FYI FORD - MustangSteve's Ford Mustang Forum
The Internet's Most Knowledgeable Classic Mustang Information
IF YOU HAVE A QUESTION ABOUT CLASSIC FORD MUSTANGS, YOU HAVE COME TO THE RIGHT PLACE!
MustangSteve has over 30 years of Mustang experience, having owned 30 of them and restored several others. With the help of other Mustangers, this site is dedicated to helping anyone wanting to restore or modify their Mustang.... THERE ARE NO DUMB QUESTIONS!!!!!
Visit MustangSteve's web site to view some of my work and find details for:
FYIFORD Contributors' PICTURES - Power Brake Retrofit Kits for 65-66 Stangs - Classic Mustang FAQ's by MustangSteve - How to wire in a Duraspark Ignition - Mustang Ride Height Pictures and Descriptions - Steel Bushings to fit Granada Spindles to Mustang Tie Rods - Visit my EBAY store MustangSteve Performance - How to Install Granada Disc Brakes MustangSteve's Disc Brake Swap Page - FYIFORD Acronyms for guide to all the acronyms used on this page - FYIFORD Important information and upcoming events

You are not logged in. Would you like to login or register?

  • Index
  •  » FYI Ford, Classic Mustang Tech Discussion
  •  » Excessive blow-by

    • 1 of 1

       

    12/19/2018 6:33 AM  #1

    daily driver
    FYI Addict

    Offline

    Registered: 1/02/2018
    Posts: 125

    Excessive blow-by

    289, 4100 Autolite. Bored .30. Are there different levels of pollution control valves which stay open at higher speeds in unless vacuum?

    Last edited by daily driver (12/19/2018 6:38 AM)

     

    12/20/2018 6:07 AM  #2

    TKOPerformance
    Hyper FYIFORD ADDICT

    Offline

    From: Newark, DE
    Registered: 12/15/2014
    Posts: 7,526

    Re: Excessive blow-by

    There are supposed to be different PCV valves for different applications, but good luck finding one today.  Every replacement I've seen in the last 20 years is basically a universal replacement.  There are aftermarket PCVs which are adjustable.  I put a group buy together for them a year or so back.  They aen't cheap, but they work really well.  ME Wagner is the company, located here:

    http://mewagner.com/

     

    12/20/2018 7:55 AM  #3

    daily driver
    FYI Addict

    Offline

    Registered: 1/02/2018
    Posts: 125

    Re: Excessive blow-by

    Thanks TKO.
    Reving it up in netural, I still have good vacuum at higher rpms. Seems like plenty of vacuum to significantly reduce crank case pressure. It's hard to tell without being under a load. Does vacuume reduce, at 70 mph, or become greater?
    Actually it's as if this motor likes to run 1 quart low! Or they put a high pressure oil pump  in. I don't have the factory hose coming from oil filler cap to the air breather. Oil cap is stock vent and there is a little oil on valve cover there once in a hot-rod while. What do you think would happen if I put a oil filler cap with PCV valve in it and Teed it in the other PCV at the back of Edelbrock torker 289 manifold? Do you think this would create a vacuum leak I'd have to compensate for? Or counter the first PCV?
    Thanks for your help.

       •Thread Starter
     

    12/20/2018 7:57 AM  #4

    Huskinhano
    FYI Addict

    Offline

    Registered: 4/26/2017
    Posts: 279

    Re: Excessive blow-by

    daily driver wrote:

    289, 4100 Autolite. Bored .30. Are there different levels of pollution control valves which stay open at higher speeds in unless vacuum?

    That’s why they went from a open PCV system to a closed PVC system in 68. The open system uses the regular vented cap for fresh air into the crank case. But as you see the problem is at low manifold vacuum it doesn’t work very well and let’s the crank case fumes, blow by, to escape out the cap. The closed system stops this. Now under low manifold vacuum the fumes get captured in the air filter assembly and drawn into the carburetor. Under normal loads the air filter assembly supplies fresh, filtered air to the crank case.

    I'm not a complete idiot.....pieces are missing. Tom
     

    12/20/2018 10:12 AM  #5

    TKOPerformance
    Hyper FYIFORD ADDICT

    Offline

    From: Newark, DE
    Registered: 12/15/2014
    Posts: 7,526

    Re: Excessive blow-by

    Vacuum is always best at idle.  Vacuum has to be built against something, in this case its the throttle blades.  Once those blades start to open vacuum decreases.  So, at 70MPH with the blades cracked, even under a light cruise (RPM obviously is going to be dependent upon rear gear ratio, tire size, and type of transmission) there's going to be less vacuum at 70MPH than at idle. 

    I wouldn't run two PCV valves.  The spring that operates the valve needs to be overcome by crankcase pressure, and I'm not sure what having to overcome twice as much spring pressure would do.  If it delayed PCV opening you'd get oil pushing out past seals, etc.  Messy at best. 

     

    12/20/2018 5:38 PM  #6

    daily driver
    FYI Addict

    Offline

    Registered: 1/02/2018
    Posts: 125

    Re: Excessive blow-by

    Thanks guys. My breather is original but cut out all the way around (no sidewalls). I tried what I think Tom calls a closed system with an oil filler cap and hose mounted inside the air filter area next to the carburetor. But that's not really closed without the sidewalls. I believe it help a little.

       •Thread Starter
     

    12/21/2018 12:38 PM  #7

    whlnut
    I FYI 24-7

    Offline

    From: Brunswick, GA
    Registered: 4/02/2013
    Posts: 317

    Re: Excessive blow-by

    Check the torque on the intake manifold bolts. They can loosen and allow the gaskets to the head fail. Felpro makes a SBF gasket set that can seal better with a steel core.
    1250S-3. Re-torque a couple times after driving if you do replace. Same as header bolts.

     

    12/21/2018 3:10 PM  #8

    TKOPerformance
    Hyper FYIFORD ADDICT

    Offline

    From: Newark, DE
    Registered: 12/15/2014
    Posts: 7,526

    Re: Excessive blow-by

    I used Mahle gaskets when I installed my intake.  They look exactly like the Victor ones that were on the car.  I had a hard time finding a gasket that was right for pre '78 heads.  The water passages on the '78-up gaskets are wrong. 

    I'd advise coating the gaskets in Permatex Aviation Gasket Sealer.  It never fully hardens, so even if a leak develops you can just retorque the bolts and problem solved. 

     

    12/23/2018 7:23 PM  #9

    MS
    Forum Originator

    Offline

    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 12,300

    Re: Excessive blow-by

    Do your valve covers have the original baffles inside?  If removed, oil mist gets sucked directly into the intake manifold and burned whenever the PCV valve opens.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    12/24/2018 2:00 AM  #10

    351MooseStang
    FYI FORD Member

    Offline

    From: Brookings, Oregon
    Registered: 4/03/2013
    Posts: 91

    Re: Excessive blow-by

    A properly sized PCV valve is restricted at idle and open at cruise. At idle the vacuum overcomes the internal spring and pulls the internal valve towards the vacuum inlet, restricting flow from the crankcase. Crankcase flow increases when the engine vacuum has dropped low enough for the internal spring to push the internal valve off of the vacuum inlet port, removing the restriction. That spring and the amount of restricted flow (the internal valve) are what made up a recommended PCV valve. Now we get universals or buy the spendy custom.

    A closed PCV system works best on a V engine with the PCV mounted in one valve cover and a vent hose running from the other valve cover to filtered air within the air cleaner. I have an Edelbrock Pro Flo on my 351W and I solved the vent hose problem by throwing away the tiny plastic barb they include and replacing it with a 1/2" NPT connection w/ 3/4" line from the valve cover to the bottom of the Pro Flo. Inside the Pro Flo I used a gas grill gas tube to route the vent line inside the air cleaner to dump directly into the primaries on the carb. Since I'm using M/T valve covers and roller rockers, that means no baffles so I did some other mods to the valve covers to assure that I'll never have to suffer valve cover related leaks ever again.

    I hate leaks! Good luck with solving your problem!!
     

    Last edited by 351MooseStang (12/24/2018 2:03 AM)

     

     

    1 of 1

  • Index
  •  » FYI Ford, Classic Mustang Tech Discussion
  •  »  Excessive blow-by

    • Board footera


    REMEMBER!!! When posting a question about your Mustang or other Ford on this forum, BE SURE to tell us what it is, what year, engine, etc so we have enough information to go on.