Newbie question

[HemiRam]

Hey All- I recently picked up a 70 Challenger, 440 with a 6 pack. I never had a muscle car in my younger days and plan on enjoying mine now. I took it out on the freeway and ran it up and down a few times which was friggen awesome. I got home, shut it off and the engine knocked pretty bad for a few seconds before shutting off. Is that just a type of gas I used issue? I used the mid unleaded, should I be using premium?
Thanks

 

[Katfish]

Yes on the premium, and probably need to adjust the timing.

 

[tonysrt]

Could also be too lean, caused maybe by a vacuum leak or carbs being lean. Check the plugs to see condition.

 

[Ricks72Chlgr440]

Hey All- I recently picked up a 70 Challenger, 440 with a 6 pack. I never had a muscle car in my younger days and plan on enjoying mine now. I took it out on the freeway and ran it up and down a few times which was friggen awesome. I got home, shut it off and the engine knocked pretty bad for a few seconds before shutting off. Is that just a type of gas I used issue? I used the mid unleaded, should I be using premium?
Thanks

Several things could cause that. Idle speed too high. Engine timing is off. Engine valves and pistons have deposits that cause a hot spot. Pull a couple of plugs and look at their condition. That will tell a lot. Definitely use higher octane fuel if you can get it in CA. Until you get this resolved you can help prevent this by turning the engine off while in gear, if automatic.