knocking sound

My Express 1500 van w/ 305 Vortec seems to have developed a knocking sound when first started when its cold out. It does last for awhile (until really warmed up) and goes away slowly. Was thinking a lifter but not sure. Oil press is good (according to gage). 5w-20 used Castrol.

Anyone know of any issues with these engines or of this situation in particular?

thanks

Sounds like a lifter. Try flushing the engine (you can find it in most parts store - it's expensive kerosine). Run it through the engine for a few minutes then drain and change the oil & filter. This can be repeated if the engine is really dirty, but be careful. The kerosine acts as a solvent and will pull a lot of dirt out as well as thinning out the engine oil. Only run the engine a few minutes and then change the oil and filter again. If this doesn't fix the lifter noise then you'll either have to live with it or else pay the expense of changing it.

Good Luck.

I bought a 2001 Express van with the 350 motor. Had the same problem when I started it up. Changed oil and added a quart of Marvel Mystery oil. Knock Went away never to be heard from again. Only run the Marvel for a thousand miles or so. Hope this helps ,write me if it does.

If you get some dirt in a lifter you will always have this problem until the lifter is replaced. My old motor had a bad lifter and it would be fine until the motor got hot then it would clatter away. Hated that thing.