Crankcase evacuation system on a Hemi

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  1. Moparjack 489

    Moparjack 489 FBBO Gold Member FBBO Gold Member

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    drives anyone a crankcase evacuation system with full exhaust system inkl mufflers ?
    it can be work , or can‘t ?
     
  2. LemonWedge

    LemonWedge Well-Known Member

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    Typically doesn’t work since there’s backpressure in the exhaust system. This backpressure could actually pressurize the crankcase, giving the exact opposite effect than what you’re looking for.
     
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    • Moparjack 489

      Moparjack 489 FBBO Gold Member FBBO Gold Member

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      Thanks for you’re answer !
       
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      • HEMI-ITIS

        HEMI-ITIS STREETER on LI FBBO Gold Member

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        Your better off with the breathers going to a catch can!
         
      • bearman

        bearman FBBO Gold Member FBBO Gold Member

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        Is that only for the hemi or others also.
         
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        • bearman

          bearman FBBO Gold Member FBBO Gold Member

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          Maybe I should ask does a mild 440 street engine need this.
           
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          • Moparjack 489

            Moparjack 489 FBBO Gold Member FBBO Gold Member

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            I think the evacuation system over the exhaust headers are an racing option for dragstrip‘s and so on . Just for a „ streetcar „ maybe not, because the most guys say it doesn’t work ‚d with a exhaust system inkl mufflers
             
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            • LemonWedge

              LemonWedge Well-Known Member

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              Evac systems really work best with low-tension oil-ring builds, which is common in drag race builds. Low tension rings can help free up some power, applying vacuum to the crankcase then helps those rings seal. The two components work well together. Just adding an evac system to a std tension ring build..... not sure if it would have much effect. I’m no expert, but I think I understand this correctly.
               
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              • HEMI-ITIS

                HEMI-ITIS STREETER on LI FBBO Gold Member

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                All crank cases must breath. How you do it depends on what you want and what you need.
                 
              • bearman

                bearman FBBO Gold Member FBBO Gold Member

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                just don't want a bunch of oil leaks etc,
                 
              • HEMI-ITIS

                HEMI-ITIS STREETER on LI FBBO Gold Member

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                What HP level ??
                 
              • bearman

                bearman FBBO Gold Member FBBO Gold Member

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                hemi its 500 hp with auto. its going to be a street driven car some track but mostly show and shine stuff.
                 
              • LemonWedge

                LemonWedge Well-Known Member

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                To help avoid oil leaks and keep the engine bay clean, I’d include a proper PCV system. I noticed when I went away from a PCV, and to breathers, my engine bay started getting dirtier. I’d like to add back the PCV, but since I now run an HP Holley with no manifold vacuum port, I’ll have to tap my manifold.... haven’t done it yet.
                 
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                • bearman

                  bearman FBBO Gold Member FBBO Gold Member

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                  i'm going to do some more research on this. i have zero power anything that might need vaccum but i do need the crank case to breath. i guess i can run the breathers into a one way check valve into the collectors on the headers. that should do it.
                   
                • HEMI-ITIS

                  HEMI-ITIS STREETER on LI FBBO Gold Member

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                  Pan evac s have their limitations.I also do not like PVc hose putting it back into the intake,,because if it does suck some oil it would be prone for detonation. Sooooo,if you don't care for the breather deal consider an electric vacume pump.
                   
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                  • weedburner

                    weedburner Member

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                    Not a Hemi, but for street/strip I use a hybrid system that uses both a pcv valve and an electric pump. A well designed header system only draws about 4-5" at full throttle with no exhaust restriction downstream. When idling around town, you won't get anything from it.

                    My journey started when I decided to try a Total Seal ADVANTAGE ring set. Basically it's a special low drag ring set that was designed for racing with engines that had to use stock width ring grooves. It uses groove spacers to allow narrower 1.2mm rings in the upper two grooves, combined with low tension 12lb oil rings. The low tension rings reduced effort to rotate the short block to 13ftlbs, which also netted a 325rpm gain at idle using the exact same carb/settings/calibration. Downside was with breathers only, this engine now went thru a qt of oil in about 250 miles. Since this was a street/strip engine, I decided to see if I could find a way to fix the oil consumption problem which would allow me to keep the rings. Here's my reasoning- Take two mostly identical engines, except one shortblock requires 40ft/lbs to roll over using regular oldschool piston rings, the other uses a modern low-tension ring pack and requires only 13ft/lbs to roll over. That's a constant savings of almost 8hp at 1500rpm. If your car cruises at 2500, that equals a constant savings of roughly 13hp worth of friction/heat/mpg while you are driving down the hiway. As a bonus, at WOT at 7000rpm the low-tension shortblock would have about 36 more hp on tap. Not to mention the reduced bore wear you get with low tension rings.

                    Here's my experience with electric pump only. At 12v they draw around 12 amps and 4-5"Hg of vacuum, but the pumps do not like to run constantly at full voltage. I added a voltage dropping resistor which made the pump much happier with constant duty, but then it only drew about 2-3"Hg. Still, that is great if all you are looking to do is eliminate oil leaks. Be warned the electric pump also makes a vacuum cleaner sound, which may be audible over the sound of an idling engine.

                    Next I got the idea to just use a pvc to draw vacuum for casual driving and turn on the electric pump only at WOT. This system turned out great for my street/strip car. Down the highway the pcv draws about 15"Hg with my 114 lca nitrous cam. In the end, the car gets about 20mpg in spite of 3.73 gears, 28" tires, and no overdrive. Been using the Advantage rings on the street since 2013, i'd estimate my setup uses a qt of oil in about 800mi. I never even turn the electric pump on unless i'm spraying.

                    Here's a graph tracking crankcase vacuum at WOT using pcv only, no electric pump at all. The 3rd gear pull starts at about 42mph/2500rpm and ends at about 101mph/6200rpm about 5.5sec later...

                    shopmulepcvonly.jpg

                    White line is crankcase vacuum, red line is engine rpm, blue line is WOT switch (nitrous was not armed). As you can see the crankcase still had about 4"Hg after about 5.5sec at full load.

                    Grant
                     
                    Last edited: Apr 26, 2019
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                    • HEMI-ITIS

                      HEMI-ITIS STREETER on LI FBBO Gold Member

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                      Do you use any sort of oil separator for the PVC? A vacume pump is on the bucket list after I get the tune right with a few different levels of boost.
                      Very interesting how you set that up.At WOT squeezin your using the PVC & VP.
                       
                    • weedburner

                      weedburner Member

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                      The pcv is actually located in the separator instead of a valve cover. Pcv doesn't really pull much at WOT by itself as manifold vac is really low, but there is so much crankcase volume that it takes a while for crankcase vacuum to drop. When I spray intake vac is even lower, so electric pump is there to make sure crankcase doesn't go positive pressure.

                      Grant
                       
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