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  1. #1
    FEP Power Member cjmuscle's Avatar
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    Default PCV or Breathers on the valve covers? Crankcase Pressure?

    Do I need the pcv valve that goes into the back of the intake if I am using breathers on the valve covers. Could that be what is causing me to have to much pressure in my crankcase?
    Chris
    --------------------------------------------
    1982 GT 347 Kenne Bell 2.2 Supercharged
    1986 GT VERT 306
    2002 GT VERT 4.6 Saleen supercharged (sold)
    1969 Mach I 427 Sideoiler Had 14yrs (sold)
    1968 Cougar GTE 427 Cover of Mustang Unlimited(sold)
    1968 Cougar GT390 (sold)

  2. #2

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    if you run a breather in both valve covers that is enough
    85 gt 347 stroker performance automatic aod
    79 cobra 302 4spd 37k original miles
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  3. #3
    FEP Power Member 81coupe's Avatar
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    if your running this once a week at the track, then open breathers would be fine. but however if this is a street car/ daily driver ect, then i would use a pcv valve.
    1981 Mustang Coupe: Rebuilt 91/306, Ported E7's, TF Spring kit, E-303 Cam, RPM Intake, Eddy 1406 Carb, FMS Dual Roller Timing set, March UD pulleys, Summit LT Headers, Summit 2-1/2" Chambered Mufflers w/ 2-1/2" FlowTech H-Pipe/ Flowtubes & 2-1/2" LMR SS Tailpipes. C4 trans with 8.8/ 2.73 Rear.

  4. #4

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    Breathers do not allow fresh air to purge the crankcase. An actual PCV system has a
    lot of benefits, and no real negatives. Don't confuse closed crankcase with PCV. You can
    have a functional PCV system using a breather on one valve cover, and the PCV valve in
    the other. Closed crankcase just means the fresh air comes from the air cleaner, rather
    than a breather.
    Cheers,
    Jeff Cook

    '85 GT Hatch, 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT Vert, CFI/AOD, all factory...
    '79 Fairmont StaWag, 5.0, 62K original miles ... '04 Azure Blue 40th Anny Mach 1, 37K original miles...
    2012 F150 S-Crew 4x4 5.0 "Blue Coyote"... 65 coupe, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ...
    '68 Vert, Mexican block 307 4-speed... '71 Datsun 510 ...
    And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune

  5. #5

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    Anyone still do road draft tubes? thats what i am thinking of using on my 82. Input?
    No Longer a 4I Owner
    But Have way too much 4I stuff Collecting Dust.

  6. #6
    FEP Power Member Ourobos's Avatar
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    Is this fuel injected or carb'd?

    On a fuel injected car, you either run PCV as Ford set it up, or run NO PCV, and run breathers. On forced induction, it's best to always just run breathers, to keep from blowing seals out. The problem with fuel injection and running a breather AND a PCV is that you're pulling unmetered air in through the valve cover, so the ECU is getting inaccurate readings.
    1986 CHP SSP Coupe

  7. #7
    FEP Power Member cjmuscle's Avatar
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    It is fuel injected and has a Kenne Bell Supercharger. Right now it has two breathers one on each valve cover and the pcv on the back of the intake. If I eliminate the pcv on the back of the intake will that get rid of the crank case pressure.
    Chris
    --------------------------------------------
    1982 GT 347 Kenne Bell 2.2 Supercharged
    1986 GT VERT 306
    2002 GT VERT 4.6 Saleen supercharged (sold)
    1969 Mach I 427 Sideoiler Had 14yrs (sold)
    1968 Cougar GTE 427 Cover of Mustang Unlimited(sold)
    1968 Cougar GT390 (sold)

  8. #8
    FEP Power Member Ourobos's Avatar
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    Quote Originally Posted by cjmuscle View Post
    It is fuel injected and has a Kenne Bell Supercharger. Right now it has two breathers one on each valve cover and the pcv on the back of the intake. If I eliminate the pcv on the back of the intake will that get rid of the crank case pressure.
    Yes, that is exactly what I did on my s-trimmed 336, and it makes over 500hp with ZERO issues.
    1986 CHP SSP Coupe

  9. #9

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    Chris, I just made the swap from 2 breather elements, and swapped out a pcv valve on the right side valve cover. After the 2 breather elements continually got soaked in oil, and taking some advise from Jeff Cook in another thread about the pcv, I swapped out to a pcv valve, and I no longer have the breather getting soaked in oil. Fresh air drawn in through the breather, and pulled through the intake and out the tailpipe. Let me know if you need a hand.
    79 Capri RS
    341 rwhp,348 rwtq 11.20@127


    1939 Pontiac Deluxe 6. 73,xxx original miles. Barn find. Currently the secomd owner.

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  10. #10
    FEP Member Bailey28's Avatar
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    You have to be very careful on what type of valve covers you are using as far as the PCV system goes. I have had problems with oil being sucked right into the intake on my car after installing a good PCV system.

    The first time, I used aluminum valve covers with a metal plate baffle installed 3"x3" around the breather/PCV hole. I used a PV98C valve hooked to the 3/8" port on the carburetor base. I also used a breather on the other valve cover. I thought it worked great until......

    I had a smoke issue when starting, running, or just getting on the gas. I took off the carb and the entire intake inside was filled with dirty brown oily goo.

    On the second build I just completed, I went with a pair of Moroso baffled vavle covers, and a genuine Motorcraft PV98C. I thought I would have better oil control. I was wrong. The new engine ran great, although within a few hours of run time, the whole intake AGAIN was coated in brown dirty oily goo. And is smoked on start up!!

    I even at one point tried an in line air to oil separator on the PCV line, and it started filling with oil within a week, as well as the intake plenum again arrg!!

    I cleaned out the intake and ran a breather with the 3/8" hose nipple on the end. It is a Moroso breather, like the ones you would use for an exhaust evac system. I did not use a PCV valve with this breather, it is a closed breather that plugs directly into the valve cover. I then routed the 3/8" hose to a brass nipple port I installed in the air cleaner base inboard of the air filter. I still ran the open breather on the other vavle cover.

    Basically I got the air cleaner to act as the suction instead of the carb base plate port which is less suction, however there still is some suction.

    I've driven the car for the past three weeks now, and guess what? No more smoke, AND after pulling the carb to check on the condition of the intake plenum, NO MORE OILY GOO!! The entire intake plenum and all runners are spotlessly clean and bone dry.

    I'm not discounting a proper PCV system and believe that it is needed for cleaner engine operation etc. However, all of the systems I tried up until this last one without the PCV valve have not worked well. Maybe the vapors have been sucked in well, but along with the vapors came oil!!

    If anyone has any tips for us on how NOT to suck oil through your PCV valve hooked to manifold/baseplate vacuum, I'd love to hear it.
    Last edited by Bailey28; 04-17-2010 at 08:16 AM.

  11. #11

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    Quote Originally Posted by Bailey28 View Post
    You have to be very careful on what type of valve covers you are using as far as the PCV system goes. I have had problems with oil being sucked right into the intake on my car after installing a good PCV system...

    If anyone has any tips for us on how NOT to suck oil through your PCV valve hooked to manifold/baseplate vacuum, I'd love to hear it.
    Well, first, -all- PCV systems suck in some oil. But it should not be enough to cause visible
    smoke. Have you done a leakdown test? Are you running a high-volume oil pump? It sounds
    like you're trying to re-engineer the crankcase ventilation system, when the real problem is
    excessive blow-by, or your oiling system is packing too much oil up in the valve covers...

    The valve covers are actually not the best place to put a PCV valve, they're just usually the
    most convenient. And most aftermarket valve cover baffles leave much to be desired. Better
    than nothing, but they seldom exercise the same care in design and construction as the OEMs
    do. There's a -lot- of oil splash going on in there. Especially if you're using a high-volume oil
    pump...

    The back of the intake manifold is actually a much better place, and is where the factories
    often used to place the separator can for their road-draft setups. Not all intakes have the
    open real estate to put a PCV tube, but it's something to think about. Just don't forget the
    separator element.

    I have also used the older Ford oil cap stand-tubes to hold a separator element, along with
    the push-on cap and an inline PCV valve. Unfortunately, most aftermarket valve covers use
    the cheap Chebby style push-in grommets. (I really hate those.)

    Quote Originally Posted by theemustangman View Post
    Anyone still do road draft tubes? thats what i am thinking of using on my 82. Input?
    A road draft tube is a poor substitute for a PCV system, even if you do it correctly, which
    most don't. In theory, the slash-cut end of the road-draft tube is supposed to pull air
    through the crankcase when the car is moving. But it can only do that if it's constructed
    properly, and is placed in an area under the car that gets proper airflow. And you would
    still need baffling or a separator, else the underside of your car ends up coated in oil.

    A better solution would be to use angled slash-cut tubes welded into the header collectors,
    with air pump system anti-backfire valves. Or a crankcase evacuation pump.

    Quote Originally Posted by Ourobos View Post
    Is this fuel injected or carb'd?

    On a fuel injected car, you either run PCV as Ford set it up, or run NO PCV, and run breathers. On forced induction, it's best to always just run breathers, to keep from blowing seals out. The problem with fuel injection and running a breather AND a PCV is that you're pulling unmetered air in through the valve cover, so the ECU is getting inaccurate readings.
    This is important for a mass-airflow car, but does not matter on a speed-density car, since
    the airflow is not metered.

    As for keeping the PCV system from pressurizing the crankcase when you're using forced
    induction, I might suggest doing how at least some factory systems do it. Use a PCV valve
    that seals under pressure, such as one for a Thunderbird SC. Then route both valve cover
    openings to the the intake tract ahead of the blower. Extra points if you place a slash-cut
    tube in the inlet pipe (oriented properly of course).

    I wouldn't let examples of laziness or bad engineering dictate what's best.
    Cheers,
    Jeff Cook

    '85 GT Hatch, 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT Vert, CFI/AOD, all factory...
    '79 Fairmont StaWag, 5.0, 62K original miles ... '04 Azure Blue 40th Anny Mach 1, 37K original miles...
    2012 F150 S-Crew 4x4 5.0 "Blue Coyote"... 65 coupe, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ...
    '68 Vert, Mexican block 307 4-speed... '71 Datsun 510 ...
    And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune

  12. #12
    FEP Member Bailey28's Avatar
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    Thanks for the reply, I don't think I am trying to re-engineer the system, I just set it up like most everyone else here. I used the chebby style rubber 5/8" grommet in one valve cover with a PCV valve, and an open breather in the other. Then I plugged the 3/8" hose into the big 3/8" port on the base of the carb.

    Then I have oil in the intake issues.

    I have no doubt that I am pulling the oil through the PCV system as eliminating the standard system and going to the air cleaner breather with no PCV valve has cured the oil in the intake for me.

    The engine is the new rebuilt one I bought from a local rebuilder with a good reputation. I noticed the oil after a few hours on a brand new build however I changed it to the current system I have now with no issues. Yes, I prefer to run a PCV in the valve cover, as there is nowhere else to tap into unless I want to drill and tap a hole in the manifold behind the carb. I haven't noticed really any smoke running the engine with no breathers in either cover in the driveway after the build, whereas the other engine would puff smoke out of both covers like hot steam.

    I agree the Moroso covers probably are not the most efficient at blocking the oil splash up to the PCV. I also bought a standard volume standard pressure Ford brand factory aluminum oil pump as well. Stock oil pan, 5 qts. in the car with an FL1A.

    I am using Comp roller lifters aftermarket, which have an even smaller oil feed hole to the pushrod cup than the stock Ford lifters I took out.

    I wouldn't mind trying a set of stock finned 83-85 valve covers if I knew they would clear the Harland Sharp 1.6 roller rockers i have.

    I know on the earlier cars with the finned covers there is a yellow cap that the PCV plugs into.. Is there an oil separator in there? Mabye plugging the PCV directly into the cover is too much exposure to the oil and vapor activity which is my issue...

    Let me know how they are set up, so I can go back to using the correct seperator and the PCV in the valve cover with better luck.
    Last edited by Bailey28; 04-17-2010 at 02:01 PM.

  13. #13
    FEP Member Bailey28's Avatar
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    I just came from Autozone a few minutes ago, and saw an oil separator breather cap that had a fine silver screen type mesh with a white pad in it. I'm not sure what car it went to, but it had a 5/8" tube on the bottom for a grommet type install,, and a 5/8" hole in the top on an angle for another grommet type hose to plug into.

    This is similar to the set up I have now, however I only have black cell foam in my breather, not the fine screen type thing.

    Is this what I need? I doubt the factory yellow PCV mount would fit the covers I have now as the factory covers have the larger hole with the cutouts at 9 and 3 O'clock for a twist on type mount.

  14. #14
    FEP Super Member 86capriASC's Avatar
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    Meanpony, the first issue I see with the older style VC's is that your throttle cable bracket will hit the oil cap and or breather.
    Mike

    1986 ASCMclaren #108
    stock short block, Victor EFI, 75mm TB, 3.08's, Borla cat-back, slot style MAF conversion, Gt-40p heads, TFS1 cam, 80lb injectors, 69mm turbo, Moates Quaterhorse, E85. 501/584 @ the rear wheels

  15. #15

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    Quote Originally Posted by 86capriASC View Post
    Meanpony, the first issue I see with the older style VC's is that your throttle cable bracket will hit the oil cap and or breather.
    hmm yeah i havent had it back together yet since i took the upper intake off so its very possible. If thats the case Ill just put the stock ones back on if its gonna cause me problems because i just wanna drive the thing.

    Quote Originally Posted by Ourobos View Post
    You can buy the trick flow press in oil filler neck, with a nipple on it that runs to the nipple on the throttle body, thus keeping the factory method the Ford engineers designed.
    Thanks. Good to know. Sounds like what i had in mind in the first place but couldnt find.
    own:
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    previously owned:
    1978 Mustang II hatchback,t-top, auto, 302
    1985 Mustang GT hatchback, auto, t-top
    1986 Mustang GT hatchback, 5-spd, hardtop
    1986 Mustang GT convertible 5-spd (#1)
    1993 Mustang GT convertible 5-spd triple black
    1998 Mustang GT hardtop, auto

  16. #16
    FEP Member Bailey28's Avatar
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    This is what I am using now on the left valve cover. I plumbed it right to the inboard side of the air cleaner base.

    This is what the Moroso catalog says:

    No. 68781 is ideal for plumbing your crankcase ventilation system into the air cleaner, Uses internal foam disc and baffling to prevent oil from entering air cleaner ,68781* Replacement Oil Separator/Breather. Chrome. For street use only
    Attached Images Attached Images  

  17. #17
    FEP Power Member Ourobos's Avatar
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    You can buy the trick flow press in oil filler neck, with a nipple on it that runs to the nipple on the throttle body, thus keeping the factory method the Ford engineers designed.
    1986 CHP SSP Coupe

  18. #18
    FEP Power Member Ourobos's Avatar
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    1986 CHP SSP Coupe

  19. #19

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    Quote Originally Posted by Ourobos View Post
    Thats perfect, except it would be way in the way more then the FR breather.

    Hmm would it be possible to put that on the drivers side valve cover instead, or is the pcv vacuum designed strictly for the stock setup left/passenger valve cover ?

    that would allieviate my throttle cable clearance issue
    own:
    1986 Mustang GT convertible 5-spd (#2)

    previously owned:
    1978 Mustang II hatchback,t-top, auto, 302
    1985 Mustang GT hatchback, auto, t-top
    1986 Mustang GT hatchback, 5-spd, hardtop
    1986 Mustang GT convertible 5-spd (#1)
    1993 Mustang GT convertible 5-spd triple black
    1998 Mustang GT hardtop, auto

  20. #20

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    This is a great thread...I am facing this exact situation on my new motor (tall valve covers not meant for EFI use), and still unsure as to which way to go with the PCV system...keep us posted

    Quote Originally Posted by MeanponyGT View Post
    Thats perfect, except it would be way in the way more then the FR breather.

    Hmm would it be possible to put that on the drivers side valve cover instead, or is the pcv vacuum designed strictly for the stock setup left/passenger valve cover ?

    that would allieviate my throttle cable clearance issue
    MC makes a throttle cable bracket that might be of some help, check it out:

    http://mc-machine.com/mcm_joom/content/view/23/36/
    1986 Capri RS w/ FRPP Z347BOSS crate

    2011 F-150 SCREW ecoBoost FX4

  21. #21
    FEP Power Member Ourobos's Avatar
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    Doesn't matter which side they're on, but you'd have a hose running from the filler neck over to the throttle body.
    1986 CHP SSP Coupe

  22. #22
    FEP Power Member cjmuscle's Avatar
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    Ok just ordered a Moroso 3 vane vacuum pump to eliminate the crank case pressure. My tuner told me that my rings wont seat properly and am losing power if I don't install a vacuum pump system.
    Chris
    --------------------------------------------
    1982 GT 347 Kenne Bell 2.2 Supercharged
    1986 GT VERT 306
    2002 GT VERT 4.6 Saleen supercharged (sold)
    1969 Mach I 427 Sideoiler Had 14yrs (sold)
    1968 Cougar GTE 427 Cover of Mustang Unlimited(sold)
    1968 Cougar GT390 (sold)

  23. #23
    FEP Power Member David Claflin's Avatar
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    If you're using an open breather with a PCV on an EFI system, be advised you're drawing air into the engine that is not being metered by the mass air meter which could lead to lean fuel stumble or other issues that contribute to poor operation.
    1985 LTD LX, Mach1 brakes, 17" Mopar police car wheels. 302, T5, 4.10s
    1984 LTD station wagon, with 84GT nose, some might remember it as the old Dugan Racing station wagon.
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    1990 Red LX, ported AFR heads, TFS-R box upper, weenie cam, 1 3/4 long accufabs, 3" exhaust, T5, 4.56

  24. #24
    FEP Power Member Ourobos's Avatar
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    True, see post # 6.. LOL
    1986 CHP SSP Coupe

  25. #25

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    Quote Originally Posted by David Claflin View Post
    If you're using an open breather with a PCV on an EFI system, be advised you're drawing air into the engine that is not being metered by the mass air meter which could lead to lean fuel stumble or other issues that contribute to poor operation.
    Quote Originally Posted by Ourobos View Post
    True, see post # 6.. LOL
    You guys must have missed the part where I mentioned that I am plugging the drivers side valve cover. The other valve cover I plan on tying into the TB for vaccuum. I am aware of unwanted, unmetered air and it's affects on the ECU...just wondering if he had noticeable amounts of oil pulled through his intake. I should also mention that I am running a tall valve cover c/w baffles. Again, no PCV here and no breathers either.
    1986 Capri RS w/ FRPP Z347BOSS crate

    2011 F-150 SCREW ecoBoost FX4

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