94 xlt with 302 with lots of miles 188k. Engine makes a rat tat tat tat sound when under acceleration. Idles fine but I think I can hear a tat or two here and there. Very pronounce when acceleration but gone when gas is let off and cruising. Just bought the vehicle and never owned one before so I don't know what "normal" 302's sounds like. Tune up has been done already with all parts replaced already (spark, rotor, cap etc...)
No engine check lights or anything that I can see or think of that is wrong. Is this normal for it to sound like this?

 

You have just discovered spark knock. Get the fuel injectors cleaned, or add some fuel injector cleaner to the tank on fill up and see if it helps. Also, check the base timing. Needs to be 10 degrees btdc. You also have to remove the spout connector located near the ignition module on the driver's side fender before you check the timing. The timing chain stretches over time and alters base timing. Good luck.

Robbie

 

Could also be a leaking/cracked exhaust manifold.

-Jon

 

Mine sounded like that when the tube rusted off where the air gets injected into the cat. I purchased a new tube from Ford for a reasonable cost and it was a relatively easy install.