CodyBoy

Doing a stock rebuild on my 00 5.3.

The front cam bearing was worn severely on the bottom and looked like a slight copper color. The top of the bearing had no wear at all and appeared the cam journal never touched at the top.

The rear most bearing was the exact opposite and the top of it was worn.

The journals look fine with no wear or scratches , the lobes look fine. How can I tell if the cam is worn enough to replace it? I don't have mic's and what not to measure this stuff.

Trying to get buy with less than a grand for this and so far so good. No new pistons and no new cam. Everything else will be new.

budhayes3

iTrader: (19)

Welcome to the site, a lot of good folks and good info here for ya

I wouldn't be too worried about the cam bearings looking the way they do as this is pretty much characteristic of GENIII engines. Every one that I've seen pulled apart has had the wear that you described, and I've seen dozens of pics of this through the years as everybody that sees one for the first time has the same reaction. As for the cam, using a mic is the way to go, but since you're winging it, I'd just check for signs of scoring and any nicks. Post up some pics of the cam and bearings and I'm sure that you'll get enough responses to help you out

TXSZ66AVLANCHE

iTrader: (7)

If there is ANY marks on the cam or lobes replace it. The cam bearings will need to be replaced as well. For $1000 you going to better off buying a used engine, even a partial rebuild can exceed 1k very easily.

CodyBoy

Used engine = used parts.

Machining is right at $400 for boil the block, new cam bearings, honed, grind the crank, disassemble the heads, check for cracks, pressure test, grind valve seats,reassemble.

All new bearings, rings, timing set, oil pump, gaskets and head bolts. A little over $600.

Coban

iTrader: (14)

Copper showing on cam bearings can be attributed to one of two things:

1) GM supposedly does a line hone after cam bearing installation

2) Tension from the timing chain applies a downward force on the bottom of the front cam bearing, the reaction force at the back of the block will apply an upward force on the rear cam bearing. This also correlates to the wear spots you are seeing.... In other words, I wouldn't bother replacing it.


The thing you learn from this site is the more complicated the home rebuilds get, the more likely they are to fail from messing something up.

TXSZ66AVLANCHE

iTrader: (7)

Sounds like you got it all planned out and don't need any advise ;-)

Obviously a used engine will have used parts...but so will a partially rebuilt engine. Do you plan on replaing your lifters? You can get a set of stock type lifters from GMPP for about $120

CodyBoy

No new pistons, cam, or lifters..

Lost oil pressure due to clearance in the cam bearings or bad oil pump and clogged up screen in the pick up tube. It was almost completely blocked with sludge.

The thing about a used engine is it would be used and need of rebuilding and I already have used. Seems like I would be in the same boat but to have to purchase something I already have. A used engine.

Worn cam bearings isn't a need for a new or used engine.

I cleaned up the camshaft and the lobes are perfect as well as the journals.
Just like a mirror. No pits, scratches, nothing.

budhayes3

iTrader: (19)

+1 on all accounts, and Coban is correct, seems like the GENIII engines very rarely fail unless they were not maintained, or if they were cracked open and rebuilt. Even engines that were done top to bottom at a machine shop seem to have issues. There have been more than one member here who has bolted in their freshly built engine just to have it fail shortly after...Atomic and TXsilverado are two recent members that come to mind. Makes me nervous about tearing down my LQ9 to hone and freshen up, but I trust my pop and his 40+ years of engine building mastery, and we'll be doing the work at his shop when the time comes

CodyBoy

Yea my first impression from the cam bearing wear was tension from the timing chain.
Pull the cam down into the bearing in the front and raise it up into the bearing in the rear.

I don't think its a big deal.