stav2201 Posted February 11, 2014 Share Posted February 11, 2014 I recently bought a 1975 280z with triple webers and a cannon intake, My jet setup- 40mm carbs (x3) Air correction jet- 170 Emulsion chamber- F11 Main jet- 125 (Not sure what size chokes) I have the Fuel Psi set at 2 1/2 Im running Stock 280z coil with the stock ballistor. My timing is set at 12 Dbtdc i also have a wide band O2 set up and installed for tuning with a timing light as well. I have a general knowledge of how to tune these but its become a little more difficult than i thought, Are there any members with a good amount of knowledge on tuning these that would like to help me out this week? Im free tues ,wed, fri before 3:00 Pm, thurs and sat open all day. I would really appreciate any help because i need to get this car running. Quote Link to comment Share on other sites More sharing options...
T-Bone028 Posted February 17, 2014 Share Posted February 17, 2014 (edited) Well is it running? If so, what are you experiencing? Do the basics...check and set the floats to the proper measurements before trying to tune. Verify your main Venturi size...that's your starting point for all initial jetting (my guess based on your main jet size is that you have either a 30mm or 32mm main Venturi, but only one way to find out). Check your throttle plate position relative to the first progression hole, verify how many turns from fully seated your idle jet screws are turned, actually there is a lot of stuff I would do/check/ask...but, I think the redline/weber/top end performance website has a good "getting started guide". I can try to help... Edited February 17, 2014 by T-Bone028 Quote Link to comment Share on other sites More sharing options...
stav2201 Posted February 21, 2014 Author Share Posted February 21, 2014 Well is it running? If so, what are you experiencing? Do the basics...check and set the floats to the proper measurements before trying to tune. Verify your main Venturi size...that's your starting point for all initial jetting (my guess based on your main jet size is that you have either a 30mm or 32mm main Venturi, but only one way to find out). Check your throttle plate position relative to the first progression hole, verify how many turns from fully seated your idle jet screws are turned, actually there is a lot of stuff I would do/check/ask...but, I think the redline/weber/top end performance website has a good "getting started guide". I can try to help... I had it running decent for a little but then realized all my valves were horribly out of spec. Now that they are within spec (8 on intake 10 on exhaust) the car dies as soon as i put any load under the engine, it idles perfectly and i had them set very nicely at idle. When i put it in reverse to take it for a spin it dies as soon as i let out the clutch. I feel as if it is a fuel delivery issue, maybe my floats are out of spec or my accelerator pump may be wrong, (I believe it said 40 on it). Quote Link to comment Share on other sites More sharing options...
stav2201 Posted February 21, 2014 Author Share Posted February 21, 2014 (edited) Ok i took apart one carb and here are the spec This is on a L28 block with an N42 head + stock cam Triple weber setup 40 dcoe 18 Chokes- 27mm Main Jet assembly: Air correction- 170 Emulsion tube- F11 Main Jet- 125 Idle jet- 45 f9 Pump jet- 40 Float- 225 I want to measure my floats but i dont know what the standard spec for a 280z should be, online it says 12mm? Since my car is also dying under load, Im wondering if my pump jet is to small, or if it just my floats being out of spec. Edited February 21, 2014 by stav2201 Quote Link to comment Share on other sites More sharing options...
T-Bone028 Posted February 21, 2014 Share Posted February 21, 2014 Accelerator pump jet isn't going to cause that. When in neutral and you rev, does it die? What does your AF gauge read? Do all throttle plates operate nicely? Binding in your linkage? What's your full jetting? Where is your throttle plate in relation to the first progression hole? Before doing any trouble shooting you should really check and set your floats. Here's what you need to find out: Carb model (ex: 40 dcoe 18) Main Venturi Aux Venturi Idle jet Main jet Air corrector Emulsion tube Pump jet Exhaust/bleed-back jet And AFTER setting floats to spec, set throttle plates to all 3 carbs to just before the first progression hole, then measure how many turns from fully seated your idle jet screws are ( early carbs are usually between 1-1.5 turns, later I think is 2.5-3), ensure no binding of the linkage, and THEN measure airflow bringing the highest flowing barrel to the lowest. Use best lean idle method for adjusting idle screw. Keep Measuring w sychrometer and monitor AF ratio. Obviously, this is a challenge to tune over the Internet and I could be speaking out my butt. Quote Link to comment Share on other sites More sharing options...
T-Bone028 Posted February 21, 2014 Share Posted February 21, 2014 Sorry, wrote my response without refreshing the page on my iPhone. 27mm main Venturi is pretty small...I would guess 30-32 would be a better size. I have spare 30's if you want to buy them. 2.25 sounds like your needle valve, not float setting. Buy 3 rebuild kits from piercemanifolds with needle valves. I believe 18's come with 1.75's normally. Float setting is actually 2 measurements. Full drop and right before depressing the needle valve to get more fuel. There is a tutorial on how to properly measure and adjust floats on YouTube. After doing that, you can measure the fuel level in the well with the main jet assembly removed. Research Keith Franck method. Floats MUST be properly set before attempting any additional tuning. Quote Link to comment Share on other sites More sharing options...
stav2201 Posted February 21, 2014 Author Share Posted February 21, 2014 My Wideband isnt working right now, it idles and revs very nicely when i had the carbs synced (it was at 950 rpms to 1000) As soon as a put the car in reverse it would lurch, clunk out and die. The guy who sold me the jet setup said that he was running it on a L24, so i would assume that this setup should work decently. I think it maybe be a fuel issue like i said but i will be sure to check the throttle plates. Quote Link to comment Share on other sites More sharing options...
T-Bone028 Posted February 21, 2014 Share Posted February 21, 2014 Standard float settings for 40 dcoe 18's is 8.5 mm from the carb top (before dpressing the needle valve, as measured with gasket in place) and 15mm at full drop. I made a small L shaped "ruler" out of heavy cardboard stock. 8.5mm on one end, 15mm on the other. Just be mindful of the seam in the float. Measurement should be taken without the seam. If you search for the YouTube video, it will explain the process better. 1 Quote Link to comment Share on other sites More sharing options...
T-Bone028 Posted February 21, 2014 Share Posted February 21, 2014 Also, be careful when removing the pin that holds the float in place. The float pin arms can be rather delicate...I broke one of mine!!! Quote Link to comment Share on other sites More sharing options...
stav2201 Posted February 22, 2014 Author Share Posted February 22, 2014 Also, be careful when removing the pin that holds the float in place. The float pin arms can be rather delicate...I broke one of mine!!! I did look at the jet the controls the fuel flow with the floats, it was sticking when i was moving the float. It would get stuck open when the floats fall all the way down and then go back up. Maybe this is my issue, i could be flooding my carbs with this jet stuck open. Quote Link to comment Share on other sites More sharing options...
T-Bone028 Posted February 22, 2014 Share Posted February 22, 2014 Get the rebuild kits with needle valves included. I think they're like $30/each. 175 needle valve is the standard size for 40 dcoe 18's. or you can try to clean the needle valve with carb cleaner...I say replace it though. Quote Link to comment Share on other sites More sharing options...
stav2201 Posted February 26, 2014 Author Share Posted February 26, 2014 I got the car running now and my air fuel ratio is as best as i can get it with my knowledge of carbs and reading the wide band. Im just running into a timing issue since my powerband is absolute garbage. the car has Zero pull after 2500rpms and im afraid of detonation issues since my timing advances to the upper 30's underload or at high rpms. I am running the stock 280z distributor with vacuum advance plugged off. i did read a that you need to switch the distributor to mechanical by welding a bead in the distributor to stop it from advancing itself. i also tried retarding it 6 degrees but it just runs horrible and it nearly bogs out when trying to get out of neutral, but, i did notice a power increase. Ive been trying to find an in depth example on where to weld this bead in your distributor but everything is so vague, anyone have any advice on this or maybe an alternative that isnt mega jolt or some time of computer controlled spark. Quote Link to comment Share on other sites More sharing options...
stav2201 Posted February 26, 2014 Author Share Posted February 26, 2014 i also just did a leak down test and my block is in Excellent condition, all cylinders had between 3-5% leakage Quote Link to comment Share on other sites More sharing options...
T-Bone028 Posted February 27, 2014 Share Posted February 27, 2014 I think stock distributor should only have like 17-18 degrees of mechanical advance, so like 14 degrees initial ends up with 32 total...have a buddy help with a timing light and measure/set full advance to where you want it, and let initial fall where ever it does. I run 32 degrees all in with vacuum plugged (I didn't permanently disable vacuum advance with the bead thing). I will likely buy the new dizzy from 123ignition. Check the threads on here and on classiczcars...seems like a pretty easy way to get full timing control. p.s. you should write up your carb trouble shooting and post it! Someone might be in the same boat as you and looking for help too! Just saying. Sounds like you're going in the right direction. Quote Link to comment Share on other sites More sharing options...
stav2201 Posted February 28, 2014 Author Share Posted February 28, 2014 it turns out my cam was not matched up to my crank, it was off by one tooth which explains why my timing was about 30 degrees advanced! My brother and i fixed the issue and now the engine is running much nicer, its quite, throttle response needs so work but he ran over my syncrometer and now i have to get a new one. Ill post back in here once i get it all set up nice. Quote Link to comment Share on other sites More sharing options...
duragg Posted February 28, 2014 Share Posted February 28, 2014 The master thread for all things Weber is generally considered to be this one: http://forums.hybridz.org/topic/28318-weber-jetsall-who-live-for-their-triples-please-read-this/?hl=webers There is also a Weber Yahoo group that is somewhat helpful. But reading the thread above about 10 times will really bring you up to speed. Quote Link to comment Share on other sites More sharing options...
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