AMC Eagle Den Forum
The Mighty 258 => Emissions/Vacuum Systems => Topic started by: ammachine390 on January 02, 2012, 08:56:56 PM
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My 258 always seemed to have too much blowby, it would blow the oily fumes into the air cleaner. This would cause the air filter to get all oily and dirty, and eventually there would be oil puddles in the air cleaner. One solution is to use the Envalve, but that costs $58. My solution was to take the normal pcv valve, and cut the very bottom of it off, and remove the valve components on the inside. This keeps a constant vacuum on the crankcase. I then took an and old air injection check valve and put it on the breather line so that the crankcase holds the vacuum, but if there is a time when the vacuum drops too low, it will still be able to vent the pressure. So far it's been working, the air filter has been staying clean, and my acceleration has improved. Also, thanks to JayRamb who provided with some answers about his experience with the envalve.
Here's a pic of the check valve setup.
(http://i815.photobucket.com/albums/zz79/ammachine390/amcpcv.jpg)
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Interesting - good idea - and such. What was Jayramb's prognosis of the N-valve ??I had been considering one. Now I wonder if I have a air system check valve around.......... thanks.
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AFAIK, JayRamb was very satisfied with the Envalve. I think the check valve might be leaking some vacuum, but it's very minimal (almost like a regular pcv valve would pull fresh air in) but I might take it off and see it how it works without the valve and just have the system totally sealed. When the crankcase is totally sealed, and the engine is idling pulling about 21 inches of vacuum, the crankcase would hold a steady 8 inches, even while accelerating the engine. I never got the crankcase close to presurized, so I think the check valve may be unnecessary, I put it on as a "just in case" while testing. So far, it looks like it has never had to vent.
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Nice alternative cheap solution! I run two pcv valves in my I6's (er, well, ok, in Eaglegirls 258, and my 4.0, lol), hers and mine had some excess pressure too, some problem has ceased.
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Here's a pic of how I cut the pcv valve to allow constant flow.
(http://i815.photobucket.com/albums/zz79/ammachine390/amcpcv2.jpg)
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UPDATE:
The check valve does not appear to leak any vacuum, so the crankcase in completely sealed.
Drove the car on the highway at speeds 65 mph and higher for about an hour. Engine was always above 2000 rpm, and I don't think the crankcase ever had to vent excess pressure as the air filter was completely clean. Gas mileage was a little higher than 20.3 mpg.
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Whats an envalve and why is it $58
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Whats an envalve and why is it $58
http://www.envalve.com/
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So I don't get it it still does exactly what a pcv does now......doesn't it?
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A properly working PCV system should allow a small amount of vacuum to the crankcase, so that it pulls in just a very small amount of fresh air through the breather tube.
My car had more blowby than the PCV system could handle. Instead of fresh air being drawn in through the breather tube, oily blowby gasses were being pushed out, which would make the air filter all oily and dirty very quickly, and sometimes there would be puddles of oil in the air cleaner. This seems to be a common problem on a lot of 258s.
My solution puts the crankcase under constant vacuum. I closed off the breather hose by putting the check valve in, so no fresh air enters the crankcase anymore. If the line were left open, it would cause a large vacuum leak.
Jeep 4.0s used a system called CCV, where they used a metering orifice in a a vacuum elbow to put vacuum on the crankcase, however, the CCV system, has a breather hose that is always open to the atmosphere.
In the end, all 3 do the same thing, just differently. They are all used to pull blowby vapors from the crankcase.
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I ended up going for a slightly different solution to allow vacuuming off any positive pressure from blowby that otherwise would have built up.
- For fresh air, a separate air filter that fits in the front valve cover hole. Immediately, extreme blowby can't build up as it would escape out this filter. Any oil from extreme blowby would foul this air filter, not your carb air filter.
(I'd prefer some sort of clear line going to the air cleaner so I can see if there's blowby oil getting into it, with an upside-down goose-neck to keep that oil out of the air cleaner. But I haven't gone looking for that yet.) - To pull air out, instead of a PVC valve at the front, a plastic elbow at the rear, #47057, that has a hugely reduced hole to limit vacuum pull. So no PVC valve that can get stuck.
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I did the same thing. Worked pretty good. (apparently never changed the oil, it smelled burnt and was black when I first changed it). I definitely have a fair amount of blow by. The filter breather I placed at the front gets quite oily and when driving at freeway speed I get oil running down the valve cover from it. Not sure yet what I will do about what I hunk is excessive wear. 🤔
Will figure it out when I pull the Head!
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Been reading what you have done to get the PCV working well. I am sorting thru my very stock Eagle 258 now. I had a bad valve cover leak, common problem, and in the process of removing the valve cover have started to go thru the emissions system. There is a switch with a "T" connected to the vacuum hose from the front PCV and then the "t" connection goes to the carb. I am thinking that I should just eliminate the switch and go straight to the carb. But what else is linked to that electrical switch? Then there is the rear PCV that goes to the air cleaner. Why not just put an oil breather on that? I don't have oily air cleaner so blow by not an issue. I did find the PCV hose leading to the switch was kinked closed so it could not have done much and maybe caused the pressure to build up enough to make a failing valve cover gasket leak worse. Suggestions please.
Charlie D
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That "switch" may be the original PCV solenoid. It was there to shut off the PCV flow at idle. AMC had a recall that did away with that solenoid and replaced the hose with one that had an orifice in it. Maybe your car never had the recall performed on it!
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Thanks! Very interesting. I get to complete a 34 year old recall! So if I dead head that solenoid connection, there are no other electrical consequences, right?
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There should be no other electrical issues. However, be sure to secure the solenoid connector away from contact with the body and engine as it's electrically "hot" at all times. Originally, the engine computer grounded the solenoid to actuate it. :eagle: