(800) 853-2651
SHOP NOW

I didn't expect this ...

J

jCarroll

Well-known Member
Location
mid-Ohio
1945 Farmall BN, recently new to me.
4 cylinder gas, updraft carb
I was checking manifold vacuum. Port is just above the carb flange on the intake manifold.
Used clear plastic tubing from the manifold to the gage.

At idle a small bit of liquid gas "backed" into the tubing.
Goosing the engine sucked it out - return to idle and the gas would reappear.

I've never seen inside an intake manifold, but I assumed the gas was fully atomized.
What caused the condition I was seeing?
 
Might be the intake manifold was a bit cold. It's not unusual for the outside of carburetors and intake manifolds to frost up when idling in cold damp weather.
 
It's not fully atomized, at least not for long.

It tends to condense to the inside walls of the intake, especially when the engine and weather is cold, and at idle as the mixture is moving slow.

It also tends to track outward in the curves at higher velocity. Inertia wants to send it straight, when it has to go around a curve, the heavier gas tends to hug the outside of the curve, falls out of suspension and sticks to the wall.

The result is inconsistent fuel delivery, the closest and most direct cylinders get more fuel than the others.

That's one of the advantages of multi port injection, nothing but air in the manifold, so no separation, condensing, or pooling.
 
(quoted from post at 17:04:48 10/24/18) It's not fully atomized, at least not for long.

It tends to condense to the inside walls of the intake, especially when the engine and weather is cold, and at idle as the mixture is moving slow.

It also tends to track outward in the curves at higher velocity. Inertia wants to send it straight, when it has to go around a curve, the heavier gas tends to hug the outside of the curve, falls out of suspension and sticks to the wall.

The result is inconsistent fuel delivery, the closest and most direct cylinders get more fuel than the others.


That's one of the advantages of multi port injection, nothing but air in the manifold, so no separation, condensing, or pooling.
Click to expand...

And the fact the mixture is heavier than air.... making updrafts very inefficient. But.. since carb floats were very very unreliable, the updraft was the best way to go.
 
As I recall this was one of the advantages of the slant six dodge engine. To tease you a bit I thought goosing referred to poking something living in the rear!! Ok my dad always used goosing as wanting more fuel. LOL
 
I think a goose started it at some ones farm years ago. Dad had a dog who would goose visitors, I guess to get a better sniff. Stan
 

I did have an old 10 hp briggs, flat head. After it warmed up you could see gas molecules when you removed the air filter. Engine would start missing and spark plug would carbon up.

The problem was intake valve seat recession causing the air in carb to run backwards causing a rich condition.

I had to remove the intake valve and grind off some of the valve stem. I had that happen a few times on the old briggs flat head engines.

So if the tractor is running OK, I wouldn't worry. If tractor is missing at an idle I would be checking the valve clearance and compression. Intake valve may be leaking compression back into the intake.
 

The condensation of gas in the manifold, and the subsequent running down and dribbling out of the carburetor air intake is what causes people to think that their old tractor is "flooded" when no gas even made it to the cylinder yet.
 
You must log in or register to reply here.

Similar threads

V
new owner of a 620, will try to update this as we go.
2 3 4
Replies
61
Views
3K
valiant8086
V
G
Marvel-Schebler carb severely OVERfueling
Replies
7
Views
2K
goldwing2000
G
D
It's Alive!! 2010 LP to gas conversion
Replies
4
Views
640
docmirror
D
T
641 runs great but won't idle. Linkage and adjustment ?'s
Replies
5
Views
3K
sunbeam
S
M
throttle/governor queston
Replies
0
Views
391
Mad Farmer
M
Tractor Parts Tractor Manuals

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Copyright © 1997-2024 Yesterday's Tractor Co.

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters
Website Accessibility Policy

Back
Top