kncoggins

I've been searching the internet for 2 weeks trying to find someone with the problems we are having. No luck so far, so I hope someone here can help. We bought a 2005 Silverado, 5.3 L33 in August. 155,000 miles, was told lots of work was done on engine, lots of things we could visually see had been changed, and sound wise you could tell it did not have the original cam. First Chevy we've ever had. Our hobby for 26 years is buying old Fords and rebuilding them. Can't tell you how many engines we have rebuilt thru all those years, so we are not ignorant when it comes to engines. Had some issues with the top end (tapping noise) of the Chevy after our 1st oil change with required weight synthetic oil, so not knowing what was really done before we got it and with that many miles on it, we decided to get some rebuilt heads, installed new lifters, rocker arms, new oil pump with red o-ring, new oil pick-up tube. Push rods had been changed sometime before we got the truck. Comp push rods, all still straight and true, no blockage in tube. Not sure if lifters we replaced were original or not, but all looked very good, rollers had no scarring or any damage at all. Started engine with value covers off. Everything great on drivers side, where the original noise was coming from. Passenger side, #4 cylinder exhaust and #8 exhaust, no oil being pumped up from lifters for 1st minute, then pumping less than half the oil volume as all the others where pumping on that side. Thought maybe something got in the valve and stopped it up, flushed with Berryman. Changed oil. Same thing. Replace those 2 lifters with new lifters again, and installed new pushrods on those 2. Started it up again, same thing. Engine runs great, very strong, no codes being thrown to set off CEL so that is not lite up. Feel like blockage may be in oil galleyway going to those 2 lifters.Really don't feel like a whole new motor is needed but not knowing Chevy engines, not sure where to go from here.

Byrdman11

iTrader: (2)

First off I would check rocker hole align and wear against one that flows good. Second if it get oil you are ok. No way oil passage is blocked in block. When the oil get hot it will flow like crazy.

kncoggins

Thank you Byrdman11 for your suggestions. We didn't have time to work on it much yesterday, but here is what we have so far. Before checking the bolt holes, we started it up again to view how the pushrods where riding. The 2 bad ones were moving with no differences to the good ones. No wobble and same distance around the opening as the good ones. Just pulled the head, holes look the same as other visually, threaded bolts into bad spot and good spot, angle looks the same. Looking at the lifters, all the good ones were free of oil on top, bad ones still had oil puddled on top. Did we get 2 bad lifters again? Lifter slot slightly wore, even tho they sit as snug as the others? Something up with cam? Really hate to have to buy a new engine with Christmas coming up. All thoughts and suggestion greatly appreciated.

30thanniv

iTrader: (2)

Did someone use too much cam lube?

kncoggins

We were told when we bought the truck the cam had been changed out. Does not sound like stock cam, aftermarket gaskets indicate top end was at least opened up, but we have no idea. We have not messed with the cam so far, just rebuilt heads, new lifters, rocker arms. Husband is out tearing it all apart now. Guess we are a getting new one and stop the guessing of what the previous owner really did. Thanks for all the help!

JoeNova

The lifters all share oil from the same galley. If one has oil, they all have oil.

RockinWs6

Check the oil for small air bubbles, you may have a damaged oring on the oil pickup tube. The air travels up into the lifter gallery and causes trouble like this.