Oil Problem

[Ronnie Russell]

Mike, "all gunked up in place you dont want it to ( ie; the underside of the car) ??? So you had rather force that "gunk" into the intake manifold? Im sorry guys, I give up. I guess I cant see the forrest for the trees. I will leave it alone, dont want to lose good friends because of a pcv valve.

 

[JimKwiatkowski]

Ronnie,there's no need to be sorry,you told us the facts and it's up to 29 if he wants his windshield gunked up or his underside

 

[29Coupe348]

well, i changed the breather , and it happened again today....now, im going with the road draft tube, till i get my new motor over the winter...thanks,mike

 

[johnnyrod]

Could we not plumb it like on the 327 250 hp engines. PCV valve from a sealed filler tube to base of carb and a road draft tube from the rear of the engine to the air cleaner that line is about 1/2 inch or even bigger. Just a thought feed back please. John

 

[Ronnie Russell]

Johnny, I think the key is " base of carb'. What is going through that hose? Where is it going? The later systems went to the air cleaner base and had square mesh filter to stop the big stuff. That wouldbe better. But you still gotta ask yourself, ' what is that stuff going in my carb? expended gases? OIl? impurities? This aint a big deal. millions used with good effects. Keeps that stuff from going in the air. But does an engine make the same horsepower with straight gasoline or with gasoline mixed with "stuff"? Each person must make their decision as they see fit.

 

[jester]

Are the oil return passages clean ? All theese motors are plumbed in similiar way and yours is the first I have heard of. I wonder if there is an over abundent amount of oil remaining in the lifter galley from the extended higher RPM.
Just a thought .

 

[CHEV601234]

29,

You said you have your pcv mounted where the road draft tube would go. If that's true, you'd have a hose to the base of the carb or a fitting on the intake. If that hose is soft or swelled, the engine vacuum can be partially collasping it, and allowing the crankcase pressure to build, until it finally "burps" back out the filler neck. Mount the pcv on the carb base or a fitting on the intake, and route a new hose from an adaptor (where the road draft tube would mount) to the pcv.

As for what's going into your engine, if you have a street car, rather than a race car, the blah, blah, blah about pcvs is merely achedemic. It didn't help you solve your problem. Chevrolet provided millions of customers with cars fitted with pcv systems and they ran many trouble-free miles.

 

[29Coupe348]

i have a solid stainless steel line running fron the back of my carb, and like a 2" peice of hose to the pcv valve, its not soft or swelled....i dont understand what you are saying, you want me to mount the pcv directly to the carb???how the hell do i do that??????

 

[Ronnie Russell]

chev601234, You are exactly correct. "If you have a street car, rather than a race car"-- blah-balh-blah. I assume blah-blah-blah means performance is not an issue. The pcv system is the first mass=produced emissions control device mandated by the government. Millions of customers with cars fitted with pcv systems ran many trouble free miles. No argument about that, they had no choice. 29, I have no idea where your pcv valve is mounted. 60 is correct about its location. carb base or intake man. fitting that is pulling vacuum. Ive never seen one stuck in the back of an intake, but I havent seen a lot of things. That is why I suggest you use a road draft tube and see if you still throw out oil.

 

[threeimpalas]

Mike, "all gunked up in place you dont want it to ( ie; the underside of the car) ??? So you had rather force that "gunk" into the intake manifold? Im sorry guys, I give up. I guess I cant see the forrest for the trees. I will leave it alone, dont want to lose good friends because of a pcv valve.

Considering that his A is a fenderless street rod, and not a race car, I imagine that he'd rather not have the car be continuously covered in oil mist and the other crud said oil will attract to the underside of his show car.

In my case, the '59 SD is a "show car", uses a PCV valve, and can still roast the tires when the need arises. It performs flawlessly with no blow-by, no oil mist where it shouldn't be, and gets excellent gas mileage for the technology of the engine.

Given that a properly functioning PCV setup will still allow the engine to perform acceptably, I don't see why one would want to use a road draft tube in such a car.

 

[Ronnie Russell]

Mike, your 59 SD is a beautiful wagon. Did it come with a pcv valve? If not, I applaud you for adding one and helping to keep our air clean. Your quote of " Given that a properly functioning pcv setup will still allow the engine to perform acceptably etc." That is the differance between "show car guys and race car guys" Performance is never acceptable to us, we are always looking for more. A 74 Cadillac 4dr deville will roast the tires. As far poor old 29, seems he will oil the bottom of his show car or oil the windshield. At least with a road draft tube, he can see where he is going.

 

[mpris]

My 64 409/425 came with what is called a positive engine ventilation system (option K24). It has always been my understanding that this system does not have a PCV valve in the back of the front carb, but a PCV orifice of a fixed size. At the rear of the engine where the road draft tube would normally be, there is a metal pipe with a short rubber hose connected to the base of the air cleaner. Inside the air cleaner is a metal mesh filter to keep anything big from being sucked through the old road draft hole and also acts as a flame arrestor. The oil filler tube has a sealed cap and there is a 3/8 inch line from this filler tube to the oriface on the rear of the front carb. I do not believe there is a valve in this orifice to leak or stick. It is just a fixed diameter hole for vacuum. This system pulls clean air through the air filter to the rear of the engine, across the lifter valley and up through the oil filler tube, out of this tube into the rear of the carb and is reburned. If this is not how it works, I have been wrong for years. But it will not be the first thing I have been wrong about thats for sure. If I am wrong will someone please explain the actual way it works?
I do not believe a PCV valve will work efficiently on an open system (road draft) since you would have the air from the PCV portion of the system pulling unfiltered
dirty air up through the road draft tube, especially at at an idle. The shape at the end of the road draft tube at the end beneath the car is supposed to create a vacuum only while the car is moving. I would think you should use one or the other and not try to combine both.

Poocho

 

[jim_ss409]

I know that crankcase pressure causes horsepower losses, that's the reason racers use things like vacuum pumps, exhaust evacuator systems, and large breathers. I'd guess that the pcv system would cease to opperate at wide open throttle because there would be little or no vacuum. So I'd think at full throttle the system would work backwards blowing the pressure back out of filler tube and through the vented oil filler cap or the hose that goes to the air filter housing. I once had a car that would blow the oil cap off if you ran it hard. I looked at the cap on my 409 and I noticed that it only had two little holes ( about 3/8" ) that it actually breathed out of so I used a different cap that had a much bigger hole. Maybe the cap with the small holes would have been fine but I figured anything I could do to reduce crankcase pressure would be a good thing. I'd guess that the road draft tube system would have less crankcase pressure than the pcv system.

 

[Ronnie Russell]

jim , common sense--- I just love common sense!!!

 

[oldskydog]

Put in an air-oil separator like we use on airplane engines. I is a cannister about the size of an oil filter with a sort of screen mesh baffle inside. Any oil or crap coming from the crankcase is collected in the can and only vapor goes out.

 

[mpris]

Jim, a system with a closed PCV would not have a vented fill tube cap. Prior to 1964 I believe an open PCV system was used. Cheverolet went to the closed system in 64. In the system the fill tube cap is air tight and any pressure would take the same route as with full vacuum. That is, up the filler tube and out the hose to the back of the carburetor. At the point where the vacuum through the PCV valve is insufficient to create a clean air flow down through the air cleaner, the positive pressure in the system also forces the fumes up through the hose connected to the air cleaner into the top of the carburetor to be reburned. In either case the fumes would be reburned and nothing would be expelled into the air. The only problem I could see when this happens might be a little smoke out of the exhaust under high acceleration if the engine were blowing by a lot of oil. The secret to a properly working PCV system is for all the parts of it and the engine to be properly sealed. (No leaks around the PCV valve, no leaking valve cover gaskets, rear main seals, etc.) I think most all of the 64 409s came with the closed system and I never hear anyone complaining about them. I know mine has never given me any problems and it was raced quite a bit in 64-65.

Poocho

 

[29Coupe348]

well. what im gonna do for the rest of this season is, run a road draft tube, and run a hose out the rear of my car, and let the people behind me worry about it.

 

[Ronnie Russell]

29,, What ventillation system did your 348 leave the factory with? Whatever that system is ,,,,use it. It worked then, why wont it work today? If you throw oil out the back with the proper system, then your rings are worn out,,replace motor. Mpris,, Nodoubt your pcv system works great. It works exactly as the Federal Emissions Control Board demanded , to allow waste matter a route from crankcase to the intake system of the engine and into the combustion chamber to be burned and exited out the tailpipes. It works great!!! However, I am confused about the "clean air" you describe going in the rear of the engine , across the lifter valley and exiting out the filler tube hose and into the carb. Where does this clean air come from? The only clean or fresh air I know of is the air going into air cleaner , through the air filter and into carbs. How does clean air get under the intake manifold? The crankshaft spinning causes turbulance , and oil sling, along with crank impingeing at some times with oil causing a positive pressure in the crankcase.This pressure seeks the path of least resistance and will rise to seek a way out. Carb. openings have a negative pressure due to pistons intake stroke. Waste matter travels through rear vetillation tube from rear of intake manifold to base of air cleaner where it is sucked through filter into carbs to be burned in combustion chambers. Ventillation is aided by hose from oil filler tube nipple via hose to rear of front carb. Again, waste matter is sucked into carb base and into combustion chambers. System works great, exactly as it was designed. If I could clear up the mystery of the clean air moving across the lifter valley, then I would have a better understanding of the system .. Thanks for your time

 

[mpris]

Ronnie, the clean air comes into the air filter. It passes through the air filter and goes into and through the flame arrestor, which is inside the air cleaner. It then goes through the hose which is connected beneath the air cleaner to this pipe which is connected to the rear of the engine where the old road vent used to be. There is a vacuum on this line which is created by the system being closed and the oil filler pipe sealed and connected to the rear of the carburetor.
You can test this by removing the big rubber hose at the bottom of the air cleaner while the engine is running. There should be 2-3 inches of vacuum on this hose. This is what creates the continuous flow of clean air through the engine. This supposedly has a two fold benefit. It removes the blowby from the combustion process and reburns it and allows clean dry air into the engine to remove any moisture which may be present. In a normal engine, 70% of the blowby gases are made up of unburned fuel from the combustion process. So not a whole lot of the reburned material is oil.
The only time the blowby gases are brought back up through the rear of the engine and into the air cleaner is under extreme acceleration. This is the only time the vacuum at the base of the carb can be weak enough to be overcome by the crankcase pressure which may force the blowby back up through the rear of the engine into the air cleaner to be reburned. The closed system was designed to do exactly that under high loads.

Poocho

 

[Ronnie Russell]

Mpris, I asked for an explaination and that is exactly what I got. I wanted to learn and now I have learned, thanks to you. I would have not thought that there would be a negative source at that hose. With all due respect, I do believe the matter that is reburned is not as clean as you make it sound. There is much going on in the crankcase other than minimal blowby. That would be why many experience oily gunk near the road draft tube area. With the enclosed sealed system this does in fact burn that substance instead of spewing it. As I said earlier, the system works and works good, however I have not changed my mind as to what I wish going into my own combustion chambers. Those who are happy with their pcv systems, I am happy for them. I am also happy I do not use them. But again, thank you for your response, as I am always eager to learn.