Carburetor fun after ages of letting the old girl cool her jets

[Stoffregen Motorsports]

The dropping off and dying is a concern.  I'm betting it's fuel related, not air or electrical.

[datzenmike]

On 11/14/2023 at 3:50 PM, None_zero said:

I went with oval the holes because the base is where the air/fuel mix is and that is one of the things that seems off (as in doesn't behave as expected) although with the new carb on it doesn't seem to have added any adjustment there. Still sets about the same all the way closed then back out a half turn or so. Haven't had a chance to check if gas mileage has improved yet also air fuel all the way closed still doesn't make it stall out 

 

If working properly turning the idle mixture screw turned in, will lean the fuel and air mix. Turned in all the way will shut off all the fuel but it would have stalled long before that.

 

Turning out the idle speeds screw closes the throttle butterflies reducing the air flow. Engine will idle lower and lower till it can't run at all. Likely not run below 500 RPMs.

 

1/ To set the idle speed and mix thoroughly warm the engine.

2/ Turn the idle down so any changes are easier to notice.

3/ Turn idle mix screw in or out looking for any increase in idle speed. There is about 1/2 a turn where it runs best and turning any farther in or out makes it run poorly. Just set roughly in the middle.

4/ As the idle speed has presumable gone up, turn the idle speed screw out to reduce idle speed.

5/ Repeat 3/ and 4/ until you cannot improve the idle quality further and the idle speed is 650-750

 

If you cannot do this then something is wrong. Most likely a small vacuum leak at a gasket. This lets in air that is not under control by the carburetor.

 

 

 

[None_zero]

3 hours ago, datzenmike said:

 

If working properly turning the idle mixture screw turned in, will lean the fuel and air mix. Turned in all the way will shut off all the fuel but it would have stalled long before that.

 

Turning out the idle speeds screw closes the throttle butterflies reducing the air flow. Engine will idle lower and lower till it can't run at all. Likely not run below 500 RPMs.

 

1/ To set the idle speed and mix thoroughly warm the engine.

2/ Turn the idle down so any changes are easier to notice.

3/ Turn idle mix screw in or out looking for any increase in idle speed. There is about 1/2 a turn where it runs best and turning any farther in or out makes it run poorly. Just set roughly in the middle.

4/ As the idle speed has presumable gone up, turn the idle speed screw out to reduce idle speed.

5/ Repeat 3/ and 4/ until you cannot improve the idle quality further and the idle speed is 650-750

 

If you cannot do this then something is wrong. Most likely a small vacuum leak at a gasket. This lets in air that is not under control by the carburetor.

 

 

 

I yes I tried to run through this checklist I e done this enough times now that I pretty much got the whole process down now. But still no success. When I turn the screw in or out it doesn't really do much. I might get a slight rise or dip in idle speed but then it settles back to where it was. If I adjust it an extreme distance 5-7full turns then I think it would die (turns out that is) turning in i max out amd it still idles . I noticed last time inwas messing with it the choke seemed to be just hanging limp and adjusting the turntable portion....(knob Maybe is what you would call that?or the housing for the bimetal portion of the choke) and seems like I get no change but then maybe when warmed up it is supposed to stay open all the time I can't remember that part. Also when I first hooked it up I had the wires swapped for the solenoid and the choke and I might have fried a relay but I replaced it with one that should be working. And swapped the wires to the correct positions I also think I've still got a vac leak though and the vac advance is still open at the distributor and capped at the hardline. The other thing is I still have a very difficult time idling lower than maybe 700 

Edited November 17, 2023 by None_zero

[None_zero]

I would even say it won't idle at 500 rpms absolutely no way at a 1k it runs without stuttering and and either stalling or sounding like it's gonna stall. I can maybe get it smooth at 800 but any lower and it'll at least sound like it's gonna die and past 700rpms it probably will die 

[None_zero]

Can confirm dramatically increased fuel economy. According to my calculations I went 23.8 miles from the gas station to home and back to another station and had used 1.2 gallons putting my mpg at 19.83 I believe. And home is the half of the trip that's got most of the uphill and I had the bed loaded with cargo probably few hundred lbs at least aside from my own lanky tail so that much is a win for sure 

[Crashtd420]

8 hours ago, None_zero said:

I would even say it won't idle at 500 rpms absolutely no way at a 1k it runs without stuttering and and either stalling or sounding like it's gonna stall. I can maybe get it smooth at 800 but any lower and it'll at least sound like it's gonna die and past 700rpms it probably will die 

I'm not 100% sure but I think the weber's like to idle closer to 750 anyway,  I think 800 is fine.... 

[datzenmike]

Most don't have a tach anyways. 700-800 is fine.

[None_zero]

When you refer to the hot exhaust gasses you mean that get pulled Into the intake via the port on the bottom of the inlet vent before the air cleaner? Cause I don't have that 

[datzenmike]

No, I said...

 

On 11/16/2023 at 10:39 AM, datzenmike said:

You can run without it. My theory is that this is for the first minutes after cold start up before the ATC (air temperature control) kicks in. That's the air heated by the hot exhaust. This would really help vaporize the cold fuel droplets and this would improve unburned hydrocarbon emissions.

 

Perhaps if I had added manifold this would have been clearer. Cold air is mixed with air that is warmed by the hot exhaust manifold. This air is controlled closely to maintain it at about 100F. Carburetor cannot freeze up (called carburetor icing) and the engine runs like it's August all year round.