Draft tube

[pflaming]

Some route the draft tube into the air cleaner. One reason is a 1 mile increase in gas mileage, another is to eliminate oil on the floor. Question: does the air flow through the carb draw the oil into the air filter and is it liquid oil or fumes which cooled return to liquid, and how small can that tube be? 

[JOHN EDGE]

I remove the tube but used the bolt in portion of the tube to mount a #8 hose and run it to a firewall mounted tank with a breather. Works fine. Was tired of the constant oil drips.  See the breather on the far right

[JOHN EDGE]

Little bit better photo

[Merle Coggins]

That looks nice, but it wouldn’t have the scavenging effect that the original draft tube would have. 

[Adam H P15 D30]

I cut my tube to about 4” long, flipped it upside down and put a PCV valve in it. 

[Adam H P15 D30]

On 3/26/2018 at 8:37 AM, JOHN EDGE said:

I remove the tube but used the bolt in portion of the tube to mount a #8 hose and run it to a firewall mounted tank with a breather. Works fine. Was tired of the constant oil drips.  See the breather on the far right

Take the breather off the can, seal it and put a PCV valve in it.

[JOHN EDGE]

Thought about a pcv and looked at the kits that are there. Need to also seal the oil fill tube.  So far things seems to work fine 

[Adam H P15 D30]

Why seal the fill tube?  It needs to breathe in the full tube out through the draft tube or pcv. 

[pflaming]

Interesting: the bottom of the engine requires air, PULLED IN at the fill tube and forced out or PULLED OUT by the draft tube. So then if routed out to the carb, that air flow DRAWS OUT the fumes and uses them as fuel, as little as they might be.

 

Is that a fair statement? 

[Adam H P15 D30]

Perfectly fair statement. That is if you have a vacuum inside your air filter (restricted?). That’s where a metered valve connected to manifold vacuum comes into play. On late model cars a tube was plumbed to the air filter to clean the incoming air into the crankcase. 

[pflaming]

23 minutes ago, Adam H P15 D30 said:

a vacuum inside your air filter (restricted?).

 

So then the air filter needs to be tight and the hose / tube connection from the block tight as well? 

[Adam H P15 D30]

The hose that goes to the air filter traditionally is to filter the air going into the crankcase and it should be snug so dirty air cannot pass, same for the air filter attachment to the carb. The air is sucked out either by the negative pressure at the bottom of the road draft tube or pcv valve connected to manifold vacuum. There shouldn’t be vacuum inside the air filter housing. 

[Adam H P15 D30]

[pflaming]

I do not see the drawing as representatve of my flathead engine.  Is sludge in part the result of water build up in the engine,    no water no sludge? 

[Adam H P15 D30]

No water + detergent oil + longer drives + good venting = no sludge

point of the picture shows clean air enters the crankcase from the air filter and exits opposite through the pcv valve.  Representative of any engine

[Adam H P15 D30]

Upper breather hose would be representative of our oil fill tube. Breather chamber would represent our road draft tube

Edited March 31, 2018 by Adam H P15 D30

[BigDaddyO]

The PCV Valve does 2 things;

1. Meter the amount of air flow from the crankcase to the intake.

B. Closes off the passage way from the intake to the crankcase in the event of a backfire or afterfire.

 

 

https://auto.howstuffworks.com/positive-crankcase-ventilation-system.htm

Edited March 31, 2018 by BigDaddyO
Oops.

[JBNeal]

draft tube replacement based on Chrysler service bulletin