Author Topic: PCV systems  (Read 234 times)

Offline stinger

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PCV systems
« on: July 06, 2018 - 11:03:10 pm »
was curious,are these simple stock breather/pcv systems up to the task on our modified hot rod engines that see spirited/racing type rpms or is it better to upgrade to something better and if so then what?




Offline 70chall440

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Re: PCV systems
« Reply #1 on: July 07, 2018 - 12:22:23 am »
Lots of variables to look at, I suggest you do some of your own research to arrive at an answer that you agree with. Bottom line is that an engine (any engine) needs to breath. Many race or HP motors use simple vents (breathers) to facilitate this where as others such as drag cars use scavenging systems. In the modern HP cars and tuners they use catch cans and run lines from each valve cover to them to catch the oil mist generated. There is some discussion that a PCV system was an attempt at recapturing some of the oil mist and reintroducing it to the engine where it can be burned off whereas the breather returned the mist into the air cleaner to be sucked back into the engine. Both of these were environmental based efforts by the manufacturers at the time. There is some argument around how this affected the performance of the engines of the time (both pro and con).

Should you run a standard PCV system, an open system or a captured system? All depends on what you want and are willing to deal with. A stock system generally is pretty maintenance free short of replacing the PCV valve from time to time and perhaps cleaning or replacing the breather. From a performance position, introducing oil mist back into the intake system is not desirable and can have a negative effect on performance. A open system (such as a small filter on each valve cover) works but can result in an oil mist on your engine and surrounding engine bay. A vented or catch system (where there is a line from each valve cover to a catch can) will work but has to be checked periodically and potentially emptied. Then there is another vacuum assisted system which in addition to the two lines adds a third line that is plumbed into a vacuum source; this creates positive pressure in the can and draws the oil mist into the can. they have a screen or filer to keep the oil out of the vacuum line. This too much be checked and emptied periodically. Lastly there is the scavenging system wherein there is a line that runs from each cover down to the headers (one line to one header), in this system the vacuum created by the exhaust pulls the oil mist into the collector where it is either burned or deposited under the car (and underneath the body). This system doesnt require much maintenance but isn't viable on a street car with full exhaust as the oil will accumulate in the exhaust and could cause some issues.

So there are your options, its up to you to decide what best fits your car/engine. On anything even remotely stock, I run a stock type system. If you are generating decent HP and want to experience all of it and dont mind wiping down the engine and bay once in a while, a open system will work. Want something more modern, a vented or catch system is for you.
Current Mopar
70 Challenger RT 440-6, 73 Cuda (under const)
05 Durango, 99 Dakota, 01 Ram 4x4, 14 2500 4X4, 10 PCP Challenger RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR, 61 Jeep FC170
Past Mopars
9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)

Offline stinger

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Re: PCV systems
« Reply #2 on: July 08, 2018 - 07:10:04 pm »
Thanks for the very informative reply! I was also thinking about built up crancase pressure that can cause blow by and oil leaks

Offline 70chall440

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Re: PCV systems
« Reply #3 on: July 08, 2018 - 08:57:37 pm »
Well technically that is what a breather system is for, to allow crankcase pressure to escape. The question is how and where it should escape. In the old days they just ran a pipe under the car and let it vent; some designs were more elaborate than others but basically they relied on the passing air during movement to create a low pressure area or even a vacuum to draw out the vapors/pressure. Of course this was determined to be not environmentally friendly not to mention having oil all over the bottom of the vehicle. It was at that point that PVC systems were developed which have evolved into in some cases very complex designs.

At the very basics of it, your engine needs to vent, how it vents and where is what you have to decide. Many modern cars especially HP ones pull a vacuum and there is some data that suggests this is beneficial to increasing HP. The issue then is what to do with the oil vapor which when it is accumulated is a volume of actual oil.
Current Mopar
70 Challenger RT 440-6, 73 Cuda (under const)
05 Durango, 99 Dakota, 01 Ram 4x4, 14 2500 4X4, 10 PCP Challenger RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR, 61 Jeep FC170
Past Mopars
9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)