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Draft tube


pflaming

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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? 

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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

image.jpg

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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

image.jpg

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

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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 

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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? 

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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? 

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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. 

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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 by BigDaddyO
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