerful. thanks to my local nissan dealer which knows nothing about SOUNDS LIKE THE CARBS YOU HAVE ARE IN BAD SHAPE AND NOT MUCH GOOD. Insted of dumping cash into these start looking for another set , the 27 needle is a rich needle used on the '70 240Z in some applications . You are faced with spending money here . At least $100. for a used pair of round tops. These carbs are vary simple in design but they do have tight tollerences and if they are coroded to the point that they had to be forced apart as you said , not likely that they are useable. Ztherapy has rebuilt carbs for around $500.00 + a set. :disappoin YOU NEED TO MODIFY YOUR PROFILE AND INCLUDE WHERE YOU LIVE . SOME ONE MAY BE ABLE TO HELP YOU FIND WHAT YOU NEED

[julioenr0103]

thanks for the advice, I actually thought the same for the carbs on replacing them for another used set, Z therapy is just way too expensive for my wallet, the whole car was even half the price of a set of rebuild carbs. Anyone knows about a yunk yard that has 240Z's in texas particularly around el paso so I can start searching for a usable set?? thanks for all the help

[Bruce Palmer]

Boy, is this pricing thing all relative or what? Was talking with a friend of mine the other day who happens to be going through a roadster at the moment and he told me it costs about $1800 for the front end parts for a Datsun Roadster these days. That's just parts!! $200 for ball joint make a set of $600 carbs look pretty cheap. Oh well......

Happy New Year Y'all

[jjones-lg]

Your carbs are okay and the N27 will work just fine. Last I heard the N27 wasn't available anymore but glad to hear you found some. As long as you can get the pistons to move up and down freely in the dome you'll be okay. Mixing up the dome and pistons can cause you some alignment problems but that's not the end of the world. You can loosen the sleeves that the nozzle slides in and realign it. I'd recommend you get some new nozzles as long as you're at it.

There are a couple of tricks to mixing and matching the SU parts but it can be done. First when aligning the nozzle sleeve remove the adjuster nut (device) and spring. Then loosen and remove the sleeve and the aluminum washer at the top of the sleeve. Throw away the washer because if you reinstall it you will never get the sleeve aligned (that’s the trick!). The washer gets a kind of groove in it and will miss align the sleeve every time you tighten it. Install your needles and if you have the late model with the slot in the bottom of the piston set the shoulder of the needle to the bottom of the piston (where it contacts the ramp). Next install the dome, spring and piston on the carb and tighten the screws. Now put the sleeve and retaining nut back on the bottom of the carb making sure to use thread lock on the sleeve-retaining nut. Now with the piston on it’s side gently tighten the sleeve-retaining nut. I continually push the piston open and let the spring return it, listening for the clunk as it bottoms out. Remember that this is all done without the mixture adjusting nut and spring. Once you have the retainer snugged (you don’t need a ton of force here) make sure the piston moves freely and you can hear the clunk as it seats.

As for mixing the different parts you have to be careful about the needle valves. The early or late (don’t remember off hand) have different length valves. You can mix and match the nozzles between the 3 and 4 screw carbs. I can never remember which is which but on one you have to set the needles to the upper step of the slot in the piston. I just set the needles closer to the nozzle and adjust at 2 and ½ turns down and if it’s too lean I know I have to reset the needles.

Seriously the N27 should be fine for the 280 unless you have a cam or something. There used to be a ton of Brit needles out there and I used the RH needle for years as a performance needle for a lot of applications. I’ve also fixed more than one set of carbs messed up by water damage. A little acid dip and you’re good to go.

You don’t need a completely restored carb to get something that will work. A carb doesn’t care if it’s concourse or not.

[Mark Maras]

My early 71 carb needles are about an eighth of an inch longer than the needles that came in the round tops in my 260. Sorry, I don't the age of the short needle carbs.

Mark in Portland, O