97 Silverado knocking at start

[HawgHunter74]

I just finished rebuilding my 97 Silverado. It's running fine but when I first start it there's a knock like there's a bad lifter or something. It goes away within a minute or so. It only happens when the truck has sat long enough to completely cool off. Any idea's what this might be

[MT-2500]

Tell us more about the rebuilt?
What engine?
New pistons? Cylinder walls bored? Crank miked and bearings to fit it?
Is the knock in the lower end or piston or upper end?
Can you short out the knock to a certain cylinder?
AC Delco oil filter?

[barbs1515]

I had a similar problem with my 98 gmc 1500. I posted a question about it a while ago and someone replied saying that it was a crankshaft bearing. According to him the 5th crankshaft bearing has a slightly different clearance than the rest and it causes a knock until the engine warms up. Over the weekend I changed my oil and put a quart of lucas oil stabalizer in it and it seems to help. On cold mornings I still have the knock, but it doesn't last as long. Hope this helps.

[etuke]

I have a similar knock when first starting the engine in the mornings but I figgured it was just that the oil pressure just took time to pump through the bearings.Mine goes away after about 3 or 4 secs.I have a 93 with the 5.7L.