I have a 77 f250 with a 400, and it makes a sound that sounds like a rattling shield or a ticking above 3 grand. It won't make it if I accelerate hard or anything except when the rpms get high enough. It also seems to make the noise at lower and lower rpms as the engine runs longer. Could this be pinging/detonation? I haven't changed anything, and it runs great otherwise. I'm going to check my timing tomorrow just to double check, but like I said, it runs great, and with 8:1 compression it would have to be pretty far advanced to cause detonation correct? Should I try octane booster? I tried 89 octane instead of 87, and it made no difference. I'm stumped. Any help is greatly appreciated.

 

if it is pinging , don't let it do very long!, 400"s were very prone to pinging due to the combustion chamber shape, back your timing off a bit, more octane won't really help, especially if you're using even a bit of oil

 

Hi-miler engine ?

Near the end ...My 400 pinged right up to its death at 325,000 km

If the timing gears and chain are so stretched and worn out no amount of adjusting the dizzy or higher octane will make a difference.

Do a timing chain slop test.