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  • Proper spark plug gap

    I was having some issues while driving my 29 Leatherback a couple of days ago.I hadn't run it for about a month. It was running a little rough at first, but after it warmed up-it started acting like it was starving for fuel. I barely limped home with the choke pulled all the way out. If I put the choke in, it would die. I fiddled with the spark advance and the GAV, but that didn't help. So far what I have done is pull and check the plugs(Champion W16Y's). They did not appear to be overly carboned up. Then I pullled the fuel line at the carb to check fuel flow. No problems there-lots of gas. The instruction manual says the spark plug gap should be .027. Everything is stock with a rebuilt Zenith. Is .027 the correct gap for a stock motor with W16Y's? Before I test drive it after cleaning the plugs I want to make sure the gap is correct. Someone had suggested to get it started and run it for awhile with the gas cap off and see if that helps. I can't imagine that's the problem as I have had the same gas cap since I bought the car 2 years ago and I have never had this problem before. Thanks as always, Smitty

  • #2
    Smitty, if you are not going for fine points, remove the gas cap and drill a 1/16 or even a 1/8 hole through the center. It won't hurt a thing but it will insure that there is vent to the tank. 1/16 is way large enough.

    It sure sounds to me like the cap venting was clogged.

    To answer your plug gap question, .027 will allow for a spark, and I will be the first to add, I run mine at .035 without problems, but then, I run the cheapo autolite plugs.
    You wana look waaay far up da road and plan yer route because the brakes are far more of a suggestion than a command!

    Comment


    • #3
      What manual suggests .027? Try .035 before you drill a hole. Also, if you use ethanol gas, it may have gone bad over 30 days.

      Comment


      • #4
        Actually Ray, the owners manual says .027 was the gap until it was updated in the Service Bulletins to .032 to .035 April '30.

        Ref p454 Service Bulletins
        Last edited by DaWizard; 10-30-2017, 09:45 PM. Reason: added reference page
        You wana look waaay far up da road and plan yer route because the brakes are far more of a suggestion than a command!

        Comment


        • #5
          Smit
          Your plug gap should be .035 but this is prob not your issue. When your pulling the choke out this richens the mixture by not letting as much air in. It sounds to me that your running lean so you may either have a fuel delivery issue or a vacuum leak.
          Make sure your points are set to specs
          3 ~ Tudor's
          Henry Ford said
          "It's all nuts and bolts"


          Mitch's Auto Service ctr

          Comment


          • #6
            Do the easy checks first. Hold the coil wire 1/4" from a head nut and see if you get a hot blue spark while cranking with the key on.
            If not, then make sure the points are clean and properly gapped, and if that checks out, then try a new condenser.

            Comment


            • Mike V. Florida
              Mike V. Florida commented
              Editing a comment
              "...make sure the points are clean and properly gapped..." that is where my money is.

          • #7
            Thanks for all your help guys! Here's what I've done so far. Removed & cleaned the plugs & set gap at .035. Cleaned and set points at .20. Removed gas cap and started him up. Ran rough. I let him warm up and put the gas cap back on. No change with gas cap back on. Let him idle for a while and backed out of the garage & took a short 1/2 mile drive. Ran really bad. This time pulling the choke out didn't help. It seemed to run better at 1/2 spark advance, but still crappy. Limped back to the garage & ran the gas out of the carb. Unfortunately I'm running out of time to head South for the Winter. So "Clarence" is going to get his final winterization and be covered up for the Winter. I'll have to get back to him next May. Thanks again, Smitty

            Comment


            • #8
              It won't take long too snug up the manifold retainer nuts. If they were loose, run it to see what happens. If they are tight and the gasket is not sucking anything past it then it won't take much longer to pull the carburetor apart and give it a look.

              Comment


              • #9
                Originally posted by Ray Horton View Post
                . Also, if you use ethanol gas, it may have gone bad over 30 days.
                I doubt the gas went bad in 30 days. Granted, my 95 Miata isn't a Model A, but I just filled up the gas (85 octane regular), the first time since early March, without a problem. I put less than 1000 miles on it a year so essentially the gas is always old. It sits for months. I hop in it, put down the top and hit 6500 rpm without a whimper. I don't use any stabilizer.

                Comment


                • #10
                  Originally posted by slammin View Post
                  I doubt the gas went bad in 30 days. Granted, my 95 Miata isn't a Model A, but I just filled up the gas (85 octane regular), the first time since early March, without a problem. I put less than 1000 miles on it a year so essentially the gas is always old. It sits for months. I hop in it, put down the top and hit 6500 rpm without a whimper. I don't use any stabilizer.
                  I always run ethanol free gas.

                  Comment


                  • #11
                    If you have 1 plug that tends to OIL foul, open the gap WIDER!
                    Dad Wider

                    Comment


                    • #12
                      How about plug gap for 5.5 and up heads?

                      Comment


                      • #13
                        Originally posted by plyfor View Post
                        How about plug gap for 5.5 and up heads?
                        Ok, here is something to think about for plug gapping, no matter the head configuration.

                        You have a coil that puts out pixies each time the points open and close, now this should be a constant. Now, you have a distributor that cause the coil to make those pixies jump. Now, let us say you have a gap of oh, .025 between the rotor and the cap, we know that the pixies can jump that far because at that point they are fully charged up and hungry to find a source for ground.

                        Now, let's say you gap the plugs at oh, .030, since the pixies are looking for the shortest route to ground, because the rotor to cap distance is less than the plug distance, they will be able to jump the distance at the plug.

                        Now, let's say you gap the plug at .035, this is getting into the area where the pixies are still able to jump the distance, but because they are kinda running out of breath at all the jumping and the distance they are having to travel, it takes a lot of effort for them to make the jump, but because there is no where within the circuit from the coil to the plug that is shorter than the .035 besides the controlled jump of the rotor and cap, they are kinda forced to use the gap at the plug.

                        Here is where we run into problems, if you were to start making the jump distance at the plug more than the .035, the pixies are going to start looking for another place to jump within the circuit from the coil to the plug. This could be inside the distributor, from rotor to cap, rotor to edge of distributor, between cap terminals, from leaky wires to the head, between the cap terminals, etc.

                        So, IF you have the perfect circuit from the coil to the plugs, you may be able to open that gap up to about .045, but in doing so I think you run the risk of loosing the pixies between the coil and the plug.

                        What I would do is if you want to run a wider gap than .035, do research and change the heat range of the plug rather than take the chance of loosing the pixies to somewhere they don't belong.
                        You wana look waaay far up da road and plan yer route because the brakes are far more of a suggestion than a command!

                        Comment


                        • Mitch
                          Mitch commented
                          Editing a comment
                          Those pixies are pretty damn smart huh

                        • DaWizard
                          DaWizard commented
                          Editing a comment
                          Yes they are, very smart!

                        • Big hammer
                          Big hammer commented
                          Editing a comment
                          And those pixes hurt when they jump to your arm!

                      • #14
                        I had a set of those plugs and they made the Roadster run horrible. I changed to a set of the Motorcraft TT10's, and car ran fine.

                        Champions are somewhere in the bottom of the local landfill now. I never had any luck with Champion spark plugs.

                        Comment


                        • #15
                          NOW, we're OVERTHINKING spark plug gaps I had an Old Datsun 510, with point ignition, cleaned the old plugs, snipped off the ground electrodes & drove it a week, that way. I did it to prove that Wide Plug Gaps DON'T cause hard starting.
                          Dad Showme

                          Comment


                          • Big hammer
                            Big hammer commented
                            Editing a comment
                            I knew someone who removed the spark plug shipping protectors, he didn't last at the job very long, it was a 240 ford inline 6 and it would not run after he was done

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