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  1. #1

    Default Carb Valve Cover on a speed density EFI car

    Hi everyone. I’m trying to figure out if I can run a carb valve cover (85’ finned ‘Powered by Ford’ ones) on my 1986 Speed density EFI car. What concerns do I need to address and how do I replicate the (vacuum) setup of my stock valve covers on these carb ones?

    Thank you!


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  2. #2
    FEP Power Member richpet's Avatar
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    Unless I'm mistaken, don't you just have a pcv on one valve cover and an oil fill on the other? Or is the '86 different?

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  3. #3

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    Quote Originally Posted by richpet View Post
    Unless I'm mistaken, don't you just have a pcv on one valve cover and an oil fill on the other? Or is the '86 different?

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    Hi Rich, on the 86 the PCV is at the rear of the motor on the intake and one valve cover has an oil fill neck and the other is blank with no openings.


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  4. #4

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    There is no reason you cannot use them. You will need a flat non-breather cap for the drivers side, and use is closed breather cap on the other side and run a tube to the EFI intake. You actually could run a breather cap, and cap off the matching nipple on the intake tract, but they make a mess.

    Kenny

  5. #5

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    If you plan to retain the pcv system (closed system) in its oem functioning state,I'd suggest buying a closed breather cap that has a nipple on it so that you can retain the crankcase breather tube and place it in its oem location between the throttle body nipple and the closed breather cap nipple. The nipple on the passenger side valve cover is where the pcv valve pulls its fresh air source from during idle,deceleration & light cruise.This fresh air is sourced from the throttle body towards the valve cover.
    During wide open throttle,its vented from the valve cover towards the throttle body.
    Last edited by wbrockstar; 12-19-2020 at 07:57 PM.

  6. #6

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    Quote Originally Posted by mudgepondexpress View Post
    There is no reason you cannot use them. You will need a flat non-breather cap for the drivers side, and use is closed breather cap on the other side and run a tube to the EFI intake. You actually could run a breather cap, and cap off the matching nipple on the intake tract, but they make a mess.

    Kenny
    What do you happen to mean they make a mess?
    I found a Motorsport breather that I was going to use for the passenger side, and as you said I was just going to cap the nipple on the EFI. Would this work? Thanks!


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  7. #7

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    Quote Originally Posted by wbrockstar View Post
    If you plan to retain the pcv system (closed system) I suggest buying a closed breather cap that has a nipple on it so that you can retain the crankcase breather tube and run it between the nipple on the throttle body and the nipple on the breather cap.The nipple on the oem passenger side valve cover filler neck is where the pcv valve pulls its fresh air source from during idle, deceleration & light cruise.Its pulled from the throttle body towards the valve cover.
    During wide open throttle,air travels from the valve cover towards the throttle body.
    Oh so I need a closed one with a nipple! I couldn’t use a breather on the passenger side and just cap the nipple on the throttle body? Thanks


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  8. #8

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    Quote Originally Posted by marcod13 View Post
    Oh so I need a closed one with a nipple! I couldn’t use a breather on the passenger side and just cap the nipple on the throttle body? Thanks


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    Sure you can. Breather caps leak oil mist, that is the mess they make. The tube up to the intake tract sucks up and burns those vapors keeping less oil mist under the hood.

    There is someone selling closed with nipple, Ford Motorsports caps on ebay, they are fairly cheap.

    Lots of ways to skin this cat, it just matters what you want it to look like.

    Kenny

  9. #9

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    Quote Originally Posted by marcod13 View Post
    Oh so I need a closed one with a nipple! I couldn’t use a breather on the passenger side and just cap the nipple on the throttle body? Thanks


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    If you want the pcv system to function correctly & be efficient at evacuating the crankcase of corrosive vapors,keep the stock pcv system closed like it is in oem fashion.Running a straight breather(s) is a passive system that only equalizes the crankcase pressure,but doesn't evacuate the crankcase like positive crankcase evacuation does.Sometimes track only cars run breathers,but they usually have some way to make it into a positive system like a vacuum pump or connecting hoses to the headers in order to create the suction that the PCV valve does in our engine.Keep in mind too that the tube between the filler neck and throttle body is bi-directional.

    The following part number is a FRPP closed breather cap w/ nipple.


    #M-6766-D302
    Last edited by wbrockstar; 12-17-2020 at 11:02 PM.

  10. #10

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    Quote Originally Posted by wbrockstar View Post
    If you want the pcv system to function correctly & be efficient at evacuating the crankcase of corrosive vapors,keep the stock pcv system closed like it is in oem fashion.Running a straight breather(s) is a passive system that only equalizes the crankcase pressure,but doesn't evacuate the crankcase like positive crankcase evacuation does.Sometimes track only cars run breathers,but they usually have some way to make it into a positive system like a vacuum pump or connecting hoses to the headers in order to create the suction that the PCV valve does in our engine.Keep in mind too that the tube between the filler neck and throttle body is bi-directional.

    The following part number is a FRPP closed breather cap w/ nipple.


    #M-6766-D302
    Thanks for the info, I really appreciate it. I will go ahead and look for one with a nipple. In the mean time, would any damage be done to the car if it were ran with a regular ford breather without the nipple and the TB nipple closed off?
    Thanks!


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  11. #11

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    Quote Originally Posted by mudgepondexpress View Post
    Sure you can. Breather caps leak oil mist, that is the mess they make. The tube up to the intake tract sucks up and burns those vapors keeping less oil mist under the hood.

    There is someone selling closed with nipple, Ford Motorsports caps on ebay, they are fairly cheap.

    Lots of ways to skin this cat, it just matters what you want it to look like.

    Kenny
    In no way would this cause any damage to the engine? Happen to have the link to the closed cap?

    Thanks for the reply, appreciate it.


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  12. #12

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    Quote Originally Posted by marcod13 View Post
    In no way would this cause any damage to the engine? Happen to have the link to the closed cap?

    Thanks for the reply, appreciate it.


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    The following part # is for a closed breather cap with nipple.
    M-6766-D302

    On a maf equipped Foxbody,running a open breather cap with a closed pcv system will cause a lean condition as unmetered air is entering the system through the breather cap,since all air that enters the engine must be accounted for by the maf sensor.
    On a speed density Foxbody,running a open breather cap with a closed pcv system wont cause a lean condition since the pcv valve is a controlled leak accounted for in the ecu.However oil mist will likely be present at the breather cap location & surrounding areas.

  13. #13

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    Quote Originally Posted by wbrockstar View Post
    The following part # is for a closed breather cap with nipple.
    M-6766-D302

    On a maf equipped Foxbody,running a open breather cap with a closed pcv system will cause a lean condition as unmetered air is entering the system through the breather cap,since all air that enters the engine must be accounted for by the maf sensor.
    On a speed density Foxbody,running a open breather cap with a closed pcv system wont cause a lean condition since the pcv valve is a controlled leak accounted for in the ecu.However oil mist will likely be present at the breather cap location & surrounding areas.
    Thanks for the info!


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  14. #14

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    Quote Originally Posted by mudgepondexpress View Post
    There is no reason you cannot use them. You will need a flat non-breather cap for the drivers side, and use is closed breather cap on the other side and run a tube to the EFI intake. You actually could run a breather cap, and cap off the matching nipple on the intake tract, but they make a mess.

    Kenny
    Hi Kenny.

    Just to confirm.. the finned covers will clear the factory 1986 rockers, correct?


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  15. #15

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    Yes, they clear. Heck, with tiny modifications, they clear aluminum rollers.

  16. #16

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    Quote Originally Posted by mudgepondexpress View Post
    Yes, they clear. Heck, with tiny modifications, they clear aluminum rollers.
    Great to know!! For now I’m keeping with the factory rollers. What sorts of modification are necessary for aluminum rollers? Would I have to shave down the entire inside of the valve cover?


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  17. #17

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    You have to remove the baffles, shorten the legs in the cover, then reinstall the baffles. Mine have enough clearance for venting and filling with oil, but the filling takes longer due to the smaller clearance. It's been years but I seem to remember shortening the legs by half.

  18. #18

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    Quote Originally Posted by mudgepondexpress View Post
    You have to remove the baffles, shorten the legs in the cover, then reinstall the baffles. Mine have enough clearance for venting and filling with oil, but the filling takes longer due to the smaller clearance. It's been years but I seem to remember shortening the legs by half.
    Thanks very much!! Will give that a shot if the time comes!


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