The Ford Barn

kippmw · 05-18-2023, 08:33 PM

Hi all. I'm scratching my head a little with this one. I have a good Zenith 2 on my car that runs great down the road with good response and power. The idle get's a little odd under certain circumstances. It idles great when the car is on a flat surface or if the car is pointed downhill, but it idles rough when the car is pointed uphill (i.e. on my driveway with the front of the car point uphill). I'm a little confused by this one. Thoughts??

Thanks in advance!
Matt

J Franklin · 05-18-2023, 09:30 PM

Must be the float setting.

kippmw · 05-18-2023, 09:53 PM

Quote:

Originally Posted by J Franklin

Must be the float setting.

That would make sense, except the gas would slosh to the back of the bowl where the jets/passages are, right? Not starving the carb of fuel?

bruceincam · 05-18-2023, 10:05 PM

Not enough fuel flowing from the tank to the carb when you ask it to over come gravity by pointing the flow path up hill.

J Franklin · 05-18-2023, 10:59 PM

There would be plenty of gravity in a model A, but too little or too much gas can cause rough idling.

nkaminar · 05-19-2023, 06:49 AM

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Suggest you point it down hill or keep it on the flats.

Rob Doe · 05-19-2023, 08:16 AM

How steep? And did you tighten the GAV a bit?

CT Jack · 05-19-2023, 08:40 AM

I tend to agree with bruceincam regarding fuel flow from the tank. Have you tried testing in uphill position with a full tank? If it improves the smoothness at idle then you might have a restriction in your fuel tank. A change in head pressure might affect fuel flow when in the uphill position with a low level of fuel.

kippmw · 05-19-2023, 10:36 AM

You'd think it wouldn't run well down the road if there was a fuel flow issue, but it runs great down the road with good power.

Quote:

Originally Posted by bruceincam

Not enough fuel flowing from the tank to the carb when you ask it to over come gravity by pointing the flow path up hill.

kippmw · 05-19-2023, 10:37 AM

Typical driveway steepness of maybe 4-5% grade, so not that steep.

Quote:

Originally Posted by Rob Doe

How steep? And did you tighten the GAV a bit?

kippmw · 05-19-2023, 10:38 AM

It has 3/4 of a tank right now. It runs great down the road with good power, which you wouldn't expect if there was a fuel flow issue.

Quote:

Originally Posted by CT Jack

I tend to agree with bruceincam regarding fuel flow from the tank. Have you tried testing in uphill position with a full tank? If it improves the smoothness at idle then you might have a restriction in your fuel tank. A change in head pressure might affect fuel flow when in the uphill position with a low level of fuel.

Brentwood Bob · 05-19-2023, 12:19 PM

Might change the float. A worn spot above the float valve??

kippmw · 05-19-2023, 01:57 PM

That's a thought. I've got a bunch of floats, so I'll try that. Thanks!

Quote:

Originally Posted by Brentwood Bob

Might change the float. A worn spot above the float valve??

05-18-2023, 08:33 PM	#1
kippmw Member Join Date: Sep 2010 Location: Aurora, CO Posts: 59	Rough Idle When Pointed Uphill Hi all. I'm scratching my head a little with this one. I have a good Zenith 2 on my car that runs great down the road with good response and power. The idle get's a little odd under certain circumstances. It idles great when the car is on a flat surface or if the car is pointed downhill, but it idles rough when the car is pointed uphill (i.e. on my driveway with the front of the car point uphill). I'm a little confused by this one. Thoughts?? Thanks in advance! Matt __________________ 1929 Briggs Fordor 165B 1930 Deluxe Coupe 1966 Mustang 2015 Ford Focus ST

05-18-2023, 09:30 PM	#2
J Franklin Senior Member Join Date: May 2010 Location: Oregon Posts: 5,962	Re: Rough Idle When Pointed Uphill Must be the float setting.

05-18-2023, 10:05 PM	#4
bruceincam Senior Member Join Date: Mar 2021 Location: Camarillo, Ca Posts: 167	Re: Rough Idle When Pointed Uphill Not enough fuel flowing from the tank to the carb when you ask it to over come gravity by pointing the flow path up hill.

05-18-2023, 10:59 PM	#5
J Franklin Senior Member Join Date: May 2010 Location: Oregon Posts: 5,962	Re: Rough Idle When Pointed Uphill There would be plenty of gravity in a model A, but too little or too much gas can cause rough idling.

05-19-2023, 06:49 AM	#6
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,897	Re: Rough Idle When Pointed Uphill Sponsored Links (Register now to hide all advertisements) Suggest you point it down hill or keep it on the flats. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

05-19-2023, 08:16 AM	#7
Rob Doe Senior Member Join Date: Apr 2021 Location: Central Illinois Posts: 491	Re: Rough Idle When Pointed Uphill How steep? And did you tighten the GAV a bit? __________________ "It ain't what you know for certain that gets ya in trouble. It's what ya know for certain that just ain't so!"

05-19-2023, 08:40 AM	#8
CT Jack Senior Member Join Date: May 2010 Location: Hebron, CT Posts: 432	Re: Rough Idle When Pointed Uphill I tend to agree with bruceincam regarding fuel flow from the tank. Have you tried testing in uphill position with a full tank? If it improves the smoothness at idle then you might have a restriction in your fuel tank. A change in head pressure might affect fuel flow when in the uphill position with a low level of fuel.

05-19-2023, 12:19 PM	#12
Brentwood Bob Senior Member Join Date: May 2010 Location: brentwood, ca Posts: 4,241	Re: Rough Idle When Pointed Uphill Might change the float. A worn spot above the float valve??