Engine knocks when turned off

[dan m]

My 1969 Charger 383 4 speed is starting to knock when I shut the car off. It was tuned last year. I use non ethanol 90 octane gas. Is this a timing issue usually? It runs cool per temp gauge so it's not over heating.

[b5blue]

Pull the plugs and see condition. You may have carbon buildup and that retains fuel.  Do you do any extended runs to clear/clean it up?

[dan m]

Plugs were replaced last year. I'll try running it on the express way. I only put on about a 100 miles a year. It has about 49000 original miles on it. I thought maybe the timing might have slipped.  I add lead additive to the fuel also.

[John_Kunkel]

What's the idle speed?

[dan m]

I can't say what it is as I have a regular mechanic that works on it when needed. It does idle ok per an old time vacuum gauge that i put on it in 1970 to indicate whether it's getting good or bad gas mileage. It l looks like bike speedometer. Lol.

[b5blue]

Okay so in a year the plugs/cylinders can get plenty soot loaded. For years I drove my 440 to work 2 miles away, 2 miles home. I had to put a manual choke on it to keep it from loading up. Pull any plug and I'll bet it's black.

[dan m]

There used to be a product that you would run through the carb to remove carbon buildup. Any thoughts on using something like that on a 53 year old engine? The only engine work that I had done was a new cam, lifters and timing chain maybe 20 years ago.

[b5blue]

Do the express run and see first. 

[Kern Dog]

Only 100 miles a year? 

[dan m]

It stopped being a daily driver many years and speeding tickets ago. Lol

[Kern Dog]

If you bought it before 1970, you are old enough to be retired and with all the free time you have, you could be driving the car more. Short trips are not good.

[dan m]

You're right but with antique car insurance, you have limitations. I've been cut off a few times so you have to watch where and when you take it out. The roads are now full of rude and inattentive drivers. Plus a bad knee doesn't help. Hopefully it will survive another 53 years and go to someone who loves it like I do. I actually bought it in Feb. 1970. It saw only one winter. My late wife was mad at me for getting a four speed. She could only drive automatic. Praise the Lord. Lol

[b5blue]

LOL 

[Kern Dog]

You're right but with antique car insurance, you have limitations. I've been cut off a few times so you have to watch where and when you take it out. The roads are now full of rude and inattentive drivers. Plus a bad knee doesn't help. Hopefully it will survive another 53 years and go to someone who loves it like I do. I actually bought it in Feb. 1970. It saw only one winter. My late wife was mad at me for getting a four speed. She could only drive automatic. Praise the Lord. Lol

I have limited use insurance too but I have driven mine a LOT more since I converted it to a 5 speed. I also added A/C which was unheard of 20 years ago!
Back to your original point....
I've dealt with "run-on", detonation and other troubles. The run-on was cured by lowering the idle speed and switching to colder spark plugs.
Good luck.

[dan m]

I'll try lowering the idle speed for starters. Thanks

[John_Kunkel]

Keep in mind that some factory-new cars of that era suffered from "run on" at shutdown, even with the correct idle speed and good gas....the cure for many was an idle solenoid that closed the carb butterflies at shutdown.

[dan m]

This is something that just started. Maybe some bad gas. Supposed to be 90 octane non ethanol. I'm going to try a different station next time. Thanks for all the helpful suggestions. Living in NYS I'll probably have to convert it to electric. Lol One of the goals of these AOC politicians is to ban the use of fossil fuels like natural gas stoves and furnaces. I read that they want to stop the sale of gas powered vehicles by 2030. 

[mopar346]

Ya'll need to switch to Hagerty, you tell them how many miles you want to drive a year. Very reasonably priced too in my view.