ditching pcv for e-vac system - Hot Rod Forum : Hotrodders Bulletin Board
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Old 09-12-2002, 11:12 AM
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Post ditching pcv for e-vac system

Well the pcv valve is leaning out the carb to much and also I don't have enough vaccumm to run the thing properly so I'm putting on a Mr.Gasket crankcase evacutation system. Have any of you used this system? I heard all of the postitive things of this system but are there any negatives?

Charlie

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Old 09-12-2002, 12:54 PM
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I asked the same question a little while back. Everyone here seemed to think, the evc system only works at high rpms.An that for a street car i should stick with the pcv valve. I run a vaccum can for my brakes to have enough vaccum.This system came out on production Chevies for awhile. It would seem to me if they were used by and developed by Gm , they must have thought they were of some benifit. However. they quit putting them on there cars. Seems like i only saw them a few years. I know i used to take them off, when i got a car witht them. Although i don`t know why i did. This is a topic of intresat to me. Please let me know what you find out and decide to do.
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Old 09-13-2002, 03:51 AM
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Almost all cars have the vacuum cans ( although now most look like little plastic spheres, usually in multiples), they just stash them under fenderwells and such.They became fairly standard equipment when cars started using vacuum switching for heat/ac,etc. I have also seen air pumps used to build vacuum for brakes.
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Old 09-13-2002, 04:13 AM
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The pan evacuation system will not work properly with mufflers. The system was developed for use in race engines with low tension oil rings and does not function at low RPM. Mufflers, regardless of design will cause some backpressure, therefore the pan evacuation system will not work and may even be detrimental when the mufflers are operational. I think your engine has some internal problems that a band-aid is not going to fix.
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Old 09-13-2002, 05:12 AM
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Arrow

The PCV valve is also an air metering device, especially on emission engines. The orifice is of a fixed size for each engine type.

You need to buy the factory (Motorcraft-AC Delco) valve for your exact application.

Are there any other vacuum leaks?
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Old 09-13-2002, 08:35 AM
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Well the motor is not leaking oil anymore at all so the pcv valve has helped in that aspect, but I have been to the strip and a lot of the guys there are running a crankcase evacuation system to relieve the high crankcase pressure associated with high performance engines. As far as the mufflers go, I will check with the manufacture of the kit but I'm pretty sure there will be enough pressure coming from the exhaust to create a vaccum mufflers or not. This system also helps the rings seal better for better performance. I'll let you know how it works out.

Charlie
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Old 09-13-2002, 10:35 AM
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The pan evacuation system doesn't really make the rings seal better. It allows the use of very low tension oil rings, which don't do a very good job of controlling oil, but help reduce the friction drag caused by the rings. As you can imagine, piston rings are responsible for most of the friction losses in an engine and the oil ring actually develops more friction than both of the compression rings. There is also a lot of crankcase pressure caused by the pistons when they are travelling downwards on the power stroke. The evacuation system (that attaches to the header collector at one end and an oil seperator on the valve cover at the other end) works efficiently ONLY at high rpm (4500 and above) and will not work with any back pressure whatsoever from the mufflers. The NHRA Pro Stock and Competition Eliminator guys have gone one step further and use a pan evacuation PUMP. This pump is available from Moroso for about 400 bucks, as I recall. The pan evacuation pump can also be made from an old exhaust emissions air pump that came on GM cars back in the '70's. Hope this helps.

[ September 13, 2002: Message edited by: engineguy ]</p>
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Old 09-13-2002, 01:34 PM
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<a href="http://www.mrgasket.com/maildirect/helpdesk/problemdetail.asp?id=54038&TicketID=54038" target="_blank">http://www.mrgasket.com/maildirect/helpdesk/problemdetail.asp?id=54038&TicketID=54038</a> Hey dude, here is the link to what Mr. Gasket has to say about the crankcase evacuation system working with mufflers and at what rpm's it works at.

Charlie
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