Carb Setup.. | The Z Club of Great Britain
  1. The Z Club relies on the support of it's paid members - join the club or renew your membership here.

Carb Setup..

Discussion in 'Tuning & upgrades' started by TimW, Mar 19, 2017.

  1. TimW

    TimW 1978 UK RHD 260z

    Hi Guys,

    Me again smh!..

    This may well be a dumb question, but I’ve noticed something on my carbs. Forgive my terminology, I have a lot to learn, but when I blow down the fuel inlets of each carb float (Pic attached.. I think it’s called the banjo bolt) I notice a different resistance/air flow between the two, thus therefore assume a difference in fuel pressure/flow. It’s not huge, but quite noticeable. Both float covers were held so the inlet needles were fully open and neither needle sticks etc. Both had a good squirt of carb cleaner which made no difference.

    Although one float in the picture has been cleaned up externally, I didn’t take out filter plug or make any adjustments in that area, (except to the float level -pic below), thinking when in doubt best leave alone.

    My question is; Is this something I need to concern myself about? And if so, how does one go about getting the correct setting?

    I’m getting there...:). got myself a couple of SU publications and a lot of reading on the net, but so far on this one, I’m completely blind!. I’m guessing from the design and the fact that the bracket holds the plug in place that these are adjustable, but that’s about it.

    Attached Files:

  2. jonbills

    ZClub Administrator
    Staff Member Moderator

    So.. you're blowing through from banjo bolt to open needle valve?
    I'd assume there shouldn't be a difference in pressure. If the needle valves are the same size then I'd guess the difference is down to corrosion.
    But I think it would only matter if it is stopping the float chamber filling quicker than the fuel gets used.
  3. TimW

    TimW 1978 UK RHD 260z

    Thanks Jon,

    I'm blowing through with float cover in its normal orientation (as in pic) with the needle valve already open, not to open them, but with the cover/float removed from the chamber if that make sense.

    Yes, I was thinking the same, seems logical that both would be the same. Needle valves are the same size and I think it's filling ok, just uncertain.

    Attached Files:

  4. TimW

    TimW 1978 UK RHD 260z

    Well.. I took it apart and now know what that part of the carb is all about.. lol....

    and here's the results!...Spot on Jon, full of corrosion, thank you.

    Nearly done, marked my 23mm line on the float chambers, ready to fit tomorrow.. Suppose that's where the fun begins.. haha..

    Attached Files:

  5. jonbills

    ZClub Administrator
    Staff Member Moderator

    Well done - so do they both get the same results on the blow test now?
    looks nice without being blingy.
  6. Rob Gaskin

    Rob Gaskin Treasurer Staff Member Moderator

    It's satisfying sorting stuff like that.

    Next job is to get the air intakes balanced without that bit of plastic. ;)
  7. johnymd

    Z Club Member

    I would say the next job is to get the float levels spot on.
  8. uk66fastback

    Z Club Member

    What did you use to get them shiney like that? A Dremel? Some of those parts are TINY
  9. TimW

    TimW 1978 UK RHD 260z

    Thanks Jon, I’d thought about getting them vapour blasted at one point, but I think they lose their character. It’s nice to see a bit of shine, but agree not too blingy

    Lol Rob, Yes indeed.... The shim and cable tie has served its purpose well, but time for them to go. I think I’ve worked it out, took a bit of time, but I think it’s just set up. I shall find out soon!..

    I’m reading up on that now Johny. I’ve set the float when inverted to 14mm till it just touches the needle and marked/slightly scored the outside of the float chamber with a 23mm line from the lip of the float chamber. I was planning on doing the level test with the clear tubing from the base on the chamber, but I’ve just found something on the net that talks about running the tube from the chamber drain plug and testing the level whilst the engine is at idle. Reading it ATM, any thoughts?

    Fastback, I used a bench polisher with 4 and 6 inch wheels. I bought a couple of kits from First a good clean up with Jizer (I find that better than Gunk, easier to rinse off and doesn’t leave a residue), then a going over on the wheel with a mildly aggressive polish and wheel so as to leave a patina. I don’t bother with the chalk to remove polish residue that can gather in nooks and crannies, just a little bit of petrol on a cloth in places where it has amassed too much. The smaller parts I held with a pair of pliers gently against the wheel and used a mild polish with a mid range wheel to avoid grab. The softer/white polishing wheel has a tendency to grab on the smaller bits. I’m obsessive, so I think a Dremal would see me there for hours eradicating every bit of patina and going all blingy!..
  10. TimW

    TimW 1978 UK RHD 260z

    Getting there I think.. The main thing is to get the 260 back on the road for the Samuri Gathering.

    Jobs still left to do are checking valve clearances and timing... ikr, I should have done that before I took off the carbs!.. my excuse being waiting for decent timing light to arrive...

    I’ve identified the distributor and ignition type. It’s D609-56A 801 with Lumenition Optronic Ignition and have installed new NKG BPR6ES-11 plugs.

    I’m new to much of this, just reading, more reading and then a little doing If there’s anything I’m missing guys please let me know. Here’s what I’ve done so far to the carbs;

    Installed new SM needles with the collar level to the piston base (was level to the groove in the piston)
    Checked centring of the jets
    Adjusted the Starting Interlocks to .65mm using a .65mm drill bit
    Cleaned the filter plugs and filters.
    Adjusted floats to 14mm as above and checked needle valve condition.
    Checked ease/rate of fall on the pistons with dampers out (one was slightly slower that the other, but a good clean with carb cleaner sorted that)

    A couple of things I’m not sure about.

    I’ve adjusted the throttle screw on each carb so that I just feel the butterfly beginning to open and then dropped it back a smidgen. I’m aware of their function, but uncertain where they should be initially set on a fresh install.

    The replacement needles are SM which are slightly smaller in length (52.5mm) than the original needs (55mm) of which I can just about make out the letter ‘Z’ on the collar.

    The needle valves are both the same length (18.5mm), I’d seen this article about a shorter valve in the rear carb. ( under heading Float Valves). This is out of my depth atm, but wondered about peeps opinion of this article.

    RIDDLER Well-Known Forum User

    Well done Tim. The car was running great when you bought it from me - let's hope that after all this effort it runs even better! The carbs look great, and you deserve a good result when you fire her back up.
  12. Sam_C

    Z Club Member

    You sure it's not an "N"? I think the various 240 carbs used N series needles. (N27 etc)
  13. TimW

    TimW 1978 UK RHD 260z

    Thanks Sam. Yes, it's an N.. I can't make out any number.

    Durh!... I took me two pairs of glasses to magnify and then a few moments to cotton on that I was holding the needle vertically.. lol
  14. TimW

    TimW 1978 UK RHD 260z

    Thanks buddy, good to hear from you Riddler. TBH I’m not sure about getting it running better, more the case that I don’t mess up a good car!.. lol..

    Here’s a pic of it’s current state. Engine bay coming up a treat.. Checking the valve clearances atm, all good and true so far. :thumbs:..

    How’s your luck on the next purchase, any joy?

    Attached Files:


    RIDDLER Well-Known Forum User

    That engine bay is unrecognisable! Delighted you are looking after my old motor so well. As for the next purchase, viewed a Dolomite Sprint but rejected it. Have got my eyes on a Volvo P1800s in Cumbria but not viewed it yet and am trying to arrange a viewing of a Mk1 VW Scirocco Storm this weekend.
    Meanwhile am still enjoying my Rover 3500S - especially since I had the V8 engine totally rebuilt.

Share This Page