LOUIS

My 90 pickup truck had 245k miles, manual transmission,developed noise when I rev the engine, go up hill, tried 93 octane gas the noise is less, but it is still there.the noise like the sound of Tamborine( music instrument). My timing is at 10 BTDC. Where is the noise come from ? How do I fix it? Can it damage the engine ?

Churnd

from what i've heard in the past, that noise is normal. it's just the fuel injectors opening and closing.

Skydigger

...but since the noise has "developed" you might want to check your valves.

Warren