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Aug 12, 2016 | 01:45 PM

#16

JEFFFAFA

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From: Phoenix, Az.

Quote:

Originally Posted by ru67

Here is whats stamped on the intake (cast iron). firing order(rear) and on the front behind the distibutor it has 4E21 and right under that has C4SE9425A.

I was right then.Early 60's Car intake. And yes, that was a road draft tube. It is to vent the crankcase like a PCV system. Only the vented fumes go to the atmosphere rather than being burned through the engine. Depending on what chassis that intake was originally installed in, The road draft tube part number would have been C0AE6758C or C2SZ6758A. Go to page 88 on here
Thunderbird Restoration Guide, 1958-1966

https://books.google.com/books?isbn=1610592212
William Anton Wonder William Wonder
Cars for other states came equipped with the standard, non-emission system, which used a "road draft tube" (#COAE 6758-C) measuring 29 3/4 inches in length,

for the only other pic I can find of it on line. This road draft tube only requires that oil cap to be an unplugged up breather cap. NO PCV system parts.

Aug 12, 2016 | 02:10 PM

#17

Coastal68

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From: Charleston, SC

Quote:

Originally Posted by JEFFFAFA

What would the disadvantage be to the engine of the older method of venting?

Aug 12, 2016 | 02:23 PM

#18

Brian1971f100

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From: Barre Mass

Quote:

Originally Posted by Coastal68

What would the disadvantage be to the engine of the older method of venting?

I don't think the engine cares. It's better for the environment to have a closed system( PCV). The older style will have to be is as it is.

Aug 12, 2016 | 03:46 PM

#19

JEFFFAFA

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From: Phoenix, Az.

Quote:

Originally Posted by Brian1971f100

I don't think the engine cares. It's better for the environment to have a closed system( PCV). The older style will have to be is as it is.

2X Brian. While I was surfing trying to find one or a pic of one, I ran across a bunch of forum threads where some 60's T-Bird guys were trying to convert to a closed PCV system. And having troubles.

Aug 12, 2016 | 07:55 PM

#20

ru67

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Yeah, the PVC system into the valve cover, running into the PVC tube on the carburator spacer plate with a cap put over this large opening (road draft tube) is what i've tried. Now after letting the engine run about 5 minutes it will then start blue smoke coming from the exhaust pipes.I will try leaving that tube open and with only a oil breather cap in the valve cover and plug off the PVC fitting under the carb. Thanks

Aug 13, 2016 | 10:21 AM

#21

JEFFFAFA

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From: Phoenix, Az.

Quote:

Originally Posted by ru67

Make sure that oil cap on the oil fill tube is a breather cap also. And not plugged up from gunk. Back in those days that oil cap usually had metal filtering media in it that reminds me of one of those rough cleaning pads a person would use to clean a kitchen pan with some food burnt on it. People used to use gasoline (with caution) to clean out the metal media in those caps.
Now on the road draft tube. What you should do is fab up a tube that will go around your bell housing and down like it was originally. You see the reason it is called a road draft tube because it's opening should be down in where the air flowing (draft) under your truck is going past while driving down the road. The draft flowing past the opening in the tube will create a vacuum in the tube. This vacuum will pull the built up pressure and/or fumes from the crankcase.

As long as the breather cap is not plugged.

Aug 13, 2016 | 01:25 PM

#22

ru67

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I have a new oil breather cap in the filler tube, but also have chrome valve covers on the engine with a breather cap in the hole on each valve cover. could this be to much as for breather caps ? these chrome valve covers were on it when i bought the truck,so i dont have the stock valve covers.Do the stock valve covers have a breather cap on each one ? something in causing my engine to start smoking blue smoke after it sits an idles for about 10 minutes.It don't smoke when i first crank it,but only after about 10 minutes of running.I can fab me up a tube to take care of the road draft tube.

Aug 13, 2016 | 02:10 PM

#23

JEFFFAFA

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From: Phoenix, Az.

Quote:

Originally Posted by ru67

As long as you leave that rubber cap off the road draft tube nipple you will be all right. Pressure won't build up in the crankcase if you go back to how it was originally. But I still stress fabbing up the rest of the road draft tube. In a shape of a mellow question mark. And then down. a) for the vacuum I suggested above. b) the oil film around that nipple you mentioned is from a bit bigger droplets of oil in the crankcase air that was venting. If you finish out the road draft tube these droplets would have to go up hill before coming out the bottom. Which under normal circumstances they won't do. So they will just gather and drain back down in to the crankcase.