Fuel and Air Screws - how to find the proper settings?

With the car in gear you have 800, what happens when you turn the air screw on the side of the carburetor to get it to go down to 650? Are you sure the float level is adjusted correctly?
 
When I try and turn the air screw down at 800 RPMs in gear, the car just dies. And it just does not sputter and grasp for air . . just dies. I rechecked all the vacuums and all hooked up and getting good pull. No open ports on the Carb. Its runs and runs as expected when everything is set at 1000 RPMs in park and 800 RPMs in gear. . . but we know that is not right. I will continue to look and maybe find some old school mechanic around here. I will probably need to pull the Carb and check the float levels. I did look into the carb yesterday and I am getting a good squirt of gas when pulling on the accelerator line. Thanks . . . JIMB
 
I really think you have to reopen the carburetor and check the float level and check the idle passages that feeds gas below the closed throttle plate. Maybe you know this already but those passages feed gas at idle and as you open the throttle typcially there is a idle transfer slot which as the name idicates starts to richen the mixture as the throttle goes past idle and before there is sufficient airflow throught the venturis to cause them to feed gas.
 
When I rebuilt my carb I soaked everything overnight in a gallon container of Napa carb cleaner. Then I cleaned everything with spray carb cleaner and blew out all the passages with compressed air.
______________________________
 
I talked with a local old school mechanic. He said one of the issues I have is the new spark plugs I put in are not matched for the new HEI Distributor. When I installed the new plugs I was on the points/condenser system. But I have since moved to an HEI system. He said I have to get the right spark plugs and gapes matched to the HEI and car. I have read threads on HEI and most threads say gap your plugs between .035 and .0400. I have mine gapped at .035 so I am thinking I should be ok and the issues I am having are NOT from improperly gapped plugs. Thoughts????
 
Last edited:
The plugs can be opened up to .045 but they are not the source of your problem. I have my system upgraded to a pointless system with an aftermarket ignition box and run the original type of plug opened from .035 to .045. I still think your carburetor has a float or blockage issue. Where did you buy the rebuilt kit? What spark plug are you using manufacturer and part#? I found this video on a rebuild, maybe it will point out something you missed.

http://www.youtube.com/watch?v=6RTf2yrGcA4
 
I bought from Mike's carb . . and actually followed all his videos on how to rebuild. I guess I will go ahead and pull the thing off and check it . . oh well. More to come. Thanks . . . JIMB
 
I was/am still not buying the issue was/is with the carb. Couple reasons. When I put the car in gear the car just dies . .no gurgling . . no choking . . it just dies. And I was getting erratic RPMs when in idle. I am fairly confident I built the carb correctly. So I turn to the electronic portion of the car. Back to a thread several months ago where MELSG5 asked/told me I should not (could not) use the old points/condenser voltage wires with for my new HEI system. After reading several threads and re-reading MELSG5 post I am thinking here is the answer. The voltage that is getting to my MSD when the car is running is NOT actually12V because I am using the old wire from the points/condenser system. I believe this wire carries less than 12V while the car is running. I am going to rewire the voltage getting to my MSD and make sure there is a true 12V all the time. Thoughts and theories??? But, why when I have the IDLE set at 1000 RPMs in Park the car kinda holds a 800 RPM idle in gear?????
______________________________
 
Try giving it a little more timing. You said your at 10 deg. Go as high as 16 deg and see how the motor likes it. You may hear an immediate difference. Can't hurt to try.
 
Problem solved!!!! The original wires that were going to the ignition coil only carry from 6.09 - 6.60 volts during car idle. Right before start up the wire shows 12V. But only the 6ish volts during idle. I should have listened to MELSG5, in another thread, and found a true 12V source for the HEI. I could not check the volts under load as I have no one to help me this morning. But I am going to guess as the car goes under load (Drive or Reverse) the volts drop. I temporarily hooked the HEI up to the battery and all is good. Smooth idle at 800 RPM in Park. Very little variation in RPMs / Less that 15 RPMs variation. And I believe that variation in RPMs is coming from the alternator recharging the battery. Before I was getting a variation of up to 60 RPMs - which I am guessing was really the resistance going up and down from 6.09 - 6.60 in the old wire. When I put the car in gear it holds a nice RPM idle around the 620 RPMs. I will continue to manage the fuel and air screws and see where I can get it. First I need to find a constant 12V source connected to ignition. But I feel much better about what is going on. Thanks to all for the help and hanging in there with me. Greatly appreciated. Thanks . . . JIMB:D
 
I had completely forgotten about the other post concerning voltage to your HEI. Check power going to the wiper circuit both during cranking and while running as a possible source for constant 12V. Glad you found the problem.
 
I am testing some wires to tap into for my 12V. There is one of the original wires going to the original ignition coil that does cary 12V before starting and during running. The other wire there was the resistor wire cause it ranges from a negative range to a positive range. Anyway, the one wire carrying 12V carries like 300ish Volts during the starting cycle. Whats this about? The car does not start using this wire. I was also going to use the wire going to my Idle solenoid - I am not using the solenoid. I tested wire before starting and during running conditions and it carries 12V. But again, when starting in carries 300ish Volts. The car did not start using this wire. I don't understand where these 300ish volts are coming from and why they are being pushed during the starting cycle.
______________________________
 
Unless you made a typo there is no way the wire can have 300 volts. Do you have another volt meter to check with? The solenoid wire would make a good source but in one sentence you say you got 12 volts and than you say you got the 300 something readings?

"I tested wire before starting and during running conditions and it carries 12V. But again, when starting in carries 300ish Volts."
 
Here is what I have. I have the car connected to the battery but I do not have any volts going to the HEI. When I turned the key to Ignition-1 I tested the wire (choke solenoid) and found 14 volts. When I turned the key to Ignition-2 I tested the wire and found 14 volts. Then I tried to start the car (but its not going to start because I have no volts going to the HEI) and found the 300ish volts on the wire. Then I put volts to the HEI from the battery and tested the wire and found 14 V.
 
I'm not clear what you mean by turning the key to Ignition-1 and Ignition-2 versus trying to start the car? Is Ignition-1 the accessory position and Ignition-2 the run position? In addition how can you get 14 volts with the engine turned off? That is too high a reading for a normal fully charged battery on a turned off vehicle. Read this link and see if you missed a step in hooking up the HEI. I'm wondering if you are getting some sort of voltage feedback with the original wires disconnected. I guess you are using a digital gauge?

http://www.pontiacstreetperformance.com/psp/HEIconversion.html
 
Since you have not disconnected the wire from the R terminal on the solenoid, when you crank you get battery voltage going up the wire to the connector that was previously connected to the ignition coil and it feeds back down the resistor wire, the wrong way, to the ignition switch. Results unpredictable any may cause your problem.
______________________________
 
I had already separated the two wires going to the old ignition solenoid. They are both capped off and separated from each other. I am using a digital gauge. If I turn the key to the right one spot I believe this is referred to as Ignition-1 position. When you turn the key further right and try to start the car this is called Ignition-2. When the car starts the key turns back to Ignition-1. I see where I created the confusion. I will have a buddy come over and double check what I am seeing and getting. More to come . . . JIMB
 
Ok. The 300ish Volts I was reading was actually . . MiliVolts . . I did not see the legend switch on me. Oh well. I believe I can use one of the old wires as it does keep 12V all the time while in Ignition 1 position (when the wire is all by itself.) I have to replace the wire that is used in the Ignition 2 (starting and the resistor wire) position. I have to find where the resistor is in the wire. I can trace it a little but I do not want to undo my dash just to find the resistor. My option is to just cut that wire right behind the ignition switch and run a new wire from the cut wire right to the HEI distributor. That will give me 12V in Ignition 1 and Ignition 2 positions. More to come. Thanks . . . JIMB
 
I cut the ignition 2 wire under the dash right before it went into the wire block and tested for voltage when trying to start the car - still 9.4 volts. So the resistor is either up in the wiring harness in the dash or in the ignition itself. I will try and pull the wire through tomorrow morning and see what I get. More to come tomorrow:cool:
 
You must log in or register to reply here.

Share this page

Back
Top