Road Draft Tube issue

M

markbartlett

Junior Member
I installed a Road draft tube on my model A today. I finished up and started truck and noticed about a 1/2 to 1 inches of vacuum just enough to be able to feel it when you put your thumb over tube. drove it about 15 miles and it developed a leak around rear main area . I checked the road draft tube for obstructions and is free flowing no restrictions. anybody have any ideas where the vacuum is coming from. I am new to these 4 bangers with valves in block . Thanks
 
If you did not have a leak before at the rear main I would take the road draft tube off,Henry did not put one on,lust my opinion.
 
Mikeinnj said:
What pray tell is a road draft tube?
Click to expand...

It's one of these things that plugs into the top of the oil filler pipe and then has a flexible metal tube that goes down under the car. Blow-by from the engine goes out there instead of all inside your engine compartment. In theory, if you are moving forward fast enough, the wind blowing by end of the tube actually helps to pull the blow-by out of the crankcase.

Cars of the 50's and early-60's had them, before they started to install PCV valves on engines to reduce pollution. Fresh air went into the engine somewhere, through a filter, and the draft tube sucked the blow-by out.
 
These?
 

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Welcome to the Barn. How did you put your thumb over the tube? I have heard that sometimes the baffles get kinked in the filler tube and can cause a vacuum. I vaguely remember seeing something about it in the Ford Service Bulletins.

Mike
 
Sounds to me like someone ported a vacuum line off of the manifold to the crankcase to stop a leaky rear seal. When you put the crankcase venting tube in place of the oil filler cap you thwarted the crankcase vaccum and the rear seal started leaking again. Maybe just an insane idea...I don't know, never heard of such a thing. Grasping at straws?
 
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