3100 SFI...in a GOOD friend's '95 GP SE...BROKEN CAM SHAFT!! ??? help!

[ChurBoywithALLthemGRANDS]

GUys, FIRST off I REALLy appreciate you OPENING this.

 

Has anybody EVER heard of the 3100 BREAKING one of the Cams? (the mechanic said the cam that opens/closes 2 cylinders?) Not really sure what he means...

 

Mechanic said there are only 2 WAYS this could've happened.....

Running the engine with VERY VERY low oil and, having no friction caused it to 'snap'.

or

My buddy's wife just plain BEAT on her Grand Prix!

 

 

From what I said above, does this sound WORTH fixing and IF SO, where could we get the part?

ANYBODY know of any NEW or low-miles 3100 engines for sale? Just replace the whole thing MAYBE...as it has almost 100k on it now. (Not 'bad' for a 3100, but you know....still better to have a NICE new "perfect" engine)

 

GEARheads....could chu please holla at 'Chur Boy?' haha THANKS A MILLION GUYS! Best site ever!

[DaveFromColorado]

sure it's the cam, and not the rockers ... those rocker studs have been known to pull out of the heads - not often, but it does happen. It'd give the same signs of a bad cam.

 

--Dave.

[ChurBoywithALLthemGRANDS]

REALLY.....Hmmm. So, that'll be something I'm def gonna consider. Dave, is this problem FIX-ABLE? or does this '95 GP need a WHOLE new engine bro?

 

Thanks for the input...

[Robby1870]

If the rocker stud is in fact broken, all it would need is a new rocker stud, a very easy fix. A rocker arm or other valvetrain component might be damaged too, but those are also easy to fix

[Calvin]

Come on guys, its not a rocker stud thing.

 

We all know that the 95 3100 is one of the worst years for the intake manifold gasket leak, that drops coolant into the cam bearings and seizes them up. Then the cam, (which in these cars is a hollow steel tube made by pressing the lobes on by putting them in postion and then forcing a titanium steel ball through the inside of the tube, swaging the cam) twists off and breaks toward the back of the block where the leak drops coolant in. Thus, broken cam, which happens in these all the time. You have two options: COMPLETE rebuild, or finding a JY motor in good shape to throw in.

 

Kurt

[Robby1870]

Come on guys, its not a rocker stud thing.

 

We all know that the 95 3100 is one of the worst years for the intake manifold gasket leak, that drops coolant into the cam bearings and seizes them up. Then the cam, (which in these cars is a hollow steel tube made by pressing the lobes on by putting them in postion and then forcing a titanium steel ball through the inside of the tube, swaging the cam) twists off and breaks toward the back of the block where the leak drops coolant in. Thus, broken cam, which happens in these all the time. You have two options: COMPLETE rebuild, or finding a JY motor in good shape to throw in.

 

Kurt

 

Our whole point is that yes, it could be a broken cam, but it would be very easy to verify that it's not a valvetrain thing. No since in replacing a motor for a broken rocker stud. It's something easy that can be verified.

[94CutlassXtreme]

I doubt the motor will be at all salvagable. A 98 N-Body Cutlass with a 3100 came in to my school's shop with a seized engine and I guessed broken cam, and I was right. The cam had broken right in the center, and seeing as the cam drives the oil pump, the engine lost oil pressure and the center cam bearing spun the bearing and in turn "bored" the bearing loacation out. This engine also had a noticably bad intake gasket and a bent pushrod, most likely due to the cam. Poor, poor, 3100

[ChurBoywithALLthemGRANDS]

Robby...thanks for letting me know that man. DEF something I'm going to tell them to look for.

 

And KURT....I awesome info, you really know your stuff. Sadly I think YOU are probably correct ...going by what I've HEARD about the 3100 engine. My good friend's 95 GP had to have a whole engine replacement b/c the coolant got into the oil and seized the shit out of it.

Sorta scares me as far as my '96 Grand Am goes....111k miles! Getting uP tHeRE! ahhh!

[bigdman]

i have a 3100 in my garage that was given to me because the cam snapped. the previous owner said that every once in a while it would start, but then run rough. well i got the top end off and sure enough the cam came out in two peices. hopefully this is not your case, but if so good luck

[IRONDOG442]

As I remember it, the machinig company that GM outsourced to cast and machine their cams used an "experimental" forging technology very similar to the way titanium is pressed into shape... using insane amounts of pressure and heat. The thin areas of the cam were subject to snapping and breaking in two. The problem is half of the engine keeps running and the other shuts down because the half of the cam that is still chained to the crankshaft and the other is basically stationary this usually sends the broken pieces of the cam through the oil passages and destorys the lower end of the engine. THis could lead to valve damage and or piston damage as well....GM denies this is a problem to this day and there is a forum dedicated to 60 degree v-6 owners complaining of this problem SOLELY. This was a very common problem in the early 3400 SFI engines in Pontiac Montanas and Chevy Ventures but have not heard about it in W bodies, anybody else know what I am talking about??

 

 

[DaveFromColorado]

this is the first time I've personally heard of this happening - however, I've repaired 3 rocker studs which have pulled out, and replaced one camshaft on a 3.1 (pre 3100) which actually wore the cam lobe down to nothing.

 

I say pull the intake manifold, and valve covers, and turn the motor by hand and watch all the parts to verify they are moving in the proper fassion. no better way to find out other then looking directly at the parts themselves.

 

--Dave.

[cryptnix]

i got a 3100 i can sell to ya ... has a 160k on it but ...

[ChurBoywithALLthemGRANDS]

160K! haha....does it run good? Any leaks?

How do you have a 3100 available to sell? it IS currently in your car right?

[Rocketman]

people sometimes have spare engines...

[Calvin]

As I remember it, the machinig company that GM outsourced to cast and machine their cams used an "experimental" forging technology very similar to the way titanium is pressed into shape... using insane amounts of pressure and heat. The thin areas of the cam were subject to snapping and breaking in two. The problem is half of the engine keeps running and the other shuts down because the half of the cam that is still chained to the crankshaft and the other is basically stationary this usually sends the broken pieces of the cam through the oil passages and destorys the lower end of the engine. THis could lead to valve damage and or piston damage as well....GM denies this is a problem to this day and there is a forum dedicated to 60 degree v-6 owners complaining of this problem SOLELY. This was a very common problem in the early 3400 SFI engines in Pontiac Montanas and Chevy Ventures but have not heard about it in W bodies, anybody else know what I am talking about??

 

 

 

I suppose you could call it forging, but I think it would be more correct to call it tube swaging (swaging is a diametrical upset). You're right about it being relatively experimental, as far as I know no other company besides GM does it this way, but they do it in house here in Bay City at GM Powertrain, where cams are made for almost every GM product out there (L6/5/4, High Value/Feature/ LS blocks, etc.)

 

I have a buddy who works in the plant and he showed me one of the titanium balls they press down the cam tube and its like a big, expensive marble.

[dbtk2]

The broken cam is definately a big issue. I've seen a few myself.

 

The engine I got for my topend swap came out of a '97 cutlass supreme (i used everything but the heads off of it) had a broken cam. Only the first 4 cylinders had the valves opening. The engine had no oil pressure obviously because the oil pump wasn't being driven. Yet the person drove the car to the shop to get the engine replaced. Both head gaskets were blown as well due to the overheating (no oil) and warping the heads. That engine looked pretty damn bad inside. Nothing wrong with the intakes or TB though.

 

The thing ran and drove though...it actually didn't even sound like it was running that bad either.

[IRONDOG442]

Calvin, I would like to see a pic of this marble you speak of... sounds like a very interesting process to make cams, do you think it's a good idea???

[Calvin]

LOL, it looks like a big steel ball, but tinted differently. If you saw it in person you would be like "this isn't even worth taking a picture of"

 

Is it a good idea? Well, if by good idea you mean cheap, then yes. For mass production you end up shipping out less lbs of metal per unit, and you don't have to heat treat as much, or grind as much, and precision grinding is a relatively expensive procedure in mass production, believe it or not.

 

For regular people tooling around they work fine. I don't know what their limits are in performance applications, but I do know that the only time they really fail for most of us messing around on the street is when their bearings are seized, and you can't blame them for that.

 

 

[Brian P]

the majority of broken cams I've seen in 3x00's were from engines that ingested a LOT of coolant into the crankcase (LIM gasket failure) or had happened to it in the past.

[Calvin]

the majority of broken cams I've seen in 3x00's were from engines that ingested a LOT of coolant into the crankcase (LIM gasket failure) or had happened to it in the past.

 

Yeah that's what I am talking about, the coolant displaces the oil from the bearings, and they get hot and seize.

[Brian P]

agreed