Results 1 to 13 of 13

Thread: balancing SU's

  1. #1
    Registered User grannyknot's Avatar
    Member ID
    CZCC-26437
    Join Date
    Feb 2012
    Location
    Toronto
    Posts
    698

    Default balancing SU's

    Just got my Synchrometer/SK and took it out to see what the balance was like on my still shiny ZTherapy SU's, Well the lowest I can get the idle down to without stumbling/stalling is about 900rpm.
    At that idle the SK reading is up in the 18-19 kg/h scale, so no accuracy and almost impossible to see.
    Should I have bought the BK model with the air bypass? What am I doing wrong?
    Thanks,
    Chris
    1970 240Z HLS30 01955 March/70

  2. #2
    Nova Scotia,Canada,Earth Blue's Avatar
    Member ID
    CZCC-7641
    Join Date
    Jan 2005
    Location
    NS
    Posts
    4,085

    Default

    1. Turb each jet all the way up then turn each down 2.5 turns.
    2. Warm the car up.
    3. Disconnect carb linkage between carbs from the long rod that is parallel and next to the balance tube (just pull an end off the ball and socket rod connecting the two between the carbs.
    4. Make sure choke is off and jets are all the way up
    5. Use STE synch on carb one and set air using idle stop screw adjusting screw
    6. Use STE SK sync on carb two and set air using idle stop screw adjusting screw to match the flow on carb 1
    7. Repeat until the same and you are happy with the idle.
    8. Reach in and lift the piston on carb one all the way up. This disables carb 1 and makes the car run on the back carb only.
    9. If car can not run turn the back carb jet down a 1/4 turn and try step 8 again. Repeat 9 until the car can run . You may have to turn the jet up.
    10. Set carb 1 to the same number of turns down that carb 2 ended up at.
    11. Repeat but run the engine on carb 1 by lifting the piston in carb 2 all the way up. Adjust the jet on carb 1 by no more than 1/4 turn up or down to run.
    12. Rebalance the air flow as done in steps 5 & 6.
    13. Reconnect the throttle linkage and turn the screw near the middle of the bar near the balance tube. This will increase the RPMS (off idle). Use the STE Sync tool so that carb 1 reads 30 or 35.
    14. Adjust the screw on the linkage to the left of carb 2 and measure the air flow. Adjust so that carb two is also 30 or 35 (depending what your target was on carb one).
    15. Unscrew the screw near the middle of the bar near the balance tube so that the carbs go back to idle



    I can ring and walk you through it if you want.
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


    John Ruskin (1819 - 1900)



    ZCars in Eastern Canada seaport ready for shipment to Europe

    http://ZSportCanada.com


  3. #3
    Registered User siteunseen's Avatar
    Member ID
    CZCC-24724
    Join Date
    Jul 2011
    Location
    Alabama
    Posts
    1,967

    Default

    Here's what I've come up with. Yeah it's a toilet flapper but it's new.
    Attached Images Attached Images  
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

  4. #4
    No more body roll! SteveJ's Avatar
    Member ID
    CZCC-5413
    Join Date
    Dec 2003
    Location
    Gainesville, GA
    Age
    54
    Posts
    3,651

    Default

    Quote Originally Posted by siteunseen View Post
    Here's what I've come up with. Yeah it's a toilet flapper but it's new.
    I dunno. It looks like something that might be more appropriate on an adult toys website.
    73 240Z
    74 260Z

    Blue's collection of tech tips - A great place to look for answers
    XenonS30 -The cheap source for FSMs
    Georgia Z Club
    Fiddling with Z Cars - Z car tips & tricks and pictures of my car-loving life.
    Steve's CARtography - Just car pictures.

  5. #5
    Registered User Gary in NJ's Avatar
    Member ID
    CZCC-21253
    Join Date
    Mar 2010
    Location
    Amongst the twisty roads
    Posts
    1,057

    Default

    Blue,

    One more step to add...

    16. Get out Colortune (or similar device) and match the flow based on combustion.

    Like many on these forums, I've been using a synchrometer for 30 years. And I've always got good results. But a few years back I decided to spend $25 and try a colortune. Now I get great results. From what I understand there are better devices then a colortune as well.

    The synchrometer gets me 90% there, but matching the combustion puts me right on the money.
    Gary
    Guardian of HLS30-91415
    Previous Owner of a 10/70 240Z ('83-'85)

  6. #6
    Nova Scotia,Canada,Earth Blue's Avatar
    Member ID
    CZCC-7641
    Join Date
    Jan 2005
    Location
    NS
    Posts
    4,085

    Default

    Yup. a/f is important. I use an O2 in the tail to get the A/F balanced when running on a single carb. In steps 8 to 11 I set the A/f to ~ 27 to 30 for each carb by adjusting the jet on the working carb. I then go for 14-15 at idle. Anything else requires piston weight and spring changes...and/or needle re-profiling.
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


    John Ruskin (1819 - 1900)



    ZCars in Eastern Canada seaport ready for shipment to Europe

    http://ZSportCanada.com


  7. #7
    Registered User Stanley's Avatar
    Member ID
    CZCC-24191
    Join Date
    Apr 2011
    Location
    Redondo beach
    Posts
    641

    Default

    Also the initial turns down on the nozzles depends on temperature and altitude per the graph in the FSM. Using an IR thermometer helped me get the about the same A/F on each cylinder, but you need to take a lot of readings and average them - that doesn't take too long though. Reading the plugs gives a ballpark A/F. In my planes (in the game FSX) you set A/F using the EGT gauge. Problem with the colortunes (want to get one, though) is you can't read it under load at WOT. Maybe all you really need is 6 into 2 headers with a wideband for each secondary pipe, and an EGT on each primary close to the exhaust port. Would that be too many gauges? Colortune, IR, and reading the plugs, and butt dyno is way cheaper though. Oh yeah, and a stopwatch or dragstrip.

  8. #8
    Casey H Casey_z's Avatar
    Member ID
    CZCC-21264
    Join Date
    Mar 2010
    Location
    Smithville Ontario
    Age
    67
    Posts
    207

    Default

    Hey grannyknot

    I take a spin down to see Laverne in Kitchener everyother spring.

    He does use a colour tune.

    He has my Z running great.

    I get wanting to do it yourself but I can't argue with success

    Casey
    Last edited by Casey_z; 08-18-2013 at 07:11 AM.

  9. #9
    Nova Scotia,Canada,Earth Blue's Avatar
    Member ID
    CZCC-7641
    Join Date
    Jan 2005
    Location
    NS
    Posts
    4,085

    Default

    Reading plugs is always a good learning experience. You can do it at idle... just try idling for 5 min at 1.5, then 2.5, then 3.5 the 4.5 turns for each setting. Read the middle plug for each carb (plugs 2 & 4) and watch the colour change. Both plugs should get darker and should be identical if you have the jet heights and needle to piston fit correct.

    btw I set the air fuel on my oil fired furnace eyeballing the flame colour. A year later i had it tested and was within 2% so the principal of colour-tune is sound...however it only sets idle. You really need an O2 sniffer for checking idle, cruise and WOT (if you want to try to adjust these for performance or fuel efficiency or for the best compromise). The SU's are designed for set and forget so colour tune should be fine for daily driving.
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


    John Ruskin (1819 - 1900)



    ZCars in Eastern Canada seaport ready for shipment to Europe

    http://ZSportCanada.com


  10. #10
    Registered User grannyknot's Avatar
    Member ID
    CZCC-26437
    Join Date
    Feb 2012
    Location
    Toronto
    Posts
    698

    Default

    Blue and all, thanks. Lots to digest. Our local Zfest is next weekend so I don't want to screw around with it too much as the car is running fairly well at the moment.
    After Zfest I'm going to switch back to the SK triples that came with the engine to see if there is a power gain to be had.

    Blue, I'll take you up on your offer, I'm pretty sure I have the triples set up correctly but will probably need help.
    If the triples prove to be too finicky for me I'll be heading back to the SU's.
    Chris
    1970 240Z HLS30 01955 March/70

  11. #11
    Nova Scotia,Canada,Earth Blue's Avatar
    Member ID
    CZCC-7641
    Join Date
    Jan 2005
    Location
    NS
    Posts
    4,085

    Default

    I'll do my best to help remotely
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


    John Ruskin (1819 - 1900)



    ZCars in Eastern Canada seaport ready for shipment to Europe

    http://ZSportCanada.com


  12. #12
    Registered User Gary in NJ's Avatar
    Member ID
    CZCC-21253
    Join Date
    Mar 2010
    Location
    Amongst the twisty roads
    Posts
    1,057

    Default

    Quote Originally Posted by Blue View Post
    the principal of colour-tune is sound...however it only sets idle.
    Not true. I set idle, and then I check everything with a fast idle (3,000 rpm). Generally after slow idle is set, any change for fast idle is in the 1/16 to 1/8 turn range.
    Gary
    Guardian of HLS30-91415
    Previous Owner of a 10/70 240Z ('83-'85)

  13. #13
    Nova Scotia,Canada,Earth Blue's Avatar
    Member ID
    CZCC-7641
    Join Date
    Jan 2005
    Location
    NS
    Posts
    4,085

    Default

    I just did quick and dirty set-up of a 260z yesterday and set the air into each cab to "9.5" on the ste sk gauge at idle. Not sure of the rpms.
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


    John Ruskin (1819 - 1900)



    ZCars in Eastern Canada seaport ready for shipment to Europe

    http://ZSportCanada.com


Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Corner Balancing
    By gnosez in forum Suspension and Steering (S30)
    Replies: 1
    Last Post: 01-01-2009, 04:32 PM
  2. Balancing and blueprinting...what are they doing?
    By gogriz91 in forum Engine and Drivetrain (S30)
    Replies: 20
    Last Post: 12-10-2005, 10:11 AM
  3. Engine Balancing?
    By Ed in forum Engine and Drivetrain (S30)
    Replies: 4
    Last Post: 01-27-2003, 09:41 PM
  4. Balancing the rods
    By Ed in forum Engine and Drivetrain (S30)
    Replies: 10
    Last Post: 08-15-2002, 07:19 PM
  5. balancing an engine....
    By 71datsun240z in forum Open Discussions
    Replies: 2
    Last Post: 06-08-2002, 11:13 PM

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •