Don Jordan Posted December 20, 2009 Report Share Posted December 20, 2009 I just rebuilt my carburetors and got them back on. (more on that later) I asked my friend to come over and help me adjust them. Everything was back together and I fired the car up. It ran a little uneven but it was running. I was a little concerned that if you put your hand over one carb there was a slight decrease in idle but if you put your hand over the other carb it would stall the car out. I have one of those vacuum gauges that you put on the carb to see how it's sucking. The first one was perfect the second one sucked the little red ball to the top. It idles fine but the two carbs aren't in sync. Now for the stupid part. After a while I was beginning to get a head ache. We were running the car in the garage. What could I have been thinking. I rolled it outside to continue. It's only 59° outside - I was concentrating so much on the carbs I wasn't paying attention to the environment. I'm sure there must be a rule about running the car in the garage. I guess I forgot. Why would one carb be doing all the work. I screwed the air fuel screw in all the way and it made no difference. I just rebuilt the carbs what could I have done wrong? Carters B&B. Quote Link to comment Share on other sites More sharing options...
dezeldoc Posted December 21, 2009 Report Share Posted December 21, 2009 Don, back both idle screws off so the throttle plates are all the way closed. Turn both mixture screws in till they bottom out and back each one out 1 1/2 turns, then start it, you will need to keep it running, adjust one idle screw in till you just here the idle come up, adjust the other up till it just increases. now put the sync gauge on and adjust the idle to 750 or what ever you like it at on both carbs, the gauge should read pretty much the same. now you can finish the air/fuel mixture screws. Quote Link to comment Share on other sites More sharing options...
Tom Skinner Posted December 21, 2009 Report Share Posted December 21, 2009 Don, I rebuilt 2 carburetors in the last month and found that if the Idle Mixture Screw Tip is not Conical but worn or distorted (pointyish) or bent you will never achieve a smooth Idle. Look at some on this Site: http//old-carburetors.com/chrysler htm Otherwise I think the advise you just got on the prior thread is the best route. Tom Quote Link to comment Share on other sites More sharing options...
greg g Posted December 21, 2009 Report Share Posted December 21, 2009 The syncrhronize tool is for linking up the throttle plates so they work together. First step is to assure they are both closed at idle or all the adjustments you can do will not make any difference. If one throttle is slightly opened it will negate the idle itsc ircuit and the other one. Remember the idle jet is set and the screw adjusts the amount of air mixing with it. Once the throttle plates begin to open the idle circuits are out of the loop. You may need to make some adjustments of your main linkage to the carbs to assure the throttle plated are both closed all the way. Quote Link to comment Share on other sites More sharing options...
claybill Posted December 21, 2009 Report Share Posted December 21, 2009 been there...could have sworn that there was something amiss in the motor....nope..i just fiddled withthe air screw and the throttle 'flap' (plate) and linkage and finally got it to work pretty even.... it ran fine although it was pulling 80%% from one carb. now they seem more even. actually that eveness is mostly on idle....once you get the throttle open both carbs pull about the same.... bill Quote Link to comment Share on other sites More sharing options...
dezeldoc Posted December 21, 2009 Report Share Posted December 21, 2009 Greg, it is also for the air fuel mixture. Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted December 21, 2009 Report Share Posted December 21, 2009 This is the tool Greg and I used to adjust the throttle plate linkage on both carburetors. It has no effect on adjusting the air/fuel mixture. Once the throttle plates are in sync then adjust the air/fuel mixture for a smooth idle. Quote Link to comment Share on other sites More sharing options...
greg g Posted December 21, 2009 Report Share Posted December 21, 2009 Since the carbs are non adjustable analog devices, please explain how the fuel air mixture is adjustable with a sych tool. Other than the amount of air flowing through them,which is decided by displacement and throttle plate opening, the only way to effect an actual ratio change would be larger or smaller jets in conjunc tion with a given flow. Which would entail dissasembly of the carb and physically changing the jets. The only external adjustment is the idle air screw, and it only effects the throttle closed idle mix. Quote Link to comment Share on other sites More sharing options...
dezeldoc Posted December 21, 2009 Report Share Posted December 21, 2009 Works with mine, if not use a vacuum gauge and adjust till you get the highest reading. Quote Link to comment Share on other sites More sharing options...
kencombs Posted December 21, 2009 Report Share Posted December 21, 2009 Greg, The air fuel mix at speeds above idle is in fact fixed, either through a power enrichment circuit of some kind, (vacuum piston, needle, diaphragm, poppet valve etc) or main jets. But at idle, the amount of fuel is regulated by the idle jet adj screw, the air by the idle speed screw. So a change in mixture using the idle jet screw will change the idle speed also, resulting in a change in airflow, necessitating, a readjustment of the speed screw. Quote Link to comment Share on other sites More sharing options...
Don Jordan Posted December 21, 2009 Author Report Share Posted December 21, 2009 Thank you all - now I am totally confused. I'm going to print out all these posts and take them outside with me and see what happens. I need to make sure everything is tightened and there are no leaks. Then I will be back to find out how to change the vacuum. One carb is pulling way more according to the sync tool. But I gotta tell you - when it runs it sounds great. thanks again d- Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted December 21, 2009 Report Share Posted December 21, 2009 It has been my experiance that the air flow tool I pictured above works only to adjust the carburetor linkage to insure all throttle butterflies are opening and closing at the same time. Adjusting the air/fuel metering screw will affect engines idle rpm's but it will not correct an out of balance air flow between two or more carburetors. Quote Link to comment Share on other sites More sharing options...
Don Jordan Posted December 22, 2009 Author Report Share Posted December 22, 2009 Thank you all. I've actually printed up all the responses and I'm taking them into the garage. Since the really unknown factor here is I just rebuilt the carbs I may have to go back to square one. In the rebuilding kit they offered 4 gaskets for (I don't know the name) but it's the riser above the base. Since I only took one gasket off I only put one back on. But on the other one I put 2 extra gaskets. Would that be enough rise to change the vacuum? It's the only thing I can think of that was different. I did put a new air/fuel needle valve that Norm gave me but that shouldn't have any effect. Anyway - here I go. Quote Link to comment Share on other sites More sharing options...
Young Ed Posted December 22, 2009 Report Share Posted December 22, 2009 Don there are two slightly differnet styles to those gaskets. You should only have the base then a gasket then the spacer then a gasket and then the carb body. The 2 extra gaskets are just that-extra. I can't say how that would effect your idle though. Quote Link to comment Share on other sites More sharing options...
greg g Posted December 22, 2009 Report Share Posted December 22, 2009 It won't effect the amount of vacuum generated however they do play a factor in how the vacuum is used. the carburetor power valves, the circuit that takes over after the shot from the acc pump, relys on a vacuum signal to operate. This signal is routed through a slot cut inthe gasket that matches to a port int he bottom of the carb. If these are not aligned, the power jet will be opened all the time as the vacuum serves to pull down on the spring that pulls a needle out of the jet. If that vacuum is missing, the spring will hold the needle open causing the carb/s to run rich. Whats the difference. Bob Van Buskirk has the wrong gasket on his 54 plymouth, and he complained about poor gas milage, this ona single carbed engine equiped with a OD. in OD on the highway he was barely getting 14 MPG. With the gasket lined up correctly, he gained nearly 5 MPG. The upper one in the pic has 4 slots so it nearly impossible to misalign it, However, not all gaskets are created equal. So locate the small hole in the bottom of your carb and assure it lines up withthe slot int he gasket. No slot??? cut one!! Quote Link to comment Share on other sites More sharing options...
Normspeed Posted December 23, 2009 Report Share Posted December 23, 2009 (edited) I if you put your hand over one carb there was a slight decrease in idle but if you put your hand over the other carb it would stall the car out. It idles fine but the two carbs aren't in sync. Why would one carb be doing all the work. I screwed the air fuel screw in all the way and it made no difference. I just rebuilt the carbs what could I have done wrong? Carters B&B. Don, to get to your original question, with twin carbs you need to do two things. One is to make sure both the throttle plates are operating in synch. Then, you need to adjust the idle mixture screws for both carbs. I think from your description the throttle plates are way off, and those require loosening the twin carb linkage, then adjusting the throttle plates (with the idle speed screws) then tightening the connecting linkage so both of them close and open in synch. I'm attaching a really useful little set of instructions posted some time back by another member. I've used this method and it works great. It's at the lower right of the page under "Recommended procedure for setting idle" You follow that procedure with the connecting linkage between the two carbs loosened, then after the adjustment procedure tighten the linkage that connects them. Once you have them close by this method your synch tool might prove more useful for fine tuning the carb balance. Don, if you need a larger copy of this let me know and I'll either post it up on Photobucket or email to you. Edited December 23, 2009 by Normspeed Quote Link to comment Share on other sites More sharing options...
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