start up truck and let truck warm up before driving, there is no 6.2 rattle.
Start up truck and take off with no warm up period, 6.2 rattle is there.
What causes this?
is there a timing advance on these db2 pumps?

 

I think someone else will chime in on this , but I have owned a few 6.2/6.5 and I know what you are talking about. I believe the reason for this is low combustion chamber temps.

 

Everything is fine. It's your cold advance working which should also raise the rpm slightly.

 

I have an 84 6.2, and i have noticed that after starting up, there is a sort of high idle that last for approximately 5-10 min. after this period, you can hear the RPMs lower, and the engine purr more smoothly. I'm sorry for not knowing the correct name for this process, but that is probably what you're experiencing.

 

thats what i thought. that there was a cold advance, so thank you all for your help and input!!!!!