1963 230 l6. PCV causing lean run - Impala Tech
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post #1 of 4 (permalink) Old 10-27-2019, 10:51 AM Thread Starter
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My 230 is bone stock with an original style Rochester 1 barrel on it. According to original Chevrolet specs, the PCV valve is plumbed to a fitting in an intake runner. Great for evacuation of crankcase pressure, but it creates such a lean situation, that the car won't idle. It's a 3/8" vacuum leak in effect. I have it temporarily plumbed into the air cleaner, but I'd rather die it right.
Anyone else experienced this?
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post #2 of 4 (permalink) Old 10-27-2019, 02:56 PM
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It is going into intake on the original engines (includes V8's) but on the other end of the hose is supposed to be a functioning PCV valve and a tight fitting rubber grommet. Does the PCV rattle? Is your rubber PCV grommet still pliable, and fitting snug to both the body of the PCV but more important: to the valve cover? If not then you have found your vacuum leak.

With a V8 another sore point in the system is the location of the filtered air breather that supplies the replacement volume of air to replace what is sucked up into the engine. People do not understand the function of the PCV system and stick an old school breather in the same valve cover as the PCV valve. This short circuits the air flow and promotes a lean condition.

There shouldn't be a breather in your six cylinder valve cover, for the same reason. It gets it's filtered air from inside the air cleaner (and all connections in hoses and plastic pipe fittings must be air tight). It is the length of the tubing (and the associated fluid friction) that causes the already pressurized crank case gasses to flow to the PCV valve
instead of the replacement air from out side the engine zipping across the valve cover to short circuit the system.

Big Dave
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post #3 of 4 (permalink) Old 10-27-2019, 09:44 PM
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I don't know much about the 6's but the V8's did not use a PCV valve as such, rather what they called a "metered orifice". Which, as far as I can tell, is a fancy way of saying a chunk of metal with a specific sized hole in it.

Looking at my '61 shop manual, Section 8-5 they call it a "ventilation valve, which on 8-6 they show disassembled. Shows a valve and spring arrangement. If you don't have the '61 Shop manual and '63 supplement, you are flying blind. Well worth the money!

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post #4 of 4 (permalink) Old 10-30-2019, 08:59 AM Thread Starter
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I do have the Chevrolet shop manual as well as the 63 supplement. I overlooked the breather orifice. My PCV hose, grommet, etc are in good shape. I used a new PCV valve from a local parts house. As a check valve that prevents a backfire from traveling into the crankcase, it works great. I thought of making an orifice to fit inside the hose but I'll do some digging to see if I can find the correct parts first.
Thanks for the info.


Quote:
Originally Posted by Big Dave View Post
It is going into intake on the original engines (includes V8's) but on the other end of the hose is supposed to be a functioning PCV valve and a tight fitting rubber grommet. Does the PCV rattle? Is your rubber PCV grommet still pliable, and fitting snug to both the body of the PCV but more important: to the valve cover? If not then you have found your vacuum leak.

With a V8 another sore point in the system is the location of the filtered air breather that supplies the replacement volume of air to replace what is sucked up into the engine. People do not understand the function of the PCV system and stick an old school breather in the same valve cover as the PCV valve. This short circuits the air flow and promotes a lean condition.

There shouldn't be a breather in your six cylinder valve cover, for the same reason. It gets it's filtered air from inside the air cleaner (and all connections in hoses and plastic pipe fittings must be air tight). It is the length of the tubing (and the associated fluid friction) that causes the already pressurized crank case gasses to flow to the PCV valve
instead of the replacement air from out side the engine zipping across the valve cover to short circuit the system.

Big Dave
Quote:
Originally Posted by dcairns View Post
I don't know much about the 6's but the V8's did not use a PCV valve as such, rather what they called a "metered orifice". Which, as far as I can tell, is a fancy way of saying a chunk of metal with a specific sized hole in it.

Looking at my '61 shop manual, Section 8-5 they call it a "ventilation valve, which on 8-6 they show disassembled. Shows a valve and spring arrangement. If you don't have the '61 Shop manual and '63 supplement, you are flying blind. Well worth the money!
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