When I cold start I get a rod knock for a few seconds. It completely goes away after oil pressure comes up. When I warm start it does not knock. My oil pressure runs above 20 psi at idle. I am running synthetic castrol 5-50w oil. Is this something to be concerned about?

Is it a knock or is it a tap ? if it is a knock than there is something definetly wrong inside your motor! I had a 350 in a suburban and did the same thing, it would go away after oil pressure stablized and i drove the truck for awhile before i pulled the motor to have look and sure enough one of the rear rod bearings was toast, another time on one of my big blocks had a similar noise and it turned out to be the rear cam plug. but anyway my point is this your motor is telling you something is wrong and right now it may not be that bad but it WILL get worse

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R.Chambers
69 rs327 a/t & SS396 m/t

Does the ZZ3 have forged pistons? Sometimes when cold you will hear a slight knocking, bumping noise for a second or two when the engine is cold, My 74 Z-28, L82 did it for the 5 years I owned it.

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69 rallye green X77 Z/28,1967 SS 396 Conv. 1974 c-10 454 swb

Rod knocks don't go away when the engine gets warm they get worse. It sort of sounds like a lifter is bleeding down over nite.

The pistons are cast hypereutectic aluminum. The lifters were tapping a bit but I adjusted them and I now hear a faint tap once in a while. Doesn't happen all the time. This sounds metalic rather then a tap. When I cold started this morning there wasn't any noise but most the time there is for a few seconds. Engine has about 8000 miles on it.

it sounds like lifter bleeding down to me as well,but ive heard of what sounds like rod knock at startup being caused by the crank actully "walking" once running it settles down i beleive this related mopar but maybe it will help.