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  #16 (permalink)  
Old 10-02-2007, 12:06 AM
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Quote:
Originally Posted by GCD1962

The road draft tube on old motors did not work by "under car air turbulance to suck out the crank case fumes" It was the pressure within the engine that pushed the fumes out. The fumes escaped even when the vehicle was parked and the engine running. It was also the way water in the crankcase was allowed to evaporate out of the engine.
You need to rethink your theory. The position and degree of bevel on the end of the pipe (and air passing over that bevel) dictated expusion (actually a vacuum was created) of crankcase fumes. The engine fan provided the draft at idle.

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  #17 (permalink)  
Old 10-02-2007, 01:11 PM
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Quote:
Originally Posted by KULTULZ
You need to rethink your theory. The position and degree of bevel on the end of the pipe (and air passing over that bevel) dictated expusion (actually a vacuum was created) of crankcase fumes. The engine fan provided the draft at idle.
While your explantation seems correct, this is not they way most worked. While that "theory" might seem to fit for a early V-8 Chev engine, where the tube was at the back of the engine and then exiting near the bellhousing, many engines had the tube located further forward on the engine where little to no air passed over it and was shielded from the fan. No outside air was needed to draw the fumes from the crankcase.
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  #18 (permalink)  
Old 10-02-2007, 04:23 PM
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Quote:
Originally Posted by GCD1962

While your explantation seems correct, this is not they way most worked. While that "theory" might seem to fit for a early V-8 Chev engine, where the tube was at the back of the engine and then exiting near the bellhousing, many engines had the tube located further forward on the engine where little to no air passed over it and was shielded from the fan. No outside air was needed to draw the fumes from the crankcase.
I'll let the CHEVY crack go as you must be new here...

If you simply google crankcase ventilation, you will come across many sources explaining the old road draft system. The way the tip of the tube is beveled is what creates a vacuum at the outlet thereby creating an air flow within the crankcase, fresh air being ingested via the open oil filler cap. It matters none where the tube was located on the engine as long as it extended down into the air flow.

If internal pressure was the source of the ventilation, it would soon pump most of the engine oil out leaving one heck of a mess. In fact, that is the basic sign of an inoperative system.
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Old 10-02-2007, 05:20 PM
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You guys are full of useful info.
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Old 10-02-2007, 06:06 PM
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Quote:
Originally Posted by KULTULZ
I'll let the CHEVY crack go as you must be new here...

If you simply google crankcase ventilation, you will come across many sources explaining the old road draft system. The way the tip of the tube is beveled is what creates a vacuum at the outlet thereby creating an air flow within the crankcase, fresh air being ingested via the open oil filler cap. It matters none where the tube was located on the engine as long as it extended down into the air flow.

If internal pressure was the source of the ventilation, it would soon pump most of the engine oil out leaving one heck of a mess. In fact, that is the basic sign of an inoperative system.

Just because something is "Googled" and you find a number of listings, does not in itself mean what you are reading is correct. When the draft tubes were introduced one engines, there were no wind tunnels to test the flow, nor was there any attempt. Look at an old Chev 6, pre-war, or a post-war Kaiser, these tubes were located towards the front of the engine where little to know air flow would be created. The tubes were raised well above the crankcase and there are baffles both inside the engine and inside the tube to prevent excess oil from being pumped out. Read an old Chev 6 cylinder manual and you will find that the primary purpose of the draft tube was to allow the vapors from water (condensation) inside the crankcase to evaporate as the inside of the engine came up to temperature. Your theory is just that as the air flow underneath the car could just as easily create a flow that would go around the tube entirely. I suggest you take a good look at some of the older cars next time you are at a show and where the draft tubes are located.
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Old 10-03-2007, 12:49 AM
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...i give up...
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Old 10-03-2007, 10:23 AM
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Kultulz, don't give up when you're ahead. You are exactly correct in your discription of the draft tube. It's called a "draft' tube because it functions as you explained. I'm 73 and my father owned a garage when I was growing up. I spent summer vacations as the mechanic's grunt and gofer. I've cleaned more of thes tubes and the associated oil fill breather cap than anyone else in the world has seen. Tell your critics that the draft tube works the way airplanes fly: Bournelli's principal. (Maybe I spelled his name right)
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  #23 (permalink)  
Old 10-03-2007, 01:49 PM
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Quote:
Originally Posted by Will H

I've cleaned more of thes tubes and the associated oil fill breather cap than anyone else in the world has seen.
It's just that I am too old to argue anymore...

I also have cleaned many and those cartridge oil filters...forgot about oil bath air cleaners... were something too....


  • Non Self-adjusting brakes...


  • Adjust and lubricate the clutch linkage...


  • Complete chassis lube also...


  • Change to anti-freeze (alchohol) in the winter...water in the summer...


  • Tubes and porterwalls...


  • I remember water pump bearings that had grease fittings...


  • And all of this was repeated every one to three thousand miles...
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  #24 (permalink)  
Old 10-03-2007, 02:19 PM
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Quote:
Originally Posted by KULTULZ
It's just that I am too old to argue anymore...

I also have cleaned many and those cartridge oil filters...forgot about oil bath air cleaners... were something too....


  • Non Self-adjusting brakes...


  • Adjust and lubricate the clutch linkage...


  • Complete chassis lube also...


  • Change to anti-freeze (alchohol) in the winter...water in the summer...


  • Tubes and porterwalls...


  • I remember water pump bearings that had grease fittings...


  • And all of this was repeated every one to three thousand miles...
And most of those "service items" were done as a part of the $1.50 lube job. Then there was the .35 oil, the .45 oil or the stuff that came in the glass bottles with a spout on it for .15 - .25. And did you want ethyl or regular gas? And of course gas was 5 gallons for a buck

My .02 on the discussion. An engine is a big pump. The hot side of the piston was the fuel/air mixture that made it work. An intake valve to let it in and an exhaust valve to let it out On the cold (oil) side, still a pump, you still had a similar change but of air (with no by products of combustion, hopefully) due to the pistons moving up and down in their cylinders. You need an inlet (filler cap) and an outlet (pcv or draft tube). While the draft tube really doesn't need any air going by it to work, it does work much better with that movement to create a very small vacuum for positive flow- which, as described above is Bernoulli's Principle: http://theory.uwinnipeg.ca/mod_tech/node68.html.

Dave
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  #25 (permalink)  
Old 10-03-2007, 11:01 PM
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Quote:
Originally Posted by Irelands child

And most of those "service items" were done as a part of the $1.50 lube job. Then there was the .35 oil, the .45 oil or the stuff that came in the glass bottles with a spout on it for .15 - .25. And did you want ethyl or regular gas? And of course gas was 5 gallons for a buck
Yeah, and frequent tune-ups because of lead. File and set the points, clean and gap the plugs. Adjust the valve lash. Rebuild the carb every year. 6V systems that gave you fits.

At least I saw some of it. People these days don't believe it...
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Old 10-04-2007, 12:09 AM
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I was a part time grease monkey for 6 years in the 50s. We also had to clean with high pressure water under the car because of the caked on mud deposited there from all the dirt roads. You just could not service the cars and pickups otherwise. Don't forget the oil caps on the distributor, the 90 wt in the gear box and the grease cup on the Chevy shift linkage....Doug

Last edited by artsman; 10-04-2007 at 07:18 AM. Reason: word omission
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  #27 (permalink)  
Old 10-04-2007, 06:12 AM
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Quote:
Originally Posted by KULTULZ
Yeah, and frequent tune-ups because of lead. File and set the points, clean and gap the plugs. Adjust the valve lash. Rebuild the carb every year. 6V systems that gave you fits.

At least I saw some of it. People these days don't believe it...
Ain't it he!! to get old and remember minutae like that but forget within 10 seconds why you went upstairs -

( You forgot replacing the brushes in generators every year or so, 3 cylinder, 2 cycle Saabs that needed a quart of oil every tank of gas, Chebbies that needed a regular carbon and valve job and mufflers that lasted about year )

Dave
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  #28 (permalink)  
Old 10-04-2007, 07:47 AM
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Quote:
Originally Posted by Irelands child

Ain't it he!! to get old and remember minutae like that but forget within 10 seconds why you went upstairs -


Quote:
( You forgot replacing the brushes in generators every year or so, 3 cylinder, 2 cycle Saabs that needed a quart of oil every tank of gas, Chebbies that needed a regular carbon and valve job and mufflers that lasted about year )

Dave
The SAAB....One quart of oil and fill 'er up. At least you didn't have to sharpen the chain...

How about the cars that needed an oil change on the front (service station) and two dollars of gas?

"FILL IT WITH ETHYL!"

"I don't think she goes for that stuff..."
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  #29 (permalink)  
Old 03-14-2008, 02:46 PM
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Quote:
Originally Posted by GCD1962
The road draft tube on old motors did not work by "under car air turbulance to suck out the crank case fumes" It was the pressure within the engine that pushed the fumes out. The fumes escaped even when the vehicle was parked and the engine running. It was also the way water in the crankcase was allowed to evaporate out of the engine.
[The warning says, "The last post in this discussion occurred over 100 days ago.
If you have relevant information to add to this thread, please post it ."
I think the following is relevant information].

Quote:
Oldsmobile 1949 Shop Manual 6 and 8

CRANKCASE VENTILATOR

The crankcase in all models is provided with a ventilating system to prevent harmful dilution of the engine oil by water and fuel under normal driving conditions. This system utilizes the crankshaft with its counter-weights as a blower to force the vapors consisting of fuel and water from the crankcase.
The above is the complete entry under the bold header. It appears to precisely support what GCD1962 said.

It may be that later systems utilized under car air flow to enhance crankcase ventilation, but this supposition does not change the base function described above.
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