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R1 engine run-on, death rattle, won't shut down without dieseling...

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  • Engine: R1 engine run-on, death rattle, won't shut down without dieseling...

    On my '63 Avanti R1, I have a severe run-on issue when turning off the key. I don't remember it being so bad in the past, but it's always had this to some degree. I've gone so far as to install an electric idle stop, so when I turn off the key, the throttle blades close all together, but it still does it a bit. I resealed the engine a couple years back, but other than that it is totally stock, and never had a rebuild, overhaul, or anything. I'm going to try some Seafoam to see it it will help remove the carbon deposits, and yes, I do run premium gas in it (At least I pay a premium for it!). No pre ignition or detonation when driving, but it rattles like mad when shutting it off. Does anyone with an R1 have this problem, and what do you do about it. I've resorted to shutting it off in gear, but being an automatic, (th700R4), that doesn't help a great deal.

    This thing sits most of the time, but I've run it enough to be sure the gas (or what we laughingly call gas now days) is fresh, so I don't think that is the issue. I suspect carbon buildup, but why so severe? As soon as the engine is warmed up, shutting off the key results in the death rattle and shake. Any thoughts?
    Corley

  • #2
    You may be running your engine a little too lean, excessive lean will increase cylinder head temperatures. The correct fuel mixture will also maintain the correct temperature. In an aircraft there is a control for rich and lean, there is also a cylinder head temperature gage, excessive lean will increase the cylinder head temperature on the gage. With this lean condition the engine RPM will also increase. When a chain saw is running out of gas the pitch increases as does the speed, this is the result of a lean condition. The engine will run fine at speed however at shut down the cylinder head temperatures are so high that it will continue to ignite the fuel and run on. The lean condition can be caused by, low float, plugged main jet or a vacuum leak. With a trained ear you can hear a higher pitch at the exhaust.

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    • #3
      Check your timing. A stock R1 10.5 to1 needs to be de tuned a bit. It also may be that the 'fresh gas' is a bad blend. Try draining some out... It needs to be premium to even run at all. You might run through the valves to be sure they are set not to tight. Most people can't hear or feel pre detonation unless it gets really bad.. The fix is some thicker head gaskets/ mild porting and careful tuning.

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      • #4
        On R1s I always recommend blocking the exhaust crossovers in the intake manifold, removing the exhaust heat riser butterfly in the spacer below the exhaust manifold and slightly lowering the float level setting in the carburetor.

        What is the water temperature when shutting down the engine?

        jack vines
        PackardV8

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        • #5
          Run-on is common problem with our Studes in warm weather. If it's a stick, simply shut it off in gear then let the clutch out. If not a stick, adjust the idle screws to slow idle down as much as practical, and also shut it off in gear (idle is even slower in gear), but don't forget to put in in park afterward. My 56J runs-on if idling much above 750, as do most carbed Stude V8s. With the WCFB I recently installed, I set the idle to 650-700 and it has not ran-on yet. It it develops a problem later when weather gets hotter, I will drop it to 600-650, or even a little less. Of course it's no longer a problem with the two GTs, since I installed EFI on them. They both idle at 650-700, when warmed up.
          Last edited by JoeHall; 04-25-2020, 02:18 PM.

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          • #6
            Interesting. One person suggest too lean, another suggests I should lower the float level, which should make it run leaner. Another suggests timing is off, but when the key is turned off, ignition is out of the picture (except if very retarded so it is overheating, which it is not). Another talks about manual transmissions, when I clearly stated it is an automatic th700r4. Forgive me for being crabby but you gotta read the post!

            Jack Vines, I've removed the heat riser, but did not block off the intake preheat channel. It does not overheat, since the radiator recore, it always sits on the 160 thermostat. (By the way, there is a Ford core that fits perfectly.) But it's the worst at run-on of anything I've ever experienced. The valves are adjusted a bit loose, I don't remember what I set them at, but it was on the high side after replacing the umbrellas. I thought I could fix it with the electric throttle stop, so the butterfly's would completely seal off, but it only helped a little bit. I'll try the sea foam, as I've had good luck with it de-carbonizing a Suzuki Samarai, but I'm not too hopeful. If that fails, I guess I'll pull the intake and block the crossover passages. Any other thoughts?
            Corley

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            • #7
              Sorry I did not read down far enough. So it has a 700R and you've been shutting it off in gear. What do you mean by, "that doesn't help a great deal"? What are the RPMs when idling and shut down in gear?

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              • #8
                What spark plugs are in it? Electronic ignition?
                "Burning Bridges...Lost Forevermore"......

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                • #9
                  Here is a solution for you to think about.
                  Engine run on is a symptom of a partially open carb throttle blade.
                  It has to be open enough to idle, but that might be enough to cause 'run on'.
                  Installing an a/c kicker solenoid and adjusting it properly will allow your idle, but will let the carb butterflies close all the way when you power it off.


                  https://www.edelbrock.com/idle-compensator-kit-for-all-edelbrock-square-bore-carburetors-8059.html



                  HTIH (Hope The Info Helps)

                  Jeff


                  Get your facts first, and then you can distort them as much as you please. Mark Twain



                  Note: SDC# 070190 (and earlier...)

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                  • #10
                    Dwain, on the plugs, I'm not sure right now, but I'll take a look and post. Good thought, if they are too hot, they could be glowing, causing a hot spot.

                    Jeff, great idea! But, if you had read the whole post, you would know that I already did that.

                    I just had another thought on it, which I'll test out today. When I resealed the engine, in a burst of genius, I replaced the tiny little PVC valve Studebaker used with a typical modern PVC valve off of a SBC. Perhaps that PVC valve is too big, letting it run-on from crankcase fumes. Some of my bursts of genius are not as inspired as others. When I did that, I also eliminated the breather out the side of the pan, (which always leaked, making a big mess under the car), replacing it with a valve cover breather, ala most modern pre-EFI V8 engines. ( Incidentally, it has very little/no blow by, and is not a "stinker".)

                    Another thought that I had is that I should check the throttle shaft bushings, as they could be passing enough air for it to run-on if badly worn. Maybe. I'll check that today as well.

                    It's been a couple years since I messed with this car much, so I'm a bit fuzzy on some details on it. (Too many projects!) But I'd like to make it run better, and then I might get inspired to worry about the bubbles under the paint on the nose, and then respray it. Being older than dirt, I don't take painting cars lightly any longer. It's a ton of work, and I don't like the fumes and dust. Really, I should just sell it and let someone else have at it, but I always loved the lines/look of the round headlite 63s. Trouble is, I have too many projects that I'll never be able to complete. Right now I'm installing a turbo charger on a model A Ford, just for fun.
                    Corley

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                    • #11
                      I think you should sell it, unless you just want to have one to look every once and awhile. Studebaker cars need to be driven, as it is better for them and for you too. If you have too many projects, decide long and hard which ones to keep and sell the rest. As me how I know.

                      Bob Miles

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                      • #12
                        My Avanti had a problem with run on. The timing is set correctly, the fuel mixture is good and I run 91 octane gas which is suspect for an R engine. The engine would still diesel periodically on shut down so reduced the idle speed bit and the problem has gone away. A higher octane fuel would be a better solution but things like avgas and racing gas are expensive and hard to come by. Bud

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                        • #13
                          A very easy attempt to is buy octane booster. Lower octane actually ignites faster. Sitting is not good. I would spend 9 dollars on a can of the stuff and see. Easy at least.

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                          • #14
                            Originally posted by Corley View Post
                            I just had another thought on it, which I'll test out today. When I resealed the engine, in a burst of genius, I replaced the tiny little PVC valve Studebaker used with a typical modern PVC valve off of a SBC. Perhaps that PVC valve is too big, letting it run-on from crankcase fumes. Some of my bursts of genius are not as inspired as others..
                            This would be an easy thing to check. Just block off the PCV, note how much the idle had to be reset as an indication of how much air is being pulled in through the PCV, then see if this changes the run-on.

                            jack vines

                            PackardV8

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                            • #15
                              I once had a 70 TA Challenger with the same problem. I figured the primary carb throttle plate was not closing far enough. I removed the carb and discovered the throttle plate would not fully close even when the adjustment screw was fully backed off. I ended up loosening the screws in the throttle plates which allowed them to center themselves in the bore which they did. Finally the plates totally sealed the bore when the throttle was fully returned. This solved the problem. It may not on yours but might be worth a try.

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