RB30X Posted October 8, 2009 Share Posted October 8, 2009 Hi, I've just installed some 40mm triple webbers on my 240Z and put the twin SU's into the vault. The car starts and revs fine but I thought I would check and balance the air flow of each carb using a uni-sync, except when I place it over each carb it obviously restricts air into the carb and when you pull it away, excess fuel drips out.........all over the headers? How do you avoid that? I thought about installing a stainless heat sheild which would also catch the fuel but I'd rather no fuel end up outside the engine. Also, at idle these carbs seem to whistle or squeel a little, is this a webber related thing or could something be loose inside? cheers Quote Link to comment Share on other sites More sharing options...
yetterben Posted October 8, 2009 Share Posted October 8, 2009 My webers pull hardly and vacuum at idle. i mean like nil. They flow but not enough at idle for and measurable amount. What i do is set the linkage to hold 3,000 rpm. Then i set the 3 linkages accordingly. Check out the weber thread at the top of this page. I have 33m chokes. Quote Link to comment Share on other sites More sharing options...
wondersparrow Posted October 8, 2009 Share Posted October 8, 2009 I would check your float levels. Every time I have had fuel coming out of the horns it was because of the float levels or a vacuum leak. That being said, my car idles around 1200rpm, so balancing your carbs at slightly above idle is probably easier. Quote Link to comment Share on other sites More sharing options...
yetterben Posted October 9, 2009 Share Posted October 9, 2009 Fuel is gonna come out if you keep it on there long enough every side draft does this. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted October 9, 2009 Share Posted October 9, 2009 I always balanced by ear and had good success. Hold a length of hose to your ear and hold the other end in the venturi. Make the hiss sound the same in all the carbs by adjusting the screws in the linkage. Set the idle. Set the idle mix. Set the idle again. Repeat a few times. Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted October 9, 2009 Share Posted October 9, 2009 I always balanced by ear and had good success. Hold a length of hose to your ear and hold the other end in the venturi. Make the hiss sound the same in all the carbs by adjusting the screws in the linkage. Set the idle. Set the idle mix. Set the idle again. Repeat a few times. This. My buddy that retuned mine the first time did the entire thing in about 10 minutes, including my 5 minute test drive, and then resetting the idle about 100rpm higher than he had first set it for a smoother idle. Unless you've ever listened at the end of the hose, it might sound hard, but it's *really* easy to tell once you know the sound. Also, make sure all your valve lashes are the same before you start, since that'll mess it up otherwise. Quote Link to comment Share on other sites More sharing options...
RB30X Posted October 9, 2009 Author Share Posted October 9, 2009 Awesome, thankyou. Quote Link to comment Share on other sites More sharing options...
Sam280Z Posted October 9, 2009 Share Posted October 9, 2009 Fuel level is probably too high like wondersparrow said. How fast is your idle speed? If you hear whistling, it may be too high. The idle speed you run depends more on the cam. With a near stock cam, my Mikuni 44PHH carbs will idle at 500 rpm all day long. Quote Link to comment Share on other sites More sharing options...
yetterben Posted October 9, 2009 Share Posted October 9, 2009 All i am gonna do is shake my head gas comes out of all side draft carbs when you plug the inlet. His floats very will could be set to high but you cant base that on when i stick a uni syn on it for 2 seconds gas barfs out. Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 10, 2009 Share Posted October 10, 2009 Ditch the uni-synch and get a real dial indicating synchrometer such as recommended and sold by Weber. It doesn't restrict the flow to lift a piston, it uses an internal fan that rotates to move a dial and give you a reading on airflow. You can leave it in place forever and the idle is not changed one bit. Can't do that with a uni-syn! Idle synch is accomplished with the idle stop screws, and then linkage adjustment takes care of off-idle synchronisation. THEY ARE TWO DIFFERENT THINGS! Gene Berg has a good article on bench-synching carbs for VW's, and since that was the way I was trained, that's the way I started. It really saves time when you start from scratch (like bying a set in a basket and have to assemble everything...) Linkages are disconnected for idle synch. Then off idle synch is checked (hard as hell with a UNi-Synch, but child's play with the Weber Tool). Last check is to disconnect linkages individually while at idle to see if anythign changes. Good Luck, but I think you are just a victim of the uni-synch, especially if you are idling near 1000 rpms and hold it on there a tad to long, with a tad too small opening. Float should be in the lower 1/4 of the scale at first... If you hold it on more than a fraction of a second to get a flash reading on the red floating slider in the column, you WILL affect airflow enough to change the idle and must let the cylinder clear, and idle restablize before checking it again. Unisynchs suck. Quote Link to comment Share on other sites More sharing options...
johnc Posted October 10, 2009 Share Posted October 10, 2009 http://www.duckyimports.com/servlet/Detail?no=5 Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 10, 2009 Share Posted October 10, 2009 That's the animal. I would have called it the 'SK Synchroniser' like on the box I got it in, but I've seen it sold by Weber everywhere but Japan...so figured that was less obscure. Note the scale is KG/H the reading is actually the airflow through the cylinder. Knowing airflow, and injector pulsewidth lets you roughly correlate AFR as a check as well...if you like to do math for idle intellectual exercises... Quote Link to comment Share on other sites More sharing options...
RB30X Posted October 14, 2009 Author Share Posted October 14, 2009 Hmm, can't seem to find one of those over here in Australia. Also, using a Webber tuning reference, it shows an air bypass screw?? My webbers don't seem to have one. Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 14, 2009 Share Posted October 14, 2009 BOLLOCKS! (like the local lingo attempt?) There were at least a Dozen of them in use at the muscle car weekend at Eastern Creek last month. They have to be getting them from somewhere. If all else fails Demon Tweeks out of the UK sells them. Also JC Whitney sells one, not the Weber/SK unit, but very similar (gauge and needle design) --- JC Whitney will ship as well, and the one they sell is probably about half the price that Demon Tweeks wants for the Weber one. I have had the JC Whitney one since 1986, and it hasn't failed me yet. Matter of fact, I stand corrected, I just googled "jc whitney synchrometer" and it pops up with the SK/Weber one for $88 US, and the other one for $55 is the crappy uni-synch. I searched one back from the page with the Weber Synchrometer on it, and up pops my old favorite the Schleyer one that I bought from JCW while I was stationed in Japan in 86---it's a whole $40 US, and I can attest it works just as good as the one costing twice as much, and 1000X better than that overpriced piece of die-cast sh*t sold by Uni-Synch! Weber One: JC Whitney P/N 14219G http://www.jcwhitney.com/jcwhitney/product.jcw?nval=1101021435&statenval=1101021435&productId=2004219&shopid=100001&pageid=12&TID=8014524F&utm_source=Google_Product_Search&utm_medium=CSE&utm_content=product-14219G&zmam=73771597&zmas=18&zmac=129&zmap=14219G Schleyer One: JC Whitney P/N 1JA882792 Schleyer P/N 200+H10+18 http://www.jcwhitney.com/CARBURETOR_SYNCHRONIZER?ID=12;0;1101021435;0;100001;ProductName;52;0;0;0;2008076;0;0 Not all the Webers will have the air bypass equalizing screw. That is a later model response to Dellorto which had them, and allows for compensation of a twisted throttle shaft and butterflies that aren't quite in line after sticking and throttle stomping too much... Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted October 14, 2009 Share Posted October 14, 2009 Before you spend the money, give the "fuel line in the ear" trick a try. Just listen to all the barrels at first and see if you can hear the differences in sound. If you have a halfway decent ear, you can tune them. Quote Link to comment Share on other sites More sharing options...
Lazeum Posted October 14, 2009 Share Posted October 14, 2009 Before you spend the money, give the "fuel line in the ear" trick a try. Just listen to all the barrels at first and see if you can hear the differences in sound. If you have a halfway decent ear, you can tune them. I second that, I threw away the uni-sync to use the hose method. Make sure also to have the hose at the same location for each barrel. If you stick the tip of the hose deeper, the sound will change. I just use my fingers as bumps on air horns to locate hose the same way. Moves are fast since you just have to listen for 2-3 seconds each time, so holding the hose with a consistent way helps. Other people say this method is not good enough, I kind of disagree since my idle is more than acceptable. Quote Link to comment Share on other sites More sharing options...
wax Posted October 14, 2009 Share Posted October 14, 2009 When i was working on alfas with the down draft webers We had a system using water in a tube and used it to balance the carbs It hooked to the bottom of each carb and it would show the vacum each carb was pulling You would need to do it with all 6 cylinders but its the easiest way to balance the carbs Quote Link to comment Share on other sites More sharing options...
wondersparrow Posted October 15, 2009 Share Posted October 15, 2009 http://www.racetep.com/weberX.html#websynch Thats where I got mine. $45 seems like a good deal. Quote Link to comment Share on other sites More sharing options...
jasper Posted November 3, 2009 Share Posted November 3, 2009 Has anyone used the color tune to dial in the fuel mixture first??? Looks and sounds like it works!! Any one with personal experience??? I'm going to order the sk flow meter from Ducky. Quote Link to comment Share on other sites More sharing options...
RB30X Posted November 10, 2009 Author Share Posted November 10, 2009 So I bought one one these carb sync tools and measured each carb. With each throttle set to 0% the resutls were as follows (figures are from the carb sync increments) Cylinder 1 2 3 4 5 6 Throttle 0% 1.0 1.1 1.0 1.8 1.3 1.0 5% 2.0 1.9 2.0 2.8 2.0 1.7 3&4 and 5&6 seem to consistently be different indicating bent shafts and 1&2 were a bit random?? Providing I can still get a low rpm idle, does this much difference really matter with low rpm air flow. I'm guessing the shaft itself would only be a bee's dick out anyway so at cruising or high rpm the difference would be minimal. I will perform some more measurements at higher rpm increments to get more readings from the higher end of the scale of the carb sync tool and see how different they are. Quote Link to comment Share on other sites More sharing options...
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