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Jul 21st, 2025 | | | | Joined: Apr 2005 Posts: 38 Wrench Fetcher | | Wrench Fetcher Joined: Apr 2005 Posts: 38 | I have a question regarding the difference in the 1954 6 clyinder valve cover and 55-57 valve covers. The valve covers appear exactly the same except the 1954 has 4 vent slots on the top which later ones do not. Now the oil fill cap I am using on the 54 is the flat type....what is the reason for the vent holes and does it relate to the down draft tube and the oil cap used?
I have a REALLY nice valve cover from a 55 than I want to use on the 54 engine but not sure if the vents are absolutely necessary.
Thanks for the clearification | | | | | Joined: Feb 2004 Posts: 28,675 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 28,675 | The slots are the air source for ventilation. At speeds above 30 MPH, the airflow past the end of the road draft tube creates enough vacuum to pull air out of the crankcase. The air coming into the valve cover supplies the flow that ends up coming out of the draft tube. Use a vented oil fill cap to get the same result from the non-slotted cover.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Sep 2001 Posts: 29,262 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,262 |
The slits in the 54/55 valve cover were to allow "breathing" when using the standard flat valve cover cap (non-breathing cap).
The are a few disadvantages in this 54/55-1st only set-up which are avoided with the later valve covers with no slits and using a breather-cap.
| | | | | Joined: May 2005 Posts: 331 'Bolter | | 'Bolter Joined: May 2005 Posts: 331 | Tim,
What are the disadvantages besides the possibility of water leaking in the rear slits from the cowl vent tube?
Samantha | | | | | Joined: Sep 2006 Posts: 3,597 'Bolter | | 'Bolter Joined: Sep 2006 Posts: 3,597 | The cowl vent tube as seen in this page from the 1954 Factory Assembly Manual does not go straight down on the cover but is set at 45 deg offset +/- 10 deg to avoid water ingress. http://good-times.webshots.com/photo/2377893620102454676eobulj | | | | | Joined: Feb 2004 Posts: 28,675 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 28,675 | Since there is no way to filter the air being introduced into the valve cover, dust and moisture can enter the engine and contaminate the oil. When Commiefornia decreed that all cars on the road had to be retro-fitted for PCV valves in the late 1970's, the conversion kits we sold had a fresh air tube that was attached to the "clean" side of the air filter to provide filtered air to the crankcase.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Sep 2001 Posts: 29,262 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,262 |
Samantha,
You and HrL described the two major disadvantages: water getting in the slits and unfiltered air getting in the slits. Also, the area around the slits sometimes get a little oily/dirty.
The major obvious disadvantage is water getting in - you have to cover the slits if/when you ever use water-spray to clean/rinse the engine.
As Brad showed, the cowl-vent drain-tube should direct water away from the slits (If installed correctly). I put a removable extension-hose on my cowl-vent drain-tube to dump the water right to the ground (if/when I get anal, the hose comes off easily for shows).
| | | | | Joined: Apr 2005 Posts: 38 Wrench Fetcher | | Wrench Fetcher Joined: Apr 2005 Posts: 38 | Well thanks much for the lesson. It all makes sense now. Even the valve cover on my 31 chevy has slits in it as well so now I know. I was able to take a dremmel with a circular cutting blade and carefully cut 4 slits as needed.
Thanks to all !
John Lanning | | |
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