The Ford Barn

700rpm · 03-06-2018, 12:05 AM

I’ve had original carbs where the venturi was so tight I could barely remove it, and others where it was so loose it fell out. Does the fit of a venturi affect the performance of the carb? Would a loose venturi change the air flow dynamic and gas mixture, and hence the gas mileage?

Ron in Quincy · 03-06-2018, 01:55 AM

Ray,

As long as the venture is not damaged it should not effect the gas mileage, the venture is sealed by the housing gasket. I believe having the opening of the jets to be proper size and most important for good gas mileage.

I size my jets so you can close off the GAV as soon as the engine is warmed up; driving with the GAV open even 1/4 turn will effect gas mileage.

The Owner Manual tells you to close off the GAV for gas mileage.

Ron

1930-Pickup · 03-06-2018, 03:26 AM

'Imagineers' is what Disney Corp calls their engineers. Is 700rpm implying something here?

johnbuckley · 03-06-2018, 03:58 AM

Quote:

Originally Posted by 700rpm

I’ve had original carbs where the venturi was so tight I could barely remove it, and others where it was so loose it fell out. Does the fit of a venturi affect the performance of the carb? Would a loose venturi change the air flow dynamic and gas mixture, and hence the gas mileage?

I agree with Ron in Quincy. and I reckon that Venuris have to be pretty badly damaged to affect normal performance.

BillCNC · 03-06-2018, 01:06 PM

When one has their Carb air balanced, a .250" grove is also into the face of the bottom casting and a .125" grove is cut around the venturi purposely letting air in the bowl. A .0625" hole is also drilled from the bowl to the ring cut in the venturi allowing air to be transfered.

If you have a venturi that falls out, and you don't want to replace it, wrap a couple pieces of fine thread dental floss around the venturi, rub some oil on it letting it become saturated and reinstall the venturi.

I myself bought a new venturi but this was a method explained to me by an old "A" guy that I got to chatting with at one of the parts houses here in SoCal.

Regards
Bill

Anteek29 · 03-06-2018, 02:05 PM

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Quote:

Originally Posted by BillCNC

When one has their Carb air balanced, a .250" grove is also into the face of the bottom casting and a .125" grove is cut around the venturi purposely letting air in the bowl. A .0625" hole is also drilled from the bowl to the ring cut in the venturi allowing air to be transfered.

If you have a venturi that falls out, and you don't want to replace it, wrap a couple pieces of fine thread dental floss around the venturi, rub some oil on it letting it become saturated and reinstall the venturi.

I myself bought a new venturi but this was a method explained to me by an old "A" guy that I got to chatting with at one of the parts houses here in SoCal.

Regards
Bill

Thanks Bill...I have a Zenith with a really loose venturi. I will try the dental floss trick on mine

BillCNC · 03-06-2018, 02:14 PM

Alan,

A wrap around the top about .375" under the ring and one about at .375" from the bottom of the venturi should do it. If it starts to slide, "TAC" it down with a tiny drop of super glue and I mean TINY, about 1/4 of a drop at 180° from each other. If you can visually see the glue you have to much. blot off the extras quickly before it sets.

ANOTHER method would be to glue the thread in place all the way around and then sand in the needed diameter. Super glue is not permanent and dissolves by soaking it in acetone. HECK, Super Glue even dissolves in water in if you soak it for a day or two. Ad Glycerin to the water and it will break down in an hour or so, ... or scrape it off with a razor blade if you change your mind.

Regards
Bill

03-06-2018, 12:05 AM	#1
700rpm Senior Member Join Date: May 2010 Location: Portland, Oregon Posts: 5,902	A venturi question for you imagineers. I’ve had original carbs where the venturi was so tight I could barely remove it, and others where it was so loose it fell out. Does the fit of a venturi affect the performance of the carb? Would a loose venturi change the air flow dynamic and gas mixture, and hence the gas mileage? __________________ Ray Horton, Portland, OR As you go through life, keep your eye on the donut, not the hole.

03-06-2018, 01:55 AM	#2
Ron in Quincy Senior Member Join Date: May 2010 Location: Quincy, CA. Posts: 1,708	Re: A venturi question for you imagineers. Ray, As long as the venture is not damaged it should not effect the gas mileage, the venture is sealed by the housing gasket. I believe having the opening of the jets to be proper size and most important for good gas mileage. I size my jets so you can close off the GAV as soon as the engine is warmed up; driving with the GAV open even 1/4 turn will effect gas mileage. The Owner Manual tells you to close off the GAV for gas mileage. Ron

03-06-2018, 03:26 AM	#3
1930-Pickup Senior Member Join Date: Mar 2017 Location: southern California Posts: 725	Re: A venturi question for you imagineers. 'Imagineers' is what Disney Corp calls their engineers. Is 700rpm implying something here? __________________ *"That's my wild unsubstantiated guess, and I'm sticking to it regardless of the facts!"*

03-06-2018, 01:06 PM	#5
BillCNC Senior Member Join Date: Aug 2017 Location: SoCal Desert Posts: 826	Re: A venturi question for you imagineers. When one has their Carb air balanced, a .250" grove is also into the face of the bottom casting and a .125" grove is cut around the venturi purposely letting air in the bowl. A .0625" hole is also drilled from the bowl to the ring cut in the venturi allowing air to be transfered. If you have a venturi that falls out, and you don't want to replace it, wrap a couple pieces of fine thread dental floss around the venturi, rub some oil on it letting it become saturated and reinstall the venturi. I myself bought a new venturi but this was a method explained to me by an old "A" guy that I got to chatting with at one of the parts houses here in SoCal. Regards Bill Last edited by BillCNC; 03-06-2018 at 01:11 PM.

03-06-2018, 02:14 PM	#7
BillCNC Senior Member Join Date: Aug 2017 Location: SoCal Desert Posts: 826	Re: A venturi question for you imagineers. Alan, A wrap around the top about .375" under the ring and one about at .375" from the bottom of the venturi should do it. If it starts to slide, "TAC" it down with a tiny drop of super glue and I mean TINY, about 1/4 of a drop at 180° from each other. If you can visually see the glue you have to much. blot off the extras quickly before it sets. ANOTHER method would be to glue the thread in place all the way around and then sand in the needed diameter. Super glue is not permanent and dissolves by soaking it in acetone. HECK, Super Glue even dissolves in water in if you soak it for a day or two. Ad Glycerin to the water and it will break down in an hour or so, ... or scrape it off with a razor blade if you change your mind. Regards Bill Last edited by BillCNC; 03-06-2018 at 02:19 PM.