Road draft tube plumbing
 

Need clarification on road draft tube plumbing. Currently, my road draft tube is connected to my air cleaner with what appears to bve an inline PCV valve. I also have a tube from my oil filler connected to the base of my carburetor. The oil filler cap appears to be vented. Is this correct?

Re: Road draft tube plumbing
 

In the original configuration, the road draft hole in the back of the block behind the manifold would have had a hard pipe installed that hung down on the passenger side of the bellhousing. As the vehicle moved down the draft a draft on the bottom of the tube would suck the fumes out of the crankcase. It wasn't a very efficient system.

Your current setup appears to be installed backwards. A PCV (Positive Crankcase Ventilation) valve will not function correctly hooked up to the air cleaner. It must be connected to full manifold vacuum.

If you have the hose adapter in the road draft tube opening now, it should be routed to a PCV valve and connected either directly into the intake manifold (usually behind the carburetor) or directly to the base of the carb at a full manifold port. This is the only way the crankcase will be properly ventilated.

The valve cover can have either an open breather, or a breather with a tube on the side connecting to the air cleaner. You can actually have breathers on both valve covers if desired. The purpose of the breather(s) is to allow fresh air into the engine, while the PCV pulls the fumes out. A breather connected to the base of the carb without a PCV installed will function as a massive vacuum leak and the engine will idle crappy.

Re: Road draft tube plumbing
 

you should have a line with PCV from either the back of the block (for V8's) or the side of the block on the passenger side (for I6's) and you also need a source for intake. That would be the crankcase intake.

I have fixed my Road draft tube conversion.

Here's the thread: http://67-72chevytrucks.com/vboard/s...d.php?t=645971

Re: Road draft tube plumbing
 

Thanks for the responses. So sounds like I need to run the tube from the rear of the engine to the base of the carb with a PCV in line. Do i then run the tube from the oil filler to the air cleaner?

Re: Road draft tube plumbing
 

some photos[ATTACH][ATTACH][ATTACH]Attachment 1387515[/ATTACH][/ATTACH][/ATTACH]

Re: Road draft tube plumbing
 

Yes that is correct. Back of engine to PCV then on to the base of the carb. The breather on the oil fill tube doesn't really need to go anywhere. It just needs to be a "breather" cap, not a sealed cap. This is where fresh air will enter the engine.

Re: Road draft tube plumbing
 

I've got the same style engine in my truck.

Here's what I did, put a grommet and the PCV valve in the hole in the back of the block and will run the hose to the back of the Carb with a hose barb. Then use a breather cap on the fill tube. The original 2bbl carb has a pipe thread where the original PCV valve screwed in, 1/8"? I think?

Grommet: Dorman/Help #42323
PCV Valve: Standard V158


[IMG]http://i269.photobucket.com/albums/j...331_211528.jpg[/IMG]

[IMG]http://i269.photobucket.com/albums/j...5_210720_1.jpg[/IMG]


Sorry about the enormous pictures. Just really trying to get my point across, I guess.

Hope this helps.

Re: Road draft tube plumbing
 

I ran into the same thing with my P.O.S the Exxon Valdez. I'm pretty sure you need the piece inside the galley to make everything work.

Re: Road draft tube plumbing
 

so I found this picture: mine was plumbed as a "closed positive ventilation System" without the flame arrestor and with a vented cap. I'm going to go the top route and use the grommet and PCV.

Re: Road draft tube plumbing
 

I did the pvc conversion too. (Thanks Figarus for the thread) and am enjoying not having "motor stink" wafting thru my vents via the cowel. I never knew pvc hose was a special type until I tried using the wrong kind and saw it collapse from the suction.

Re: Road draft tube plumbing
 

Ok, I didn't want to remove the distributor to use the pcv grommet suggested above. I did find this one part number 46023.

Re: Road draft tube plumbing
 

Part

Re: Road draft tube plumbing
 

I used pcv 158 in conjunction with adapter

Re: Road draft tube plumbing
 

These are the parts I was able to eliminate. Thanks to everyone on this board for their help.

Re: Road draft tube plumbing
 

So is it best to leave the can in the galley even when you retro fit with a PCV at the back?

Re: Road draft tube plumbing
 

Yes!!
It's there as an oil seperator.
Keeps the oil in the motor and only allows the crankcase fumes to flow thru.

Re: Road draft tube plumbing
 

Thank you! I'll take it off to clean only then replace