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  1. #11
    Join Date
    Nov 2006
    Location
    Shropshire/Wales Border
    Age
    49
    Posts
    5,981
    Re running on, you may be able to solve that in 2 mins with a screwdriver. Check your idle speed. Even a couple of hundred RPM's up can cause it to run on. You need it around 700-750.
    Lloyd B
    Current: Crendon #54 in build - 427 Side Oiler/Cobrajet Heads/Dual 600cfm Holleys/4 speed toploader/Vintage cast knock on wheels
    Dedion Dax/Clarkson 383 Chevy with roller 4/7 swap cam, AFR195 heads - SOLD

  2. #12
    Join Date
    Sep 2010
    Location
    Nova Scotia
    Posts
    877
    Quote Originally Posted by Lloyd Barnes View Post
    Re running on, you may be able to solve that in 2 mins with a screwdriver. Check your idle speed. Even a couple of hundred RPM's up can cause it to run on. You need it around 700-750.
    Yes, however I have a theory on that. First, take a new or freshly rebuilt engine. and run it at 2000 rpm for 20 minutes to do the initial break-in. I normally adjust the idle screw for the 2000 rpm, so when I'm done and I shut it off, the carb is definitely too far open. Yet it doesn't run on.

    An older engine that has carbon build-up can having glowing red-hot carbon that ignites the fuel after the ignition is switched off. This is exacerbated by a carb that is too far open. Turning down the idle may stop the run-on, but your engine may still be carboned up.

    At one time (and maybe still) there were a lot of top-end cleaners out there that you trickled into the carb when the engine was idling. After a while of that, you took the car for a healthy run so the loosened up carbon would come off and go out the exhaust.

    Apparently these "cleaners" were 90-some-% kerosene, so dribbling a bit down the carb when the engine is at idle would probably do the same thing.

    My Cobra engine went for a while with a little run-on, but one day that suddenly stopped. I suspect it was after a particularly exuberant run, although I never did remember for sure.

    I'm not recommending the kerosene trick as it could cause a fire if something else is wrong with the engine, but I have used the store-bought additive on an old Lincoln with a 460 in it, and it did seem to work... mostly.

    Besides the "high-idle" causing run-on, I've also heard that "too far advanced ignition" could cause run-on, but that doesn't seem right as the ignition is turned off (unless it's wired to the alternator by mistake). But it could be the advanced ignition is causing a high idle.

    As the pinking could be your ignition timing being too advanced, it occurs to me that if your distributor hold-down bolt is not tight enough, the distributor may have slipped (although one would think it would slip in the direction of retarding the timing, but maybe not). If that caused the timing to advance, it would also increase your idle. You may have one issue causing two problems.

    I thought of replying to the original post when I first saw this, but lack of experience on my part, held me back. So I've presented it as a theory for now. You can at least check your timing easily enough and if it is a bit too far advanced, it may fix everything.
    John

    “A prudent person profits from personal experience, a wise one from the experience of others.”

  3. #13
    Join Date
    Feb 2007
    Location
    West Sussex
    Posts
    8,860
    Just remembered this place....
    http://www.thunderroadspeedshop.co.uk/
    Crendon Chassis No.49
    Huddart FE428 + toploader

    Not listed in the Shelby Register.

  4. #14
    Join Date
    Feb 2016
    Location
    Surrey
    Age
    54
    Posts
    109
    Thanks guys. I’ll work on this info and try on of the garages

  5. #15
    Join Date
    Jan 2006
    Location
    Chelmsford Essex
    Posts
    1,165
    Nice to attache a vacuum gauge and see what vacuum you have to check for any erratic vacuum readings. Also you can carry of your idle fuel adjustments . They are inexpensive tool to buy.

    Pinking and run on do have a common factor which is advanced engine timing. You can also use your vacuum gauge to set this but I would also use this with a timing light. A slow crank then fires also can be advance timing as the firing is happening at the incorrect stroke time.
    Dax 351 Cleveland T5 2.88 PL

  6. #16
    Join Date
    Jul 2013
    Location
    Hertfordshire
    Posts
    522
    Yes, Cheng is your man for this. 5 mint from the M25/A10 junction.

    When my engine was rebuilt by Mike Huddart he said a lot of people run the carbs far too rich to bump up performance which causes unburnt fuel to remain in the cylinders leading to engine failure.

  7. #17
    Join Date
    Sep 2009
    Location
    Leeds
    Posts
    2,934
    re running on - what fuel are you using, normal unleaded or super e.g. V-Power? mine would not run on when i used v-power, albeit i did end up having an full engine rebuild due to other issues with the engine - doh!

    Gary
    Conny - A Carnival Red Metallic (paint code Ref: Jag CGG/1811) Southern Roadcraft V8 ( SRV8 ) with 383ci stroker chevy.

  8. #18
    Join Date
    Feb 2016
    Location
    Surrey
    Age
    54
    Posts
    109
    I do always use V power

  9. #19
    Join Date
    Dec 2008
    Location
    West Sussex
    Age
    62
    Posts
    210
    One more for V Power. Tried the 97 octane BP, nope ran on sometimes. With V Power never runs on.
    Baz

  10. #20
    Join Date
    Feb 2007
    Location
    West Sussex
    Posts
    8,860
    Quote Originally Posted by jon1d View Post
    Nice to attache a vacuum gauge and see what vacuum you have to check for any erratic vacuum readings. Also you can carry of your idle fuel adjustments . They are inexpensive tool to buy.

    Pinking and run on do have a common factor which is advanced engine timing. You can also use your vacuum gauge to set this but I would also use this with a timing light. A slow crank then fires also can be advance timing as the firing is happening at the incorrect stroke time.
    another +1 here for the vac gauge.
    Crendon Chassis No.49
    Huddart FE428 + toploader

    Not listed in the Shelby Register.

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