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Old 06-09-2012, 05:32 PM
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PCV Valve

I just got my 351 Windsor running and it runs well. I have breathers on the valve covers and one of the breathers has a hose going to the vacuum port on the front of the carb. It appears to have too much oil pressure or something as it is blowing oil out past the dipstick and out the valve breathers. Do I need a PCV valve as well as the breather that is vented into the port on the carb or what would work to stop the blowby? Thanks..

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Old 06-09-2012, 05:54 PM
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Quote:
Originally Posted by LBL
I just got my 351 Windsor running and it runs well. I have breathers on the valve covers and one of the breathers has a hose going to the vacuum port on the front of the carb. It appears to have too much oil pressure or something as it is blowing oil out past the dipstick and out the valve breathers. Do I need a PCV valve as well as the breather that is vented into the port on the carb or what would work to stop the blowby? Thanks..
Not too much oil pressure, but I'll bet that vacuum port is plugged. Do you have vacuum at PCV?
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Old 06-09-2012, 05:58 PM
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How So

Do I just pull the hose off and check for vacuum? Is this something that is common? The manifold is a new Edelbrock and the carb is used but I cleaned everything up before I installed it .
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Old 06-10-2012, 08:01 AM
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You need a PCV system... the hose from the breather is just designed to be hooked to the stock air cleaner. Without a PCV system you'll blow gaskets and lots of leaks...don't run the engine until you get that fixed.
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Old 06-10-2012, 08:54 AM
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Sorry to inform you, but the Edelbrock valve covers have very poor oil control baffles letting oil escape into the breathers and pcv valve(at least mine were).
A stock type baffle such as these(see pic) will greatly reduce the amount of oil blowing out.
Maybe you can adapt a stock type baffle from a salvage yard set of covers to work.
There are some aftermarket rubber baffles that insert into the valve cover like the grommet for the pcv valves that are better than the Edelbrock baffles, but not as good as the OEM type.
There are also baffles/separators that plug into the pcv grommet like a pcv valve that may be your best alternative. I can't say that I have had any experience with these(http://www.summitracing.com/parts/EDL-4410/)
FWIW
ssmonty
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Old 06-10-2012, 09:52 AM
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Mojo

What is a PCV System ? The valve covers have baffles in them, possibly they're not graet but they do have a baffle system in them, but that wouldn't be the cause of the oil being pushed out the dipstick tube .
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Old 06-10-2012, 10:20 AM
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Quote:
Originally Posted by LBL
What is a PCV System ? The valve covers have baffles in them, possibly they're not graet but they do have a baffle system in them, but that wouldn't be the cause of the oil being pushed out the dipstick tube .
PCV is positive crankcase ventilation. It relieves the pressures built up in the crankcase from combustion that finds its way past the cylinder rings.

Under vacuum the PCV stays closed. If there is not enough vacuum it could stay open and act as a vacuum leak. So there are some high performance cars that run without them.

In the old days before the PCV engines were allowed to leak everywhere.
Also keep you breather on your opposite valve cover to where have the PCV.
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Old 06-10-2012, 11:38 AM
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I Thought I Did

I thought I had a crankcase venting system when I put the hose from the valve cover breather into the vacuum port at the front of the carb. I am going to post a pic of my setup if I can figure it out or you can look at my photo journal to see how I am set up ..
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Old 06-10-2012, 03:14 PM
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Pressure

I put a PCV valve in and ran the hose to the front port on the carb. When I run the engine, there is vacuum at the port but when I pop the PCV valve out , there is still a considerable amount of pressure trying to pop the valve out. I really have no idea whe to do next and appreciate any and all suggestions ...Thanks
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Old 06-10-2012, 04:12 PM
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Quote:
Originally Posted by LBL
I put a PCV valve in and ran the hose to the front port on the carb. When I run the engine, there is vacuum at the port but when I pop the PCV valve out , there is still a considerable amount of pressure trying to pop the valve out. I really have no idea whe to do next and appreciate any and all suggestions ...Thanks
The PCV valve has to be sealed to a grommet placed into a hole in the valve cover on one side. The hose from the PCV runs to the front of the carb.

The other valve cover uses either a breather, or a hose sealed to a grommet in the valve cover that runs to the air cleaner.

http://www.aa1car.com/library/pcv.htm
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Old 06-10-2012, 05:49 PM
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Cobalt

That's the way I have it now and there's still pressure when I pull the pcv valve out of the grommet. Are there different size PCV valves ?
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Old 06-10-2012, 05:59 PM
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Is this a new build? If so, the rings need to get so time on them to seal/break-in and the blow-by will decrease unless one or more are broken(hope thats not the case).
If its an older engine you may need to perform a leak-down test to see if the rings are wore out.
If its new keep an eye on the oil level.
FWIW
ssmonty
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Old 06-10-2012, 08:45 PM
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It is

It is a new build, I have probably only ran it for 30 minutes or so, how long to break in a set of rings? In the mean time, do I just accept that it's going to have wore crankcase pressure and drive it anyways, will it damage seals or anything like that ?
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Old 06-11-2012, 02:21 AM
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Quote:
Originally Posted by LBL
It is a new build, I have probably only ran it for 30 minutes or so, how long to break in a set of rings? In the mean time, do I just accept that it's going to have wore crankcase pressure and drive it anyways, will it damage seals or anything like that ?
When you say there's "pressure when I pull the pcv valve out of the grommet", do you mean there's pressure blowing out of the valve cover (abnormal if excessive) or that there's vacuum sucking at the end of the PCV valve (normal)?

If the cylinder hone and finish matches the rings and you are using moly rings, they are already broken in by 30 minutes, if things are as they should be. If you have plain cast iron rings, they, too, should be broken in by now, or close to it- but either type will be sealing better after breaking in the engine properly. More here.

If for some crazy reason chrome rings were used, they can take longer to fully seat, but the chances are slim chrome rings were used.

If the bore finish is wrong- either the crosshatch angle or the 'roughness'- the rings can take from a little longer to break in, to NEVER breaking in. If the rings were installed upside down, the engine will have oil and blowby problems that will never resolve. If the block wasn't rebored, there may be so much taper that the rings can't seal. Details will help.

As far as running it as-is, the main concern will be plugs fouling, oil consumption and detonation from the fuel/air mixture being diluted w/oil. You will need to run it at least long enough to break it in. Beyond that, if the problems don't subside you will be chasing your tail until you go back in and fix the problem(s).

You can use a leak down tester to see if the problem is isolated to one cylinder. A compression test might help to show if there is a bad hole as well.

Last edited by cobalt327; 06-11-2012 at 02:33 AM. Reason: Add link.
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Old 06-11-2012, 07:05 AM
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Moly

I used moly rings when I rebuilt it . I may be a little shy of 30 minutes when I think about it , we may have only ran it for 10 or 15 minutes so I'll run it some more today and see whta it's doing .
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