1977 350 Stock with badger flat top pistons, elgin cam eqivalent to edelbrock 2102. No other internal mods. External mods are headers, edelbrock intake/carb. I have developed a knock/rattle that sound like a spray can when you shake it extremely fast. Only very audible when engine is cold in the morning. When I start the truck I get a quick rattle like a lifter is pumping up then it becomes quiet. You won't hear it again until you drive away and put a load on the motor, more gas = rattle, let of pedal and it disappears. When warm you can only hear it if you are me, it is so inaudible you have to know what you are listening for. It's coming from the passenger bank 2/4/6/8 Oil pressure has always been good, 55psi at cruising, 18psi at idle. No fluctuations in the gauge, no overheating, does not use oil, no oil out of exhaust. Oil is clean, no water, no gas, no metal. It is very slowly getting worse over the months. I've always though it was the piston pin. Anyone else have any other ideas, I'd appreciate hearing them. ADDY: MSD ignition, timing is not overly advanced ie. spark knock.