Editing PCV system

==PCV valves for modified engines== Big cams with low idle vacuum throw can throw off a stock PCV valve, creating a lean idle. Normally at idle the PCV is in the low flow position. But if the PCV valve is open at idle (because of low idle manifold vacuum caused by a big cam), the idle gets lean and unstable and may suck too much oil along with too much air. This is akin to a big vacuum leak at idle because the PCV is open at idle instead of in the idle (low flow) position. ==PCV valve specs== *NAPA p/n 2-9229 (stamped 2088) GM 4/6/8 cylinder, '85-'95 **Spring free height is 0.775" **95 grams compressed 0.300" *NAPA p/n 2-9333 (stamped 2221) Ford 5.0L/460, '87-2002 **Spring free height is 0.800" **110 grams compressed 0.300" *NAPA p/n 2-9210 (stamped 2072, shown disassembled below) GM 262/350/454, '80s-'90s **Spring free height is 0.775" **117 grams compressed 0.300" '''NOTE:''' There are different pintel shapes and tapers. All the above have the same diameter holes in the internal "washer" that the pintle slides into. *Valve p/n 2221 and p/n 2072 use the same pintle with 4 cutouts in the large "nailhead" end and a short taper. *Valve p/n 2088 has a pintle that looks like a sawed off nail, no cutouts in the nailhead and a very gradual large diameter taper where it slides into the "washer". *All the above valves share the same 3/4" body diameter where they plug into the rubber grommet, and have the same plastic elbow pushed onto the top. Specs unknown at this time: *NAPA# 2-9230 (stamped V187) '80-'87 Chevette *NAPA# 2-9246 (stamped 2108) '74-'79 350/400/454 ==DIY adjustable PCV== The faster the air is flowing, the more likely it will carry oil along with it. So if your system uses a breather in the opposite valve cover, it might be a good idea to restrict it a little, to decrease the volume of air drawn into the PCV system. Using a larger diameter hose will further reduce the airspeed.<br> {{Note1}}This is conjecture at the present so until it's tried we won't know whether or not this will have an adverse effect on the function of the PCV system as a whole. Most PCV valves are very similar internally, just minor differences in the spring tension. You can customize a PCV valve fairly easily. Below is a common PCV valve for a SBC that's been cut open: [[File:Adj pcv1.jpg|250 px]] [[File:Pcv apart1.jpg|250 px]] [[File:Pcv apart2.jpg|250 px]] ==DIY catch can== *Catch can if used need at least a 3/8" connectors and baffles inside. Without some sort of baffle inside the catch can the engine will suck up some oil. The catch 'bottle' below is made from an air compressor oil separator. [[File:Pcv catch1.jpg|250px]] ==Fixed orifice PCV system== The LQ4 6.0L crate engine from GM comes with a fixed orifice in the valve cover. The paperwork says to throw the original PCV valve away and connect the hose to the nipple. It appears they are finding the correct size orifice for the engine vacuum and are no longer using a valve. Perhaps a small inline needle valve to adjust crankcase vacuum flow might be the ticket. Not too much to cause a major leak, just enough to evacuate the crankcase. ==High tech adjustable PCV== For those who can spend ~ $130.00 for an adjustable PCV valve, this might fit the bill: [http://mewagner.com/ M/E Wagner] [[File:M-E Wagner Cutaway-3-views.jpg|250 px]] [[File:M-E Wagner pcv1.jpg|250 px]] <br><br> [[Category:Engine]] [[Category:Undeveloped articles]] [[Category:Undeveloped Engine articles]]

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