today when i turned off my 68 after a while of cruisin to some antique car lots my engine gave a shake and a knock!!!but then every time after that it didnt do it whats the deal..?what if it starts this every time?carb?timing?thanks

No big deal here --just that it was idling to fast when you turned it off. This is called runon or dieseling caused by hot spots in combustion chamber. If it still does it, just slow down your idle speed.

Could also be bad gas. If it does this often, try switching to premuim.

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Bob Von Kaenel
70 SS 402ci TH400

Usually one of two things. Motor is running too hot or it is running too rich.

If I just get in the car cold and drive for 5 minutes and then shut it off it always runs on a bit because the choke is causing it to run rich.

Later
Steve