Blowing valve cover gaskets!

1959 - 1978, M151, M151A1, M151A2, Technical questions and discussions, regarding anything related to the M151.
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steveperryman
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Blowing valve cover gaskets!

Post by steveperryman » Fri Nov 12, 2021 3:16 pm

Hi, I have a 1964 m151, I recently have been trying to get it running smoother, I adjusted the timing and the carb settings. Since then, I have high pressure in the valve cover. It idles great, when I remove the valve cap, a lot of pressure blows out, when I drive it, the back valce cover gasket breaks out and it spurts oil...

I know the simple solution is to just vent the valve cover, is that the correct way to resolve this

thanks

-Steve


Fil Bonica
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Re: Blowing valve cover gaskets!

Post by Fil Bonica » Fri Nov 12, 2021 5:22 pm

Have you checked the pcv valve ?
Isnit blocked ?
Do you have a fording valve that is closed?
Either could cause pressure build up in valve cover and ultimately in the engine.

Fil Bonica

steveperryman
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Re: Blowing valve cover gaskets!

Post by steveperryman » Sat Nov 13, 2021 5:01 am

Uh oh.. PVC valve ???? Well look at that, no PVC valve... I'll hunt around for diagrams on how and where its connected. I'm sure I have one and the associated plumbing in my pile of parts . Thanks Fil...

-Steve

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Re: Blowing valve cover gaskets!

Post by Fil Bonica » Sat Nov 13, 2021 5:08 am

Should be as a part of U shaped plumbing from balve cover to top of carb fitting .


Fil Bonica

markrdje
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Re: Blowing valve cover gaskets!

Post by markrdje » Sat Nov 13, 2021 9:19 am

[attachment=PCV VALVE.png[/attachment] I couldn't delete EGR valve
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EGR VALVE.png
change user name to mark

Rickf
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Re: Blowing valve cover gaskets!

Post by Rickf » Sat Nov 13, 2021 2:21 pm

Also make sure the valve cover is actually setting down on the gasket. There is an inner and outer metal lip on the valve cover and for some reason in the back passenger side corner they always seem to get hung up on that lip. You need to wiggle it around and hake sure it totally drops down on the gasket. Once on the gasket it will NOT move side to side. If that is definitely not the problem then I second the PCV valve and if it has a fording valve make SURE it is in the open position.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

steveperryman
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Re: Blowing valve cover gaskets!

Post by steveperryman » Sat Nov 13, 2021 2:30 pm

Yeah, its the lack of PVC ...

I have most of the parts, Fil is hinting for a carb connector, and I need to make some of the plumbing...

Thanks..

-Steve
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PXL_20211113_135028907-min.jpg

Rickf
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Re: Blowing valve cover gaskets!

Post by Rickf » Sun Nov 14, 2021 4:19 am

Ok, So where is that line from the valve cover going? And what is the hole in the oil fill cap? I am thinking that even though there is no PCV that the crankcase is probably vented, not properly but vented just the same and should not be lowing seals. The valve cover gasket is not the one that is blown out from crankcase pressure unless it is already leaking. pressure leaks are from the front and rear crankshaft seals.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

steveperryman
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Re: Blowing valve cover gaskets!

Post by steveperryman » Sun Nov 14, 2021 4:49 am

OK, don't laugh, this is embarrassing...

The line you see from the valve cover goes to the crankcase. So before I drilled out the hole, she would blow. Thats the line that should be connected to the PVC valve....

Rickf
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Re: Blowing valve cover gaskets!

Post by Rickf » Sun Nov 14, 2021 12:47 pm

Nothing to laugh at. You figured out that it was crankcase pressure didn't you? So you were on the right track. For many, many years vehicles did not have PCV valves and the crankcase vented through a tube going out the bottom of the car generally coming out of the valve cover. PCV is THE earliest emission control. What you were doing there was imitating a fording valve. That is exactly what a fording valve does, it closes off the PCV valve and blocks any venting of the crankcase so that pressure will build in the engine and that way not water can get in what underwater. That is why there are all kinds of warnings to release the fording valve as soon as you are out of the water.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone


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