Detonation!
 

I have been having a detonation issue with my 69 plymouth stock 318. It pings steady until I get past 35mph. I have tried better gas, cooler plugs, and had the timing adjusted. Not sure how far the timing was set or which direction. I am going to get my own timing light and see what I can do. Would slack in the timing chain cause this? I havent check it yet but I assume its stretched a little. I dont want to change it but I will if it my solve this.

Thanks

button -

Are you sure it detonation??? An exhaust leak can sound very similar.

Definitely check the timing, you should be able to retard it enough to stop the detonation. If you have to retard it so much that the engine's performance suffers, then there might be something else going on.

Archer

make sure the timing is set correct 8-10 deg before TDC, check the vacuum advance and the mechanical advance in the distributor. Also check for any vacuum leaks that could cause it to run lean.
To check the timing chain Take the dist cap off, turn the motor CC maybe 1/4 turn. the Turn it clockwise and watch how soon the rotor turns. If the motor has a lot of millage It may be beneficial to change it now anyway as it probably has the plastic can gear. Get a 340 roller chain for it...