99 Monte Carlo 3100 V6 Cam BROKE

[Robenstein]

Had a good one come in to my fathers shop. 99 Monte Carlo with a 3100 V6 with the cam broke in two. In all my years of working on these engines(head and intake gaskets especially)I have never seen it happen. Engine was original and had 130k on the odometer.

How the heck do you think it happened? Im thinking the 16 YO with his new license thought he had a fast car and had a lead foot.

 

[-Clayton-]

My moms 97 Lumina with the 3100 Broke the camshaft into a couple years ago. Since the oil pump runs from the cam and the engine still managed to run for quite some time it ruined the engine, I bought a junkyard engine for $250 put it in and the car is still running great today. The camshafts on them and the 3400 are hollow and it happens every once in a while.

 

[Quest]

To be honest with you: it is not uncommon to see NA OE cam to go bad due to improper casting/hardening and/or break-in.

Q.

 

[Robenstein]

I know but wouldnt it happen a lot earlier than 11 years and 130k miles down the road?

 

[FL_Rob]

Where did it break ?right in the middle?

 

[SuperEd73]

I know one of my brother's friends had a Chevy Venture mini-van with the 3400 V-6 and the cam snapped as well. Perhaps the engineers went a bit too thin with the cam walls to try and save weight or rotational drag to improve fuel efficiency? When I first heard the story I was befuddled but that was before I learned the camshafts are actually hollow.

Ed B.

 

[Robenstein]

Originally Posted By: FL_Rob
Where did it break ?right in the middle?


It broke into pieces that are about 65 and 35%

 

[FL_Rob]

Holy c**&*%$

 

[mechanicx]

There was some kind of manufacturing problem with the cam durability and breaking around the '99 model year. It also doesn't help that the lower IMG tends to leak and coolant can run down on the cam.

 

[punisher]

One of the few internal faults I ever ran into on the FoMoCo 3.0 Vulcan was a broken cam. I stuck my MIG in and tacked it back together, and pulled it out. Big occlusion in the casting. Replaced the cam, and it ran great.

 

[Robenstein]

Originally Posted By: mechanicx
There was some kind of manufacturing problem with the cam durability and breaking around the '99 model year. It also doesn't help that the lower IMG tends to leak and coolant can run down on the cam.


I replaced the intake and head gaskets in that car the summer before when I was turning wrenches while college was out. No coolant was leaking in the oil unless Fel Pro made a bad set.

 

[onion]

This is a fairly common failure on the 60-degree GM V6 engines. Google it.

 

[mechanicx]

Originally Posted By: Robenstein
Originally Posted By: mechanicx
There was some kind of manufacturing problem with the cam durability and breaking around the '99 model year. It also doesn't help that the lower IMG tends to leak and coolant can run down on the cam.


I replaced the intake and head gaskets in that car the summer before when I was turning wrenches while college was out. No coolant was leaking in the oil unless Fel Pro made a bad set.


Well it sucks that you replaced all those gaskets and had one of the defective cam model years. It is really a decent engine if it weren't for those issues.

 

[Robenstein]

Originally Posted By: onion
This is a fairly common failure on the 60-degree GM V6 engines. Google it.


Funny that this is the first I have seen or my father has seen. He has been working on them since they came out. Saw lots of blown engines from coolant leaks, but this is the first busted cam.

 

[onion]

Don't know what to tell you. I've seen two. And Google will show you plenty more. Seems that the standard failure mode is for the intake gaskets to fail, subsequently a cam bearing locks up... and the cam breaks.

That isn't to say that it couldn't happen some other way too.

 

[Robenstein]

Yeah the bearings looked good and there was no sign of coolant leaking. Sometimes odd things just happen. The kid thinks the car is "fast" so I am betting he was beating on it and that may have helped a bit on busting the engine.

 

[Quest]

regularly pushing it to the limits has nothing to do with cam snapping; a poorly casted/hardened cam does.


Q.