So, I'm doing a cam swap for a friend of mine in his 96 LT4 C4. Everything is trucking along pretty smoothly, and then...

As I tried to remove the cam, it didn't want to move forward or backward. It spun freely, but with my tugging on the dowel pin it didn't want to move. Eventually, through a combination of tugging and turning, the cam slid free of the bearing journals. I gently turned the cam and worked it forward out of the engine.

Once I got to the second set of journals, the cam just stopped. It would not move forward. I looked down the lifter holes with a pen light and didn't see anything out of the ordinary. Then I looked in the front cam journal hole and saw something really odd. The number 2 cam bearing was still on the cam and was hitting the number 1 bearing keeping the cam from coming out.

I ended up sliding the cam back into the motor about 1/2 an inch, and then gently yanking the cam forward. This caused the stuck on #2 bearing to smack into the backside of the number 1 bearing. Each time I did this the number 2 bearing would move about 1/8 of an inch. After 4 or 5 whacks, the bearing came off and I was able to remove the cam. Here's some pictures.


This one is the number 2 bearing, still in the block. It looks to me like it spun inside the block. You can see in the back ground that there is no bearing in the number 2 journal.

[URL=http://img186.imageshack.us/my.php?image=bearing1uo2.jpg][/URL]

This is the number 1 bearing surface on the cam:

[URL=http://img238.imageshack.us/my.php?image=journal1vq5.jpg][/URL]

This is the number 3 bearing surface of the cam:

[URL=http://img120.imageshack.us/my.php?image=journal3ld9.jpg][/URL]

Number 4 and 5 look just like number 3, so I won't post pics of those. This next pic is of the number 2 journal. Look at the difference in marring, and the difference in color. I don't know why, but it looks like something bad happened to this bearing and it stuck to the cam:

[URL=http://img247.imageshack.us/my.php?image=journal2vf7.jpg][/URL]

All in all, I'm not really sure what happened. Anyone have any ideas or guesses on what might have caused this? The engine is practically brand new, having less than 3000 miles on it.

Any thoughts?

poor oiling? incorrectly installed bearing? Cam bashed the bearing on the way in?

Those are my guesses. I would like to hear what Cuisinartvette and CFI have to say.

New engine or rebuilt? About the only thing I can think of that would cause that would be the obvious stuff:
1) the bearing was improperly set or improperly sized
2) oil starvation
3) lack ck of cam lube on start

Anyone else?

Seazed and was using block for bearing surface. Crud in the oil gallery?

The motor is rebuilt.

New crank, bearings, and rings. Stock pistons and rods. I do not know if the cam bearings were replaced during the rebuild.

Quote:

It certainly appears to be an oiling issue. From the looks of your photos the cam lobes also appear to be wearing excessively. Sorry to say that it seems your friend is looking at another rebuild. I think dropping the pan is in order to check the condition of the crank bearings.
Your also going to need to find out where the oil pressure loss is. Not real familiar with the LTx oiling system,possible oil gallery plug problem?
Cam bearing spun in the block isn't good.

the oiling is very much the same on the LT1 as it is on the L98.

To fix this right will more than likely require a line bore of the cam bearing journals and oversized bearings to fit right.

I wonder if the block was properly cleaned and some goo was left in the various passages.

You will need to pull the engine to address the cam bearing issue. A thorough cleaning and rodding of all oil passages is in order. What kind of oil was he using? I suspect you will find abnormal wear on the other bearings.

Why was it rebuilt? Why did it need a new crank? Who rebuilt it?

The motor in question is mine.the motor was rebuilt due to a worn out thrust bearing on the crank.It was walking so much the counterweights were hitting the block.It was line bored and another crank was installed with new rings,bearings,and oil pump.
It has less than a 1000 miles(more like 500).
It was rebuilt at a reputable machine shop in Durham NC.The tuner was the middleman and did the R&R and some of the assembly.I do not intend to name him until he has had a chance to see it and fix it.
Is this block still usable??

Depends on the result of the post mortem. If there is nothing more than a spun cam bearing, it should be. At any rate, it will require removal and a complete teardown and cleaning to remove all the bearing debris.

You have had two premature and unusual failures. I would be extremely suspect of the whole oiling system. Were the cam bearings changed when the crank was?

Either the cam bearing wasnt lined up with the oil hole properly, debris got in it or (my choice) a cam journal or bearing was sized incorrectly (too tight) to begin with.
more than likely I bet it was a sizing issue. Rare, but happens.

:withstupid]COULD[/i] have better lighting to bring out all the details, and they could be in better focus, for the same reason, especially fully expanded. BUT what is so great is the thumbnail feature. You have HUGE pictures, too huge, in my opinion for the focus, but with the thumbnail feature, they don't stretch and distort the format. Also, being that huge, they took too long to down load, but another great feature of THAT thumbnail, is the size was noted on the thumbnail, so a guy knew what he was in for before he clicked on it. I'm signing up with Image Shack immediately. Until the new programming arrives, something like that ought to be mandatory on this forum.

RACE ON!!!

Hey man, my camera is state of the art! At least it was in 1995 when I bought it, lol.

Quote:There is nothing wrong with a state of the art 1995 camera. All you need now is a 1995 photographger.

Kudos, again, for the thumbnail treatment.

RACE ON!!!

Thanks for the props. Photography, it appears, is not my strong point. I guess I'll stick with my strong suits; drinking and hiring hookers.

It appears that the engine builder is going to cover the cost of a rebuild. At this point, talk is cheap, but at least it looks like it's headed in the right direction. I'll update as I know more.

Wow a simple project gone awry....

Hope it turns out better than it started..