I guys.

Today I change jets on my Carter AFB 625 CFM to lean it because was running too rich. Now i have the problem that the car is idling to high, 2200 RPM according to tachometer, the idle screw is all out and continues idling at 2200 RPM, the unique way to low the RPM is totally closing the idle mixture screws.

I think that could be a vacuum leak because if I put my hand over the air horn the RPM increases but I want to have other opinions to solve the problem

 

if the AFB is made for the engine it is on, it WILL not be to rich. unless something is wrong. sounds like you have trouble with the floats and a vacuum leek. vacuum leak could be gaskets. may be the carb needs to be overhauled.

 

I bought the carburetor some months ago as an used item on ebay, I rebuilt it and was working fine, a bit rich but working great with idle at 600 ~ 650 RPM

Maybe I break a gasket today while changing jets.

Question: Is possible to have a vacuum leak inside the brakes booster? My car booster always had make a strange noise like an air leak when I brake, I don't know if this can affect the carburetor work.

 

What Model Carter ? 9636 ???? Should just bolt on and go !!!!

 

on the jets. they do NOT need to real tight, just sung works. Title: AFB and edelbrock carb / the short verson.

setting an AFB carb takes time. make only small changes. and give it time, dont make changes in an hour or two. drive it in different ways over a day or two. on AFBs or AVSs change only the jet OR rod at one time. and start with the jets. a .003" change can be felt if you try. dont forget .003" on a .060" jet is less change than .003" on a.100" jet. Then start changing the rod. A little is a LOT. i do have a computer program to cal any combo of changes. but it is lost in some main frame of my sons. Sometimes you can set the float level to 5/16”. the stock setting is 7/32. if at 5/16” at idle the fuel runs out of the main discharge nozzle reset to the stock setting. NOTE: do NOT change jets AND rods at the same time. Do not put the jets in tight, just snug is fine. allso i have computer program that will calculate correctly any combo of change. check this site out. its my sons i think it still works. *http://clarkehackworth.com/files/JetsAndRods.html

 

In theory, the jets should not affect the idle, because the idle is controlled by a different circuit. I am interested in your challenges, because I am about to reject my Ederblock 750 AFB, which I suspect is running a bit lean at WOT. I am planning on changing only the jets for the secondaries.


You can easily check if the booster is causing vacuum leaks by disconnecting the hose and plugging it, and see if it has an effect in idle.

 

iam sorry i did not mean to say the main jet controls the idle. on chrysler O.E.M. AVS carbs have a lean idle circuit. the Ederblock 750 AFB may have the same thing. it is easy to fix just drill the idle jet by .001-.002". on the idle jet a little is a LOT. if you go to big just solder it and redrill. i use a drill index set #61-#80. and a pin vice.

 

When I solve this issue I'm going to try to disconnect the booster to see what happens. If the booster has a leak, which could be the way to fix it? or the best way is to replace it?


Would be nice to know what was the stock jet size for a 9636s back in the days. Could be a good point to start making all the tuning

Yes is a 9636S 625 CFM AFB, the carb was working fine but I know it was running rich because the exhaust smells a lot of gas and the car has poor mpg, 9 to 10mpg on town with a 360 SB and the spark plugs are black

I don't think this could be the problem because the car was idling fine, the problem just start after the jet change

 

The booster can cause a vacuum leak. When you brake, does the engine begin to shake, and if done at idle, do the rpm's increase?

 

did you put a square bore carb on a spread bore manifold? with out the spcel plate and gasket from edelbrock? somewhere i have the charts for that carb. but am in the middle of moving now and cant find any thing. with that carb if it is on a engine that is close the engine it came on the jetting will be very close to what you need. on very old Carter charts sometimes they will have some differences to newer chart. the edlbrock carbs tend to have rods the have to much of a step from the cruse step to the power step. all that iam talking about applys to stock or close to stock mopars. not to all out race emgines.

 

No, I put the Carter 9636S on a Square Bore intake so I shouldn't have problems at this part.


Another question: Is possible to have vacuum leaks between the intake and the cylinder head?

Yes, when I brake I can feel a change on the engine rpm and sometimes shakes a bit. I think I've a vacuum leak in the booster

 

i had a booster that would be ok then leek, sometimes when hitting the brake. try blocking off the booster. should get an answer then.

 

The problem was the throttle linkage so I bought an Edelbrock 1481 and problem solved but right now I've another problem, I don't have idea how must I install the kickdown linkage. Here are some pics attached