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Thread: T1 PCV valve function

  1. #1
    Supporting Member Turbo Mopar Contributor
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    T1 PCV valve function

    I don't fully understand the function of my T1 PCV valve, please advise.
    1)a large diameter tube runs from the valve cover to air box, most excess crankcase gas will flow via this route.
    2)on the above tube is where the PCV valve sits. So when the valve sticks or pcv valve gets twisted sideways this allows air to get past the PCV valve shutoff and flow into the intake manifold via a tube connected to the intake compressor housing. And as expected the engine idle increases to 2,000 RPM. The issue of the tilting PCV valve has increased in frequency since I changed from an older 87 Valve cover to a new one piece gasket design. Yes I have several new and used PCV valves

    So why did the engineers do this? I am unclear why unless a federal regulation states that the car must have a PCV valve in this configuration. I am planing to block the PCV valve to scroll flow.
    Thoughts/comments?
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

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    Supporting Member Turbo Mopar Contributor supercrackerbox's Avatar
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    Re: T1 PCV valve function

    No, it was never a great design, but it was federally mandated sometime in the early '70s and this seemed to meet the regulations. The basic idea is that the vapors created by the heated and spinning oil and any combustion gasses that get past the rings will be vented by the PCV system and routed back into the intake stream where they will be (somewhat) re-burned and sent back out the exhaust to the catalytic converter.

    As for your twisting/sealing issue, it kinda sounds like your hoses may be too short. I don't see why going from an '87 valve cover to an '89-up would change anything as they should have both used the same vent. Unless of course you have the really old log intake setup which would have a long 90° vent tube on the valve cover instead of the short straight one on the later cars. I'd have to see some pictures to offer ideas.

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    Re: T1 PCV valve function

    The permanent fix for this is to add a second tube in the valve cover for the PCV valve, use a short 90 degree elbow to mount the PCV valve straight up and then run the hose to the vacuum port on the intake manifold.

    Or you can use a TBI cover that already has the second tube, and run the PCV valve hoses as above.

  4. #4
    Supporting Member Turbo Mopar Contributor
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    Re: T1 PCV valve function

    re supercrackerbox---Yes my 87' cover had a long 90. Once my CSX is on the road the Sundance will be upgraded to Tii with two piece manifold etc, etc. So short term I was thinking of plugging the PCV

    re crusty shadow----I am planning to switch to a TII configuration as my permanent fix. I do have several TBI covers on my shelf but I like the look of the Turbo ones.
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

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    Re: T1 PCV valve function

    Quote Originally Posted by chromguy View Post
    re supercrackerbox---Yes my 87' cover had a long 90. Once my CSX is on the road the Sundance will be upgraded to Tii with two piece manifold etc, etc. So short term I was thinking of plugging the PCV

    re crusty shadow----I am planning to switch to a TII configuration as my permanent fix. I do have several TBI covers on my shelf but I like the look of the Turbo ones.

    Cut the extra tube off a TBI cover, drill an appropriate hole in the turbo cover, take it to a welding shop and have the tube welded to the turbo cover. This also gives you an excuse to strip and repaint your turbo cover so it looks all nice and new again.

  6. #6
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    Re: T1 PCV valve function

    I use a TBI cover; I found out if I don't keep my crankcase in vacuum, my car would burn oil. PCV system is what provide the vacuum for my car. When my car is in boost, the PCV is shut and crankcase pressure exit out the other port.

  7. #7
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    Re: T1 PCV valve function

    the rubber piece , the 3 way that the pvc mounts to , which one are you useing since the valve cover swap ?
    if it's the old log motor one I could see it giving you trouble with the straight nipple on the newer valve cover

    the TI /TII ones are different - the end the tube to the air box fits into is angled downwards instead of being straight like the log motor's

    onerippinturbo2 used to have a bunch for sale (nos) so they are still out there - I'd start with him if looking for one

    also , the ends of the pvc tubeing often had squeeze clamps to hold it together - but not all cars it seems

    I probably have a decient used pvc 3 way TII style thingy if you need one

    agreed it could have been a beter system
    the combined pcv vent / fresh air vent is just a bad design - especially considering the downhill tube to the air vent in the air cleaner box

    I've wanted to modify it for a long time with two of the elbows off a log valve cover, one twisted 90* up comeing out of the valve cover and one 90* to turn it parrallel to the engine again
    I think the upturn straight out the back of the valve cover might help a lot
    - a vertical wall and gravity might help knock some suspended oil out of the crankcase vapors right at the valve cover

    the fail with the pvc system is mopar clung to the old design of putting the mandated enclosed fresh air crankcase vent in the aircleaner - like on an old v8 where the air cleaner is above the valve cover on the carb , thus the vent is uphill - and the pvc is usually on the opposite valve cover or opposite end of , so there's no cross contamination

    adding an open element fresh air filter should fail a visual smog parts inspection but if a box were put around it and a hose off the box run to the air cleaner at some point it should pass ok

  8. #8
    Supporting Member II Turbo Mopar Contributor ajakeski's Avatar
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    Re: T1 PCV valve function

    TII and later TI style PCV grommet is still available fro Mopar. (PN 4387568). I just order some.

    4387568
    Hose-Crankcase Vent Valve
    $8.07




  9. #9
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    Re: T1 PCV valve function

    Thanks Guys!
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  10. #10
    Supporting Member Turbo Mopar Contributor 2.216VTurbo's Avatar
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    Re: T1 PCV valve function

    Minor hijack here Chromguy but it is PCV related The PCV system on RedBox has been giving me trouble since day one. When Cordes drove it from SDAC last year to Cali(well to PHX actually) he was adding a liter of oil every time he filled up the tank. The build was barely completed hours before SDAC began so there was no shake down time to check out how everything worked. During SDAC the motor smoked some but not too bad, as the meet progressed and it got more miles the smoking got worse and worse. So one afternoon at JT's house a few of us pulled the valve cover and had a look. That's when we found that the #3 exhaust valve guide was dropping into the head and the valve seal was doing nothing but riding up and down on the valve stem. I assumed that's where the oil smoke was coming from and why Cordes had to add so much oil on the journey west. He even oil fouled a plug on the trip and had to change it BUUUT it was on the #1 cylinder At the time I didn't think to much of that and kinda just parked RedBox for a couple months when it got here as I knew I'd have to pull the head to fix it. I decided just to build a new head for it so I spent 30 hours porting a good swirl core, ordered +1 valves, comp cams springs(the ones that Todd N. reccomends) and had the cylinder head guys I use put all new guides in, back cut the valves, open the seats etc. I wanted to have the new head built and ready to install before pulling the old one off. Upon teardown I found a TON of oil in the #1 intake runner, like a puddle! At the time I was still thinking the #3 exhaust guide was the oil burning culprit so that was a head scratcher but it jived with Cordes having to change that plug on the trip. There was so much burnt/coked oil in the #1 runner of the TU header that I had to use a porting cartridge roll to clean it out. Still thinking the oil burning problem was something in the 'old' head I proceeded with the swap, got the new head on and fired the motor. It STILL smoked! (BTW when the head was off I inspected the cylinder walls and piston crowns closely, everything looked good so I didn't pull the pistons, now I wish I had) My brother noticed while it was running that there was a sucking or vacuum leak sound. Couldn't find any open hoses or obvious leak sources but then he pinched off the vacuum source that goes from the TII intake nipple to the PCV valve. THe sound stopped and the idle went down, clearly it was moving A LOT of vacuum thru there. Then it occurred to me, that vacuum nipple is directly over the #1 intake runner. All this time, at SDAC and on the trip to Cali, it was pulling oil out of the valve cover barb into the intake manifold and burning it in the #1 cylinder.

    So now to try and fix it. First I replaced the PCV valve with a new Mopar one, still had a massive amount of vacuum moving thru there. Then I tried restricting the vacuum source from that 3/8"s nipple down to a very small orifice. Still smokes, still sounds like a vacuum leak. Then I tried an all metal Supra turbo valve that Tryingbe put up a link for in another thread. Nice valve but it still didn't stop the smoking, Then I tried blocking off that vacuum source all together and just running a barb from a couple inches in front of the compressor wheel of the turbo to the other side of the PCV three way T. Still smokes. That's about where I'm at now. Under constant throttle like cruise condition the smoke goes away. Under heavy throttle and in boost the smoke goes away as well(I was thinking bad turbo seal but it should INCREASE in smoke under boost if that's the cause?) When the smoke is the worst is while idling at a light for anything more than 45 seconds, then it gives me a huge embarrassing puff when I take off. Not sue what to try next or even if the PCV system is whats causing the smoke? Any ideas?

    AJ (no More Alan) 84 Rampage RT TIII/568 Quaife 87 GLHS dealer optioned Red 16V Masi/568/Quaife
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  11. #11
    Supporting Member II Turbo Mopar Contributor ajakeski's Avatar
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    Re: T1 PCV valve function

    Alan, is the oil baffle inside the valvecover sealed on all of the internal ribs?

    http://www.badassperformance.com/mtech/valvecover.html

    You may want to add a TBI oil baffle under the valve cover as well. I had oil pouring out of the valve cover PCV port of the van. I resealed the baffle and trimmed a TBI baffle to fit in there as well. I also went with a later model mopar PCV valve that is a bit tighter.
    No more oil vapor issues.

  12. #12
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    Re: T1 PCV valve function

    Quote Originally Posted by 2.216VTurbo View Post
    Minor hijack here Chromguy
    Wow, hijack away...mine is an inconvenience at most, open the hood give the PCV valve a push, and I am good for another month. By far, your issue is more important to solve!
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  13. #13
    Supporting Member Turbo Mopar Contributor 2.216VTurbo's Avatar
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    Re: T1 PCV valve function

    Quote Originally Posted by ajakeski View Post
    Alan, is the oil baffle inside the valvecover sealed on all of the internal ribs?

    http://www.badassperformance.com/mtech/valvecover.html

    You may want to add a TBI oil baffle under the valve cover as well. I had oil pouring out of the valve cover PCV port of the van. I resealed the baffle and trimmed a TBI baffle to fit in there as well. I also went with a later model mopar PCV valve that is a bit tighter.
    No more oil vapor issues.
    Thanks Miles

    Not only did I pull it apart, spend 30 minutes cleaning and scraping off the old RTV and carefully resealing it, I built another small baffle that covers 75% of the factory gaping hole in the 'entrance window' to the baffle. That didn't help.

    The Supra valve is great under boost, closes instantly(mouth test lol) but under suction it still draws a fair amount. I *had thought* PCV valves were off(boost) on (light vacuum) off (heavy vacuum) valves? That's why that internal weight moves up and down in there under varying condtions right?. NO ONE valve I tested (probably 6 total of new ones and auto parts store shelf) closes off vey much under vacuum. So if that's the 'norm' then there is always a vacuum leak in the intake manifold nipple?? On RedBox its enough to raise the idle even with the Supra valve AND a new factory Mopar PCV valve.

    AJ (no More Alan) 84 Rampage RT TIII/568 Quaife 87 GLHS dealer optioned Red 16V Masi/568/Quaife
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    2014 Explorer DD'r 3.5Twin Turbo Ecoboost AWD and 500HP
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  14. #14
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    Re: T1 PCV valve function

    how a PCV works from Wikipedia

    The PCV valve is a variable orifice that controls the flow of crankcase fumes, admixed with fresh air admitted to the crankcase by the breather, into the intake tract. With no manifold vacuum, a restrictor—generally a cone or ball—is held by a light spring in a position exposing the full size of the valve's orifice to the intake manifold. With the engine running, the restrictor is drawn towards the orifice by manifold vacuum, restricting the opening proportionate to the level of engine vacuum vs. spring tension. At idle, manifold vacuum is high, but a large amount of extra air would amount to a vacuum leak, causing the engine to run too lean and/or too fast. So at high manifold vacuum, the PCV valve allows only a low flow rate. This is in accordance with the low volume of crankcase fumes generated at low engine speeds. At higher engine speeds, with less manifold vacuum, the PCV valve permits a greater flow rate to keep up with the greater volume of crankcase fumes; because of the higher engine speed, a greater amount of "extra" air via the PCV system can be tolerated without upsetting the engine's running. At full throttle, very little manifold vacuum is present, so there is little flow through the PCV valve. However, this is the condition under which the maximum volume of crankcase gas is present. Most of it escapes under its own pressure via the crankcase breather, flowing into the engine's intake tract via the air cleaner.
    A second function of the PCV valve is to protect the engine in case of a backfire, which causes a sudden high-pressure pulse in the intake manifold. This forces the PCV valve closed so that the backfire flame can't reach the crankcase, where it could ignite flammable fumes and cause damage. turbocharged engines also experience periods of high intake manifold pressure during which the PCV valve is closed and the crankcase fumes are admitted to the engine via the breather and air cleaner.
    Some engines use a fixed orifice rather than a variable-orifice PCV valve
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

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    Re: T1 PCV valve function

    Chrom,
    When you went to a 1 piece gasket VC did you swap The tubes coming out of the VC? The only way the engine idle should increase is if you have a vac leak betweeen the PCV valve and the intake manifold, Maybe a zip tie on those connections would help.

    Alan,
    What angle is the motor sitting back at? Stock is 12 degrees. The more the motor sits back the more oil puddles in the back of the head right next to the bottom drain ports of the baffle (course you want to make sure you don't rtv those up). All the oil drains in the head are at the front.

  16. #16
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    Re: T1 PCV valve function

    Quote Originally Posted by GLHNSLHT2 View Post
    Chrom,
    When you went to a 1 piece gasket VC did you swap The tubes coming out of the VC? The only way the engine idle should increase is if you have a vac leak betweeen the PCV valve and the intake manifold, Maybe a zip tie on those connections would help.
    No I did not swap tubes as my Tll stuff is in storage and I was busy selling my 1975 H1 (which sold to a guy in the UK). My thread was to help me understand why our PCV system are designed as they are and why. The good news is I now have a better better ideas, thanks to everyone's input. I will fix the issue when things settle down a bit.
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  17. #17
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    Re: T1 PCV valve function

    The PCV valve is a metered vacuum leak, it's not supposed to close off completely.

    Did you follow the instructions in the factory TSB about resealing the baffle in the valve cover?

  18. #18
    Supporting Member Turbo Mopar Contributor 2.216VTurbo's Avatar
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    Re: T1 PCV valve function

    Quote Originally Posted by crusty shadow View Post
    The PCV valve is a metered vacuum leak, it's not supposed to close off completely.

    Did you follow the instructions in the factory TSB about resealing the baffle in the valve cover?

    More good suggestions guys, I'll check the angle of the Motor Jay but I did spend considerable time on the drainback holes on this head, getting all the obstructive casting flash out and contouring the drainbacks so oil wouldn't puddle in the head. I do get your point about the angle, those drain holes are in the front.

    I didn't follow any TSB Crusty but I did seal it carefully and ensured that the two drain areas are left open.

    So the Wiki explanation did essentially say what I thought the PVC valves on a turbo motor did. Three positions. Off, on a little, and off(mostly) My thinking still is though if the valve allows enough flow under vacuum at idle to RAISE the idle, it's too much. Right?

    Drove RedBox a few miles today, pretty much the same. Little puff at start up then clears up under cruise and boost, then when the motor is fully warm the real smoke starts, heavy decell causes smoke and so does extended idle at stoplights. Three plugs are clean but #1 shows oil burning on it.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    AJ (no More Alan) 84 Rampage RT TIII/568 Quaife 87 GLHS dealer optioned Red 16V Masi/568/Quaife
    90 Masi 16V White/Ginger/Black
    89 TC Masi 16V Red/Ginger/Black
    86 GLHS #110 RoadRace Built 89 CSX-VNT Recaro Car
    89 Turbo Mini 'Woody' 85 GLHT 'RedBox'
    2014 Explorer DD'r 3.5Twin Turbo Ecoboost AWD and 500HP
    My profile page has over 20,000 views, I'm somebody LOL

  19. #19
    Supporting Member Turbo Mopar Contributor supercrackerbox's Avatar
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    Re: T1 PCV valve function

    I'd check your valve seals and do a compression or leak down test, Alan.

  20. #20
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    Re: T1 PCV valve function

    Quote Originally Posted by supercrackerbox View Post
    I'd check your valve seals and do a compression or leak down test, Alan.
    i agree with this, with everything you say you've done it could be excessive blow-by getting past the rings and pressurizing the crank case and forcing oil past the pcv valve.
    disconnect the pcv valve from the intake, plug the vacuum line and run a hose from the pcv valve over to a temporary catch can like a soda bottle (make sure to have a vent hole in the top of the bottle or the cap ) and drive the car. if you're still getting lots of smoke or see oil in the catch can after a drive then its rings or valve seals. no smoke and little to no oil in the catch can and its the pcv system not working correctly.

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