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Discussion Starter #1
Got a question about the pcv system on a 66 mustang...

First - Was pokin around and found a mechanism found on the valvecovers that my buddy said was a PCV valve, but he didn't know what it was for, just what it was called. It was on the driver side valve-covers toward the rear. Whats it for?

Second - If I'm using aftermarket valvecovers with no provision for a PCV valve, are there going to be problems? Was this just for smog control? I wanna valve covers and just stick a breather on it..this gonna work?

Thanks for any help ya can give,
Chris
 

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The PCV allows us to vent the crank case and send the "polluted" air that is built up in the crank case through the cylinders to be burned up ... It's just about that simple.

As you will read in the link ... I'm not crazy about them, especially in a car that does not have to excecute against "Smog Laws".

My opinion is ... As long as you have free flowing ventelation of the crank case ... you should be just fine without it.
 

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Thanks for the link...That answered most of it. Gonna mess around with it and see what happens. I remember my old shop teacher had a rail dragster that had his valvecovers vented straight into his exhaust system..I remember seeing this setup for sale in the jegs catalog (called the "positive locking breather"..needed for cars running 7.77 sec in 1/4 m. blah blah..) with the note it's intended for drag use...not that I would set this up on my car, but why is it for drag cars? Why is there that restriction about cars running 7.77 sec having it? Does the exhaust flow create too much of a vacumn on the engine for a street engine? Thanks

Chris

<font size=-1>[ This Message was edited by: srfmustang on 3/21/02 12:28pm ]</font>
 

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Your car will run better and make more power if you have a negative vacume in the crank case, the drag race only application you spoke about was actually suggested for my car by a very respectable Ford and Mustang mechanic since I drag my car a lot and had a problem of oil being exspunged from my breather tube. The deal is at wide open throttle there is no manifold vacume so crank case pressures are not being relieved, with the drag race method a bung is welded in to your exhaust and the hose that would go to the manifold vacume source is routed to the bung in the exhaust which gives more vacume to clean out the crankcase as the rpm`s go up. If I am not mistaken you will burn oil if you dont have some sort of crankcase relief, because the pressure from blow by will build up and make its way past the rings bringing some oil with it as I understand the process, but I may be wrong.
 

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Your both right. The PCV (Positive Crankcase Ventilation) is a very needed piece. Sure, it looks like sh*t sometime when it leaks but it principal funtion is to help relief the pressures in the block. If you find your blowing a lot of valvecover gaskets, this could be a reason also. venting the pressure out the headers is the best method for high compression / competition engines. The "bung" welded into the collector is actually a one-way valve, only allowing the pressure to flow out and no exhaust pressure to blow in. This valve actually sucks the fumes out of the case because of the vacuum generated by the exhaust thus making POWER ( we all like that).
Anyways, that is what I have learned in the last 27 years and my Canadian nickle's worth. (US 2 cents)
 

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If you look through catalogs like CV Products, Moroso, Canton etc, you will find the crankcase evacuation setup described above. The two bungs welded into the headers have the ends cut at an angle, and a whistle like notch taken out as well. This causes a pretty strong vacuum signal at higher rpm's. There are also two anti backfire valves (good use for an "evil" emissions part) that act essentially as a one way valve. This is run by mostly sportsman class racers on a budget. The hot setup is a vacuum pump, which is a a good 'ol air pump off any late 70's / 80's car. The pros run this setup to pull some impressive vacuum numbers in the crankcase for improved ring seal and more HP. Dry sump systems also frequently have a scavenge section that is used only to pull a vacuum in the crankcase. As far as I'm concerned, I always use a PCV valve. I've never seen a reason not too, and I don't consider it an emissions part, but a valuable piece of my setup that keeps my engine cleaner.
 
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