Latest attempt to stop oil through the PCV valve

[mlowry1260]

I gave up and put 3 K&N breathers on it and eliminated the pcv entirely. The guys who run Big Shot Dyno said the pcv probably hurt my power some last Saturday. At WOT when the pcv cannot evacuate enough fumes, the overflow goes right back into the air inlet tract. This contaminates the intake charge, lowers the compression ratio and can cause detonation. That makes sense to me.

The oil actually lowers the effective octane of the fuel mixture, not compression.

You may need to check the tune if it's rich. Ask your tuner. The stock eec-iv calibration actually accounts for some airflow through the pcv system.

[wick]

At WOT when the pcv cannot evacuate enough fumes, the overflow goes right back into the air inlet tract. This contaminates the intake charge, lowers the compression ratio and can cause detonation. That makes sense to me.

Oil does not take compression. Thats impossible!!!! It robs octane.

[94Cobra]

I meant to say octane rating. The car was rich on the 1st dyno run, but we adjusted fuel pressure and I believe A/F was 13 on the last runs.

[Rodeheaver's]

these are other people opinions...
Hey Big Block,
The only time to not use PCV is on an all out race only car.In a drag car most of its use is at wide open throttle (WOT),there fore no vacuum.Although in this case header scavenger kits should be used because they create vacuum at WOT to act as PCV.

The PCV has many advantages; it collects the crank case smoke-smell and burns it through the engine,also as the engine warms up each time you run it,there is condensate formed inside the crank case,the reason to run 180 thermostat or hotter is to turn this condensate into steam and also draw it through the PCV - engine and burn it,other wise sludge occurs quicker. The biggie I like is the engine leaks much less oil when system is evacuated properly.

The last thing is even with large cams the vacuum rises every time you lift the throttle making the PCV function, mabe not as well as stock cam,but unhook it and see how much oil it starts leaking.

Larry
The goal of the PCV (Positive Crankcase Ventilation) system is to simply relieve the pressures which build up in the cylinder head due to pressurization of the crankcase. You see, as the piston is pumping up and down in its respective cylinder, you might think that the only pressure it's creating is that due to the compression of the intake mixture. You'd be incorrect. You also have to take into account the compression occurring on the back side of the piston on the downward stroke. This, plus the small blowby past the piston rings (or large amount if your rings are shot) lets gases enter the crank case area where your crankshaft is pumping away. Since the head is joined to the crankcase via the oil return ports, the cam galleys would become pressurized as well if no purging system existed. If the engine was a closed system, this pressure would build up and would eventually start rupturing seals and blowing oil all over the place. That's where the role of the PCV system comes in.

[Rodeheaver's]

It is one pollution control device that serves a good purpose. As mentione in above posts, they are designed to proactively keep crank case pressure at a minimum, reducing pollution of your oil. A minor but worthwhile benefit is that it takes unburned hydrocarbons form the crank case and puts them back through the engine. Probably improves your gas mileage by 0.00001 mpg! seriously, it is a good thing to have on your engine.

I installed a new 600cfm carb and a PCV first on the right side then was told it should be on the left, heaven knows why, but i did. The car hasn't pushed a drop of oil since! P Postitive C Crankcase V Ventilation........run it off the PCV port of your carb. A very small price to pay for a solid running and free breathing engine.

our turbos PCV [COLOR=blue! important][FONT=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif][COLOR=blue! important][FONT=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif]systems[/FONT][/FONT][/COLOR][/COLOR] are identical to the NA engines with the addition of an additional line typically going to the airbox which will allow some vacuum to be sent to the VC during boosted operation

there is no need to eliminate it and actually if you do, it will likely create problems for you; its not primarily an emissions issue - it will also help reduce oil leakage, and if you have excessive ring blowby (which is not uncommon on TD's ) it will eliminate issues like the dipstick popping out and blowing oil all over your engine compart

[Rodeheaver's]

there are good reasons to run a PCV system, and no real reason not to

even 'all out' drag cars run it, and they certainly wouldnt unless there was a good reason...

"Dragsters use a scavenger system and venturi tube in the exhaust to draw out combustion gases and maintain a small amount of vacuum in the crankcase to prevent oil leaks on to the [COLOR=blue! important][FONT=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif][COLOR=blue! important][FONT=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif]race [/FONT][COLOR=blue! important][FONT=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif]track[/FONT][/COLOR][/FONT][/COLOR][/COLOR]."I removed the pcv valve that was running to the carb.

Now after running the engine I notice fumes/smoke coming out the oil breather caps

[94Cobra]

Great information Tim - thanks for sharing. I really wanted to keep the pcv, but I was getting too much oil into my overflow bottle and grew tired of emptying it. I thought real hard about pulling the lower and fabricating a baffle to cover the entire underside of the lower. However, I found some people that said that did not even correct their oil control problems. I do get some white steam through all 3 breathers, but no oil so far. I have been monitoring my seals and a known oil leak on my valve cover grommet that is unused. The leak has not become any worse with the breathers than it was with the pcv. I feel at WOT, which my car sees quite a bit , the breathers would be more effective than a single, small pcv valve. I could be wrong on that and have no way of knowing for sure.

[wick]

I still cant figure why people say not to run one. I have never seen a reputable engine builder not do this unless in a full on drag situation. Its the most sensless thing ever stated!!! I have however seen seperators in-line with them to catch most of the oil "mist" that may come out. Research negative pressure on a crank case and see whats said. It speaks for itself.

[Wolfpack Speed]

copy and paste what ever you like, call it sensless...i really don't care!!! im not talking out my a$$, im speaking from experience!!! like i tell people all the time, situation dictates and there are certainly pros and cons to this but some of this is just straight up amusing. just putting my 2 cents in, not sure why i waste my time anymore...unsubscribing

[Rodeheaver's]

Please dont get me wrong, i am putting up info for 94Cobra to read and understand that some people like Ford,GM, Honda,Toyota,Isuzu,Dodge,chrylser,daywoo, believe that it is important to have some positive crankcase ventilation, youi know so the rings and other related parts last longer than 10-15k miles... Or you know he could just let the pressure build and let the rings flutter and seals blow out.. I'm not arguing, so please don't anybody go off the deep end with this one.. And please keep in mind that the only name i have mentioned is 94Cobra's, and he and i are just about completely like minded on the matter, but he is having problems (13 trys) getting to this goal... SO please, everyone have a great day!!!

[Killercanary]

94cobra- one thing that you may want to look into is the the metal plate under the holley intake. It has more of a "gap" between it and the intake itself than any other aftermarket intake that I have seen. When I just had my lower intake ported I beat the edges of that baffle down even closer to the lower intake to help reduce the amount of oil getting by the metal baffle. there is still plenty of room for vapors/pressure to escape past, but its not the big gap that it was before. I plan to disconnect the PCV all together and get two breathers (one on each VC) and run them into a catch can when I put my new heads on, I've seen nothing over the years that would prevent me from doing so. I "may" even look into fabing up a 99 cobra crankcase evac. pump down the line and run the breathers into that. Pulling vacuum on the crankcase isn't a bad thing as long as its not too much, but sucking oil into the intake tract is a bad thing too.

[94Cobra]

I don't think their is a right or wrong answer on this subject - it is all a matter of what works for each unique situation and accepting the tradeoffs. I have talked to several machine shop owners - it is about 50/50 on running a pcv or breathers. Fox Lake told me to take off the pcv crap and throw it as far away from my car as I could. My engine builder told me to run a pcv if I can avoid the oil control issues. He also said that 80% of his engines he builds just run 2 breathers with no problems. He used to build engines for a professional racing team and he has his opinion just like everyone else. I would rather change my oil more frequently using breathers than continue to draw oil into my intake tract with the pcv. I think if I pulled my intake to fabricate a baffle and still had the issue, I would be really pissed off about it. I don't have any more patience for this problem. Now if I blow out my rear main seal, then I will probably wish I pulled the intake.

[94Cobra]

One issue that I noticed that the breathers seem to have solved. When I used to run a pcv, I would notice a slight whistling sound from the engine every morning on the same stretch of road when I was in second gear and manifold vacuum was very high during engine braking. Well, with the breathers, that whistling is gone completely. Some have told me the whistling was due to my BBK throttle body. However, I still have the TB and the whistle is gone. During one of my 13 attempts to keep the pcv last year, I rerouted the vacuum lines on the pcv and heard the very same whistle that I just eliminated with the breathers. I'm not certain, but I think that whistle was caused by inadequate crankcase evac due to the restricted factory pcv setup. I am just posting up my first-hand information here in case others can benefit from it.