tri power weber question

64falconsix

64falconsix

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Supporter 2022
Supporter 2018
I installed an edelbrock AFR to help with the tuning but i am still having problems. current jetting is 170 main in the center and 155 mains in the ends and 65 idle jets. the best i can manage with jet changes are cruise afr of about 13.0 , Idle jumps around bettween 13.0 to 14.5 . during light accelaration about 13.5 if i step into the center carb a little or open the ends (WOT) the AFR goes off the scale on the lean side. during WOT i can slowly back off of the throttle and at a certain point the meter starts to read again but on the lean side until i come back to a cruise. the plugs show a light grey to dark grey on the insulator and strap with a light sooty black on the base and although i see no black smoke during idel it smells rich. any suggestions would be apprieciated.
 
followed the weber instructions on setting the idle circut , the instructions say to set idle speed screws to 1 1/2 turns out from contact on both speed and mixture screws for the initial setting . no matter what idle jets or mixture setting i try it idles very low the stalls 400 or 300 rpm (with the speed screws set at 1 1/2 turns), for the 15 or 20 seconds it runs at that rpm adjusting the mixture screws does'nt make any changes. the instructions say that anymore than 2 turns out on the idle speed screws cause the carbs to run on the transition circut and will cause a rich idle.I can get it to idle but only on about 3 1/2 to 4 turns on each idle speed screw.IICRC idle vac was around 14 or 15 inches.
 
I had a hard time to get mine to idle right until I noticed that the throttle plates had rough edges that prevented them from closing all the way. In order to get a decent idle you had to crank open the jets but then the idle was way too high. I removed the plates and used some 1500 paper to smooth out the edges so they would close all the way. I didn’t have any problems after that and the idle adjustment was about 1 ½ turns out.

Gene
 
8) the idle mixture screws do nothing above 1500 rpm. you have a problem going lean at high speed, and that indicates an air corrector jet that is too large, thus allowing too much air to mix with the fuel emulsion.
 
thanks for the repleys, I went down a few sizes on the air corrector jet and eliminated the wot lean issue I think maybe 1 size bigger will get me where i want to be . the AFR reads steady now where it was a little irradic before , its just a little rich throughout the range. i connected the vac. gauge to manifold vacuum and can only manage between 9 to 12 inches of vac. at 600 rpm it seem to slowley fluctuate with the rpm. which randomly sounds like it wants to stall. even running the rpm to 1000 still about 11 0r 12 inches. the idle mixture screws do cause a noticeable change in smoothness when adjusted (too much causes it to stall) and account for a vac change of 2 or three inches. It is still running rich at idle and the idle jet change doesnt seem to make much of a difference. does the vac sound right or should i look for a vacuum leak.also i still have to turn the idle speed screws in about 4 to 5 turns from contact on all 3 carbs to get a 600 rpm idle.
 
8) the idle system should also have an air corrector jet on it. perhaps go up two sizes on that and that should put you close.
 
can't seem to find out what the problem is, still running very rich at idle. I changed idle jets mutiple times with several different sizes. and adjusted the idle mixture screws with a vacuum gauge. I checked the schematic and the idle circut does'nt show an air jet just the idle jet. I pulled the plugs before changing the jets ( after driving) and they were light grey, after idleing while trying to tune 15 or 20 minutes total run time the plugs were sooty black. I checked for vac leaks,leaking needle seats, fuel pressure, valve adjustment, and timing and everything looks good. I even looked down the carb throats while running and did'nt see any excess fuel pouring in . also these carbs are new and have ran rich at idle since i put them on.
 
if I am reading this correctly, you are trying to use all three carbs at idle? Idle circuits should be disconnected electrically on the outer two carbs and the idle mixture screws should be run in all the way on the outer two as well. Middle carb is your idle and cruise carb until you bring in the outers at half throttle or so.
 
yes I have been trying to use the ends to idle also. I found a post last night about useing the center for the idle and cruise and tried that tonight , running the mixture screws all the way in on the ends, it still ran rich. so i took the end carbs off and blocked the ends of the manifold to run on the center carb and there was no change.I will look at the float level tomorrow. I have not heard of disconnecting the idle circuts electricley, could you explain the procedure or what is needed to disconnect the idle circuts.
 
On the side of the carb where te idle jet is housed, there is an electric solenoid inside that housing. When connected to 12v, it opens up the idle passage and shuts it off immediately when the engine is shut down so no fuel continues to flow and cause run-on. Only the center carb should have this circuit wired. Also, the outer carbs idle screws should be backed out all the way so the main jets aren't dumping any fuel at idle and causing a rich condition as well.
 
I don't have the solenoids on my carbs, i also had a few thoughts about the main jets adding to the mixture at idle . one post says idle mixture all the way in and the other says all the way out???. I tried running on one carb still rich. there is something about the carbs that i am missing. did you also back off of the end carb idle speed screws all the way also.

211001.jpg
 
Outer carbs mixture screws turned all the way in-don't force them, just snug them. The idle speed screws should be turned all the way out so that the butterfly is shut fully at idle, otherwise, the mains will begin to dump fuel when they shouldn't be. I actually had to stiffen up the return springs on the outers as just cruising, the vacuum would begin to pull the butterflies open sometimes!
 
thanks for the info john. I had the same problem with the ends opening , i found some springs that fit inside the stockers on the carbs. the double springs solved that problem.last night I reset the jetting and readjusted the carbs , also checked the float levels. i'm still running a little rich. plugs look good a cruise but turn black if i idle for very long, no black smoke just the smell of unburned fuel and a slightly rough idle. have you had this issue with your setup.
 
You were on the right track.
Simplify your setup by removing the end carbs and blocking the manifold holes.
If you can't get it to run correctly with this setup it will never run right with two more carbs added in.
Try adjusting the center carb mixture screw all the way in. If the car does not die then the carb is supplying gas through another path. Find it and fix it.
When the single carb setup is running good then add the other carbs back in.

In the seventies I had a 61 chevy six 235 ci. I put a tri power on it. The linkage supplied with it had a slot in it for the middle carb that made the middle carb open by about 10-15 degrees before the end carbs were engaged. I had very few problems getting this to run right just bought two rebuilt standard carbs for the car slapped it all on, adjusted the idle mixture screws all the way in and idle speed screws all the way out on the end carbs, and was good to go.
 
Forgot to ask if you have a pressure regulator installed-these carbs don't like anything more than 3 lbs put into them or they will start dumping fuel. I used the Summit one and it works fine. Mine still runs a little rich at idle, but I need a new needle and seat for the main carb-just haven't had the time :D
 
I do have a pressure regulator in this system its a mr gasket set at 3psi I also installed a pressure guage to keep a eye on the pressure. I seem to have it tuned a little better on the bottom end just a little lean at the top now.
 
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