Fuel System: Engine stalling during hard braking

[okc63avanti]

My fresh resto/mod R2+ with Edelbrock 1406 carb will stall under hard braking. The carb doesn't seem to be able to hold idle when decelerating quickly. The original Carter AFB had an vacuum operated idle compensator (dashpot) installed near left front of the carb linkage. The modern 1406 doesn't have one. Edelbrock does sale an electric idle compensator but its stated use is for cars under idle when the AC compressor is on.

Studebaker International sales an idle dashpot (Studebaker part #1558169). Has anyone used this dashpot with an Edelbrock. Does it install without and modifications? I would appreciate anyone who has done this to please provide comments and if needed pictures of your setup.

Thanks, John

[(S)]

Do you still have your old carb? I'd have to check but I think the bracket for the dashpot uses one of the carb studs, should be an easy bolt on.

[PackardV8]

Does it idle OK otherwise? Does your R2 have AC added? Is it an automatic transmission? If so, will it idle in Drive with the AC compressor engaged?

Bottom line, the electric solenoid just increases the idle throttle opening to compensate for the load of the AC compressor engaged. If you don't have AC, it won't do anything for your stalling under decel that you couldn't do with the idle speed screw.

Have you checked the float settings? Stalling on decel is often a problem with floats set too high.

jack vines

[Mike Van Veghten]

Check Jacks last comment.

Mike

[mbstude]

John's car is an R2+ with AC, and a 5 speed.

[PackardV8]

John's car is an R2+ with AC, and a 5 speed

OK, now we have enough data to begin to think.

The solenoid, AKA as throttle kicker, was added primarily for AT cars with AC. If a manual transmission car idles satisfactorily in gear with the clutch depressed and the AC on, a solenoid or vacuum valve isn't needed. If when the AC engages, the idle speed drops to an unstable level, then yes, it's needed.

Question - is there an electric cooling fan? Those often have high amperage draw and can drag down idle speed. Usually, it runs when the AC is engaged, so should be factored in.

Also, is there any difference in dying on decel when in gear versus clutch depressed? Braking in gear produces very high vacuum, which pulls over more fuel.

Have you checked the A/F ratio with a wide-band O2 sensor? If it's on the rich side at cruise, the high vacuum decel will be too rich.

Bottom line - again, if it idles at rest under full AC/electric system load but dies upon decel, usually it is the float level setting is too high.

jack vines

[okc63avanti]

The car idles fine with or without AC most of the time with the exception of after I've been driving for a while and then it sits for 15~20 minutes. Then it is a little hard to start and doesn't want to idle high enough. When this happens I often have to sit at red light with right foot on brake and toes on the accelerator peddle to bump it a little if needed to get it to hold idle. The engine stalling under rapid acceleration happens when braking hard (it doesn't matter if AC is on or not).

My car has the old Stude AC kicker on it (but it isn't working) and with the Sanden compressor vs. original factory York, I'm not sure I really need it. The original Carter AFB did have the idle compensator however, but it isn't on my new Edelbrock.

[PackardV8]

Once you've confirmed both floats are properly set and you have confirmed the fuel pressure isn't more than 5-6#, if it still stalls on decel, there exists a decel valve which can be added. It is basically a diaphragm and a spring which slows the return of the throttle to the idle stop. It's inexpensive and easy to add.

jack vines

[SN-60]

To: okc63avanti,----- This problem is all about the missing throttle kicker.....it really needs to be there! (Studebaker knew that, which is why they used it!) The kicker will bolt up on this Edelbrock as it would with the
original Carter.....question is .....is there a 'tang' on the Edelbrock linkage to accomadate the kicker? Look at the original Carter, or a picture of same, and You will see it. DON'T TAKE THIS CARB APART!!

[jlmccuan]

If you put the vacuum actuated throttle kicker, it will take care of your need to keep bumping the throttle for you. When the engine vacuum drops as the engine stumbles, the kicker opens the throttle slightly to keep it running. That isn't the problem, but it willmake it more driveable until you sort it out.

Both the Edelbrock and the Carter carbs are simple to work on, there is no magic in the box that pours out when you open them up. Edelbrock has a setup and tuning pdf on their website. Take your time, and if you need to, take pictures as you open it up. Setting the floats is very simple.

How did John address the brass floats collapsing under boost? I think he uses the nails soldered in as braces, but take a look at them to see if you've collapsed them a little resulting in the float lagging behind the fuel flow and not closing the needle valve qujickly enough.

[SN-60]

To: okc63avanti,------Buy a new throttle kicker..........You will smile! (and leave that carb alone)