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75 Imperial valve cover gasket question

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  • 75 Imperial valve cover gasket question

    My 75 Imperial (440-4) 4-DOOR has a VACUUMN LEAK. I've traced it to one of the valve covers so I suspect gasket. Went to Autoz Zone to get one and they have 2 different kinds---one "regular" and one "heavy duty high performance". They look different. Which one do I need? How can I tell without removing the valve cover? (I don't want to remove the cover until I have the time to put in the new gasket--my mechanic life tends to work like this--if the job takes the average guy 20 minutes, it takes me 4 hours!).
    "Semper ubi sub ubi"

  • #2
    Either will work. They're the saw size but different materials. I'd go with the cork one for a street car that might have the valve cover remove on nice every ten years
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    • #3
      Come on now guys a valve cover ain't gunna have a vacuumn leak! Oil maybe but not vacuumn. It is probably the intake where the vacuumn leak is at. The intake is a little more involved in removing and replacing!

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      • #4
        You are probably seeing your pcv line in the valve cover. Maybe stuck?
        It probably isn't a bad idea to change out the valve cover gaskets. (especially if you are seeing oil smoke when you shut down) I had cork on a couple of mine and it worked well. It is good for about 10 years.
        If you haven't changed your vacuum lines, they should probably done anyway. Make sure you get some new Ts and fittings too when you buy the line.
        If it is the intake, it isn't too bad to pull off. Just be sure to clean things before you remove it to limit the crap into the ports. It could be a rusty valley pan in the sealing area. It might be a good time to drop a Performer on there. (I don't think an RPM will clear the hood)
        The nine most terrifying words in the English language are, 'I'm from the government and I'm here to help.'
        Ronald Reagan

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        • #5
          Originally posted by tdzik
          My 75 Imperial (440-4) 4-DOOR has a VACUUMN LEAK. I've traced it to one of the valve covers so I suspect gasket. Went to Autoz Zone to get one and they have 2 different kinds---one "regular" and one "heavy duty high performance". They look different. Which one do I need? How can I tell without removing the valve cover? (I don't want to remove the cover until I have the time to put in the new gasket--my mechanic life tends to work like this--if the job takes the average guy 20 minutes, it takes me 4 hours!).

          I worked for a Mopar dealership back in the '70's, and Chrysler changed the 440 valve cover gaskets numerous times, by service bulletins. This was probably due to the advent of catalytic converters in 1975, and the extreme high temperatures of the exhaust manifolds....the gaskets literally cook!! But be sure to straighten and check the valve covers carefully, whatever gasket you use.....and DO NOT overtighten!

          We serviced all of the NYSP patrol cars from the local trooper barracks, and valve cover gaskets were a constant problem on these cars (and almost all 440's) due to the high heat and close proximity to the exhaust manifolds. I believe Mopar did not want to re-engineer exhaust manifolds and heads for an engine that they knew was going to be eliminated by 1979, for a number of reasons.


          And, as stated by hemibee68, the valve cover gasket leak is NOT the intake leak; it will result in oil leaking on the exhaust manifold, but should not affect the engine vacuum. You need to find the intake leak too! :yeah that:

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          • #6
            Thanks for the help. Looks like I have a winter project with the intake.
            "Semper ubi sub ubi"

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            • #7
              Replaced most of the vacumn hoses over the past few months and that didn't help the vacumn leak. So I thought it was at the intake manifold.

              But now the Problem is solved!

              Had a friend come over yesterday and he immediately saw what my son and I had missed--a little plug on the brake booster had fallen off and that is where the air was coming from! I don't know how we missed that before except that maybe we had seen the oil leak by the passenger side valve cover and were focusing our attention on that side of the motor. For $1.49 the Imperial is fixed.

              p.s. We changed the valce cover gasket too.
              "Semper ubi sub ubi"

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              • #8
                Originally posted by tdzik View Post
                Replaced most of the vacumn hoses over the past few months and that didn't help the vacumn leak. So I thought it was at the intake manifold.

                But now the Problem is solved!

                Had a friend come over yesterday and he immediately saw what my son and I had missed--a little plug on the brake booster had fallen off and that is where the air was coming from! I don't know how we missed that before except that maybe we had seen the oil leak by the passenger side valve cover and were focusing our attention on that side of the motor. For $1.49 the Imperial is fixed.

                p.s. We changed the valce cover gasket too.

                Glad you got it fixed!

                An intake gasket leak is rare on the 440 engines, mostly on the smallblocks. But the 440 valve covers almost always leak!

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                • #9
                  B/RB valve covers are great for fogging mosquitos. Glad you found the leak and got it fixed.
                  The nine most terrifying words in the English language are, 'I'm from the government and I'm here to help.'
                  Ronald Reagan

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                  • #10
                    lol Changed lots of those valve cover gaskets too. I used to pickup performance gaskets for the mechanic who serviced our cruisers. The 440's sure did cook the gaskets. Still a lot faster than the 454 Chevys and much nicer to drive.
                    The design of the exhaust manifold was so close to the valve cover and as mentioned with the extra heat they didn't last long. Exhaust manifolds were known to glow red at times. Not good if a clumsy cop spilled oil when adding a quart.

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