Idling/Stalling Out??? ~baffled!

[John Mathieu]

Here is the situation:

Previously, my 1965 Coupe would constantly stall out during idling. The previous owner, Chris Hewitt, thought there was a vacuum leak. After taking the carburetor off I noticed some of the gasket was raised up a bit but it didn't look like it needed replacement. Since I had the carburetor off, I figured I put the new gasket on. So, after replacing it she idles fine but only during the first 15 minutes of operation, at about 500 rpms. Then, after 20 minutes, I am back to doing a foot dance again when approaching red lights. I have stalled out a few times as well and had a darn time getting her started again! I am baffled. Any ideas??

John

[Chris Burbage]

Re: Idling/Stalling Out??? ~baffled!

John,
I had a similar problem on my 65 when I first bought it. I picked up a vaccum gauge and did a carefule adjustment of the idle mixture screws located on the front of your carb, both sides. You are actually quite lucky to get an idle at 500 rpms. Mine tends to idle better in the 750 to 800 rpm range. Also check your timing. If I remember Chris's 396 had an L88 cam in it and probably does not pull much vacuum at lower rpm's.

[Chris Burbage]

Re: Idling/Stalling Out??? ~baffled!

John,
I had a similar problem on my 65 when I first bought it. I picked up a vaccum gauge and did a carefule adjustment of the idle mixture screws located on the front of your carb, both sides. You are actually quite lucky to get an idle at 500 rpms. Mine tends to idle better in the 750 to 800 rpm range. Also check your timing. If I remember Chris's 396 had an L88 cam in it and probably does not pull much vacuum at lower rpm's.

[Ed Jennings]

Re: Idling/Stalling Out??? ~baffled!

Does the car have a heat riser in the exhaust and is it functional? I'm wondering if the 20 minuet time frame is the length of time that it takes for the heat under the carb to become excessive. I'm thinking that if the heat riser was not opening properly that the heat would build up faster, but it's worth checking.

[Ed Jennings]

Re: Idling/Stalling Out??? ~baffled!

Does the car have a heat riser in the exhaust and is it functional? I'm wondering if the 20 minuet time frame is the length of time that it takes for the heat under the carb to become excessive. I'm thinking that if the heat riser was not opening properly that the heat would build up faster, but it's worth checking.

[TLSmith]

Re: Idling/Stalling Out??? ~baffled!

Sounds heat related either carb is geting to warm or heat expansion is creating a vacum leak. Possibly gasket does not seal totally when warm. Also 500 RPM sounds low maybe to low won't take much gas to increase to 7 or 800.

[TLSmith]

Re: Idling/Stalling Out??? ~baffled!

Sounds heat related either carb is geting to warm or heat expansion is creating a vacum leak. Possibly gasket does not seal totally when warm. Also 500 RPM sounds low maybe to low won't take much gas to increase to 7 or 800.

[Don G.]

Re: Idling/Stalling Out??? ~baffled!

One thing to try is to replace the fuel filter . another easy one is to check for a plugged vent in the gas cap. When it starts to falter, remove the gas cap and see what happens.

[Don G.]

Re: Idling/Stalling Out??? ~baffled!

One thing to try is to replace the fuel filter . another easy one is to check for a plugged vent in the gas cap. When it starts to falter, remove the gas cap and see what happens.

[Duke W.]

Re: Idling/Stalling Out??? ~baffled!

If it's got an L-88 cam it won't idle much below 1200-1500 RPM. That's a pure racing cam that is totallly unsuited for the street. Install the correct SHP cam and make sure everything else is set according to factory spec.

Duke

[Duke W.]

Re: Idling/Stalling Out??? ~baffled!

If it's got an L-88 cam it won't idle much below 1200-1500 RPM. That's a pure racing cam that is totallly unsuited for the street. Install the correct SHP cam and make sure everything else is set according to factory spec.

Duke

[George J.]

Re: Idling/Stalling Out??? ~baffled!

John,

also check the tach against an electronic one. It could be reading high. George #31887

[George J.]

Re: Idling/Stalling Out??? ~baffled!

John,

also check the tach against an electronic one. It could be reading high. George #31887

[Wayne C.]

Re: Idling/Stalling Out??? ~baffled!

Maybe I'm misreading your post, and I don't know your level of expertise, so forgive me if this explanation is too simplistic or insults your level of knowledge...

It's a rare engine that will idle smoothly at 500rpm.

Idle speed has to be set with the engine fully warmed up, after cycling the accelerator linkage to ensure that the choke has fully disengaged from augmenting the accelerator linkage. If it's idling at 500rpm in the first few minutes after you start the car (did I misread that?), the choke is on and holding the accelerator open beyond what should be the warm idle setting, so that when the engine warms enough (that the choke ceases to engage the accelerator linkage), then the rpm drops off and the engine stalls when the accelerator pedal is released. When the engine is cold with the choke fully on, the engine should idle at 1500 to 1700 rpm.

Also, if the choke is not operating correctly, it will tend to "choke" the warm engine with extra fuel, another cause of stalling at idle.

Yet another possibility is that you have a leaky/dirty float needle that is allowing too high a fuel level in the float chambers (a common problem with rusty old fuel tanks or lines) and the engine can't use the fuel as fast as it's spurting in at idle. Look for sooty emissions from the tailpipes at idle.

I think someone mentioned that you also need to check the heat riser valve for free operation of the counterweight.

[Wayne C.]

Re: Idling/Stalling Out??? ~baffled!

Maybe I'm misreading your post, and I don't know your level of expertise, so forgive me if this explanation is too simplistic or insults your level of knowledge...

It's a rare engine that will idle smoothly at 500rpm.

Idle speed has to be set with the engine fully warmed up, after cycling the accelerator linkage to ensure that the choke has fully disengaged from augmenting the accelerator linkage. If it's idling at 500rpm in the first few minutes after you start the car (did I misread that?), the choke is on and holding the accelerator open beyond what should be the warm idle setting, so that when the engine warms enough (that the choke ceases to engage the accelerator linkage), then the rpm drops off and the engine stalls when the accelerator pedal is released. When the engine is cold with the choke fully on, the engine should idle at 1500 to 1700 rpm.

Also, if the choke is not operating correctly, it will tend to "choke" the warm engine with extra fuel, another cause of stalling at idle.

Yet another possibility is that you have a leaky/dirty float needle that is allowing too high a fuel level in the float chambers (a common problem with rusty old fuel tanks or lines) and the engine can't use the fuel as fast as it's spurting in at idle. Look for sooty emissions from the tailpipes at idle.

I think someone mentioned that you also need to check the heat riser valve for free operation of the counterweight.