The Ford Barn

markbartlett · 04-30-2018, 08:28 PM

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

rocket1 · 05-01-2018, 07:47 AM

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 · 05-01-2018, 12:49 PM

What pray tell is a road draft tube?

Charlie Stephens · 05-01-2018, 12:54 PM

I am a little confused about what you are calling a "road draft tube". How about a picture?

Charlie Stephens

Jim/GA · 05-01-2018, 12:58 PM

Quote:

Originally Posted by Mikeinnj

What pray tell is a road draft tube?

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.

burner31 · 05-01-2018, 01:10 PM

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1931 flamingo · 05-01-2018, 01:17 PM

YUP
Paul in CT

1930artdeco · 05-01-2018, 01:44 PM

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

eagle · 05-01-2018, 02:27 PM

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?

04-30-2018, 08:28 PM	#1
markbartlett Junior Member Join Date: Aug 2014 Posts: 5	Road Draft Tube issue 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

05-01-2018, 07:47 AM	#2
rocket1 Senior Member Join Date: Mar 2014 Location: Midland Park,N.J. Posts: 1,108	Re: Road Draft Tube issue 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.

05-01-2018, 12:49 PM	#3
Mikeinnj Senior Member Join Date: May 2010 Location: Northern New Jersey Posts: 1,262	Re: Road Draft Tube issue What pray tell is a road draft tube?

05-01-2018, 12:54 PM	#4
Charlie Stephens Senior Member Join Date: May 2010 Location: Southern California Posts: 7,031	Re: Road Draft Tube issue I am a little confused about what you are calling a "road draft tube". How about a picture? Charlie Stephens

05-01-2018, 01:17 PM	#7
1931 flamingo Senior Member Join Date: May 2010 Location: new britain,ct 06052 Posts: 9,390	Re: Road Draft Tube issue YUP Paul in CT

05-01-2018, 01:44 PM	#8
1930artdeco Senior Member Join Date: May 2010 Location: Lynden, Wa Posts: 3,550	Re: Road Draft Tube issue 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 __________________ 1930 TownSedan (Briggs) 1957 Country Sedan

05-01-2018, 02:27 PM	#9
eagle Senior Member Join Date: Aug 2011 Location: Eagle Bend, MN Posts: 2,025	Re: Road Draft Tube issue 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? __________________ "There are some that can destroy an anvil with a teaspoon and shouldn't be allowed to touch anything resembling a tool." Last edited by eagle; 05-01-2018 at 10:13 PM.