SBC Cam bearing Question

[Hot Rod To Hell]

Ok. I was cleanin my block and looked at the front cam bearing, which looked fine; COMPLETELY fine. All of the rod and main bearings looked great too, so I wasn't too surprised. But then I got this wierd feeling that I should check the other cam bearings. The rear bearing looked just as great as the front; BUT... The 3 middle bearings are FRIED!!! http://www.jalopyjournal.com/ubbthreads/images/graemlins/confused.gif The journals on the cam look perfect, but those 3 bearings are gouged, and flaking on the bottom of the ID. What in the heck would cause those 3 to take a crap, and all of the other bearings in the motor to look great??? My only hypothosis is that those bearings were installed incorrectly, or damaged during installation. Any ideas guys???

In case it matters, it's a solid roller, .632 lift, springs to .660 with a thrust washer and roller button.

[FWilliams]

somebody probably gouged them installing the cam.

[Hot Rod To Hell]

I put the cam in myself, and I am fairly confident in my abilities, So I don't think that was it... but I guess anything's possible. Any other ideas?

[Fat Hack]

I was thinking shakey installation of the cam myself, or maybe carelessness on the part of whoever installed the bearings. Believe it or not, I see alot of rebuilt engines with hastily installed cam bearings that are either nicked up or installed in the wrong position.

(Some engines required that the cam bearings be installed in a specific location to allow for proper oiling.)

If incorrect or careless bearing installation was the culprit, it's not a big surprise that the three cam bearings got wiped and the cam looks okay...the metal in the cam journals is much harder than the soft metal in the bearings.

If you're rebuilding this engine again, a fresh hot-tank will require new cam bearings anyway, so check 'em out good before cam installation this time around!

[draggin'GTO]

The high spring pressures required to run the roller likely thrashed them. The cam flexed downward enough to trash the three middle cam bearings.

A buddy of mine who runs a roller in his street Pontiac had the same problem until he spent the dough to install roller bearings in place of the old cam bearings.

Another real possibility is that the cam bearing bores are pulled out of line and are in need of align boring.

----- Bart -----

[Hot Rod To Hell]

Well to be honest with ya guys...I had this short block built for me by what a thought to be a reputable company (I don't wanna talk trash about anyone, so we'll just call this company Suck-E-Motors) And so far, it was suppsed to be done in 3-5 weeks, and took 9 months. When I finally got it they had put the wrong rear main seal in it (it was supposed to be align bored and wasn't, but they still put the align bored 400 rear seal in, and proceeded to crush it when tightening the rear cap) Which of course I was lucky enough to discover once the motor was in and test fired and spewing oil all over the place! http://www.jalopyjournal.com/ubbthreads/images/graemlins/mad.gif The Block was supposed to be zero decked, but all of the pistons measure .010-.013 in the hole. When I was tearing it down a few days ago, some of the rod bolts and some of the main bolts (splayed 4 bolts with studs) were noticibly looser than others (WAYYY undertorqued), and the two splayed bolts on the rearmost 4 bolt cap had galled threads, so I checked the block and they fucked up when drilling the holes, and tapped them crooked to match! I also have another post going about piston rings, cuz I'm pretty sure they screwed that up too. After all of this crap I DEFINITELY would not be surprised to find that the cam bearings were installed incorrectly. Just wanted to see what you guys thought...

[Fat Hack]

Damn, did they KISS ya first??? http://www.jalopyjournal.com/ubbthreads/images/graemlins/shocked.gif

Seriously, sounds like a bunch of Bozos screwed that motor together for ya. Consider yourself lucky that it lived this long without self-destructing!

I've bought a few lemon motors myself...live and learn, I suppose!

Just means ya gotta build one RIGHT this time around, eh??

(Meaning, ya gotta do it yourself!)

Sorry to hear about it! http://www.jalopyjournal.com/ubbthreads/images/graemlins/frown.gif

But, it's only a small block Chevy! http://www.jalopyjournal.com/ubbthreads/images/graemlins/tongue.gif http://www.jalopyjournal.com/ubbthreads/images/graemlins/wink.gif http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

[FWilliams]

[ QUOTE ]
Another real possibility is that the cam bearing bores are pulled out of line and are in need of align boring.



[/ QUOTE ]
hey, whats it cost to have that done?

[Weldemup]

From the quality of work the shop has done on your block so far I wonder if the sloppy installation of the splayed main caps has put a twist into your block?
If cam bores are out of line they need to be align bored/honed,but if the previous machine work on the block is sloppy and inaccurate you will be time and money ahead if you start with another block.

[porknbeaner]

HRtH,
There's a lot to be said for building your own. Granted there's a learning curve, but I'm going to guess that you're way into that curve at this point.
I'm helping a friend straighten out an Avanti right now that was supposedly "Pro Built". What a mess, he had always built his own and had a little cash so went the pro route with this one. No he doesn't have a little cash. Enough said.
If I recall the cam bearings have oiling holes, if they aren't lined up the only oil they are going to get is runnoff from the drain.
Also it is real common to nick one when installing it. Shouldn't happen but sometimes it does, lotsa of time if the mechanic/machinist is in a hurry or just prone to sloppy work. That seems to be the case here.
Anyway, the cam usually doesn't want to go in, but you can force it. The result is trashed, or misaligned bearings. At the very least low bearing life.
A nicked cam bearing can be saved with a ream. I'll post a tech on a low budget cam ream this week. Never force the cam, period.
Now this doesn't rule out the wrong bearing installed, to start with. Maybe you can rule this out when you pull the old bearings, and see if you can find the part number.
Which brings me back to alot can be said for building it yourself. http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif