ive got a 97 bravada 4.3l vortec with a loud tic. when i start it up cold you cant really hear it but as it warms up for couple minutes your can hear it. gets faster and louder when you rev it. but when i put it in drive and step on the gas and brake it wont make the noise at all or very faintly, barley noticable. the sound comes from the passenger side mostly. so far ive replaced the push rods, rockers, washer and nuts, on the passenger side. also i replaced all the lifters when i did headgaskets 2 years ago. i will upload a video on youtube in a few hours.

 

Manifold cracked? or bolt rusted off?

 

Sounds like it could be a sticking EGR valve. Try cleaning it. Or get a mechanics stethoscope and try to find the noise. I would clean the EGR first and replace the gasket with one that has a screen in it.

 

Heres the youtube video i uploaded so you can hear the sound.

 

anybody know what this sound could be. in a couple weeks im gonna tear into this motor but want to know first some ideas of what it could be. thanks

 

bump