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Old 08-15-2002, 06:03 AM
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Post Crankcase Ventilation

In a previous posting, I queried about (a relatively small amount of) smoke coming out of the breather element on the left valve cover.

It was suggested that a faulty crankcase ventilation system was to blame. But here's my question:

How can this be expected to harm engine performance? It is obvious that these gases aren't harmfully building up in the crankcase.

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Old 08-15-2002, 06:43 AM
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It won't harm your engine but the tree-huggers will suffer irreparably. Actually, CVR valves do some real good by recyclicng unburned hydrocarbons back into your engine to be burned. May be too small to measure but this is like free fuel!
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Old 08-15-2002, 06:44 AM
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Well before they invented the PCV system they all vented into the atmosphere. Any harm? Mostly the atmosphere. But there are definately some supposed advantages to using a PCV system. With a PCV system you are less likely to develope oil leaks in weak seals or gaskets because there's a constant vacuum signal applied to the crankcase instead of blow-by pressures. You always have fresh air being drawn through the engines crankcase. And by removing those pressures from the crankcase I would bet there might be a slight hp gain showed on a dyno, don't know specifics on hp gain though (never was that interested). I always try and use a functioning PCV system mainly to help ensure long seal and gasket life.
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Old 08-15-2002, 07:40 AM
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Thanks for the replies.

I have to do some investigating, but it appears as though my car doesn't even have a PCV system. I wonder why the previous owner would want to do away with the device.
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Old 08-15-2002, 07:59 AM
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Unfortunately I can't remember when they started using PCVs. My manuals are all packed as I'm closing on my house this afternoon and moving. If your car didn't originally use a PCV you could try using newer valve covers with fittings for PCV in one cover and a breather in the other. If the engine is currently running with no PCV and you add one to the system you will be leaning out the fuel mixture. She may be jetted enough to handle the slightly leaner condition or you may have to re-jet her. When I was younger we used to can the PCV to richen the fuel mixture. It was cheaper than re-jetting those junky factory emission friendly carbs. But like I said, not verry good for the oil leaks.
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Old 08-15-2002, 08:07 AM
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Does it matter which side is PCV and which is breather? I run 2 breathers, and plan to go PCV on one side.
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Old 08-15-2002, 08:20 AM
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As far as I know makes no diference.
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Old 08-15-2002, 08:29 AM
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Congratulations on the new house


The engine in my car (a 350) is from a '72 Nova. I imagine PCVs were around then. But it appears as though I have breathers on both sides.

Is the PCV system (hose, valve) supposed to go from the valve cover to the intake manifold?
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Old 08-15-2002, 08:31 AM
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I didn't have a PCV system on my 350 either until last night. As I drove with the windows down I could smell oil and could see the vapors coming out of the breather that was installed and out of the dipstick tube. With the system installed, no more oder. I also noticed a slight drop in oil pressure, not sure why, but my readings are high at 80 at startup and 70 driving at warmup. Goes down to about 10 at idle after warmup. If nothing else it makes me feel good to get the harmful vapors out of the crankcase and burnt through the carb.

I drilled a hole in the valve cover, insurted a grommet with a 3/4" opening and used a standard pcv valve for a 350. I used a 3/8" hose from the pcv valve to the lower 3/8" port in the base of my carb. The port has consent vacuum. It works great.

[ August 15, 2002: Message edited by: Mertz ]</p>
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Old 08-15-2002, 08:49 AM
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Looks like that'll be something I'll have to do.

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Old 08-15-2002, 08:30 PM
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Please be advised that you need a baffle at the PCV valve in the rocker cover so that it will not draw engine oil into the intake manifold.

The first year for PCV was 1963 (1961 for CA). A road draft system was used before that.
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Old 08-16-2002, 04:55 AM
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There is a PCV vaccum hose available from GM (3981058) that has a nintey-dgree bend and is about two foot long that be be modified (cut to fit) for most older applications.

It is fume resistant and will not collapse like heater or fuel hose.
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Old 08-16-2002, 05:15 AM
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Is there any reason, which you could guess, for the previous owner to remove this device?

Isn't it kind of odd that I've got smoke chugging up from only the left side?
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Old 08-16-2002, 05:19 AM
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By the way (and this will really show my ignorance) is it possible that the PCV hose comes from a different spot than the valve cover?

I'm embarrassed to say, but there are several hoses for which I have no idea the function of.
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Old 08-16-2002, 05:45 AM
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The original '66 system (V8) had a breather hole cast into the back of the block next to the distributor. The intake manifold also had an oil filler tube. GM did away with both after '67. Your 350 block doesn't have the breather hole and you probably don't still have the old style intake.

I've never seen a PCV valve located anywhere but the valve cover. Most car installations had the PCV on the front side of the driver's cover and ran the hose to the carb. The air inlet hole was on the rear of the passenger cover with a hose to the air cleaner.
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