Thread: Broken studs/Push Rod--> From bad Gas?

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Well, I went to the Good Guys run in Colorado Springs, and my trip back resulted in problems. This may be too long of a story for some to read. Sorry.

I got some bad gas on the way out. At about a half tank, my engine died. Acted like vapor lock. But checking under the hood, I found I still had fuel pressure at the pressure guage, and fuel in the fuel bowl.

After a couple engine stalling incidents at side of road, we got it started, and it seemed to run fine. I pulled into the next gas station, sensing possible gas problems, and filled up. Car ran fine.

Hind site tells me I should have not run the tank too low, but we did run the tank down to about 1/8 tank, and 5 miles before the exit we gassed up at, we noticed white smoke coming out the exhaust. By the time we reached the exit, the engine was pinging and knocking pretty bad.

We gassed up, and drove around the town for a bit. The knocking quit, but I had a miss. After some thought, I decided (maybe a bad decision) to head on toward home (no place in the small town open to get plugs). It was a good solid miss. I presumed the detonation blew a plug. Seemed like one cylindar was not hitting. I figured that we would gas up often, at about a half tank, and make it back.

We made it back, but about 20 miles from home (after driving 400 miles with the miss) I heard a noise from the engine that was not good (something breaking), and it started missing worse. I limped home.

Last night, I found 2 fouled plugs. Replaced all plugs. Drained the gas (I did find water in it) and put fresh gas in. Started, and still missed like crazy, and I could tell when I cranked it over that something probably wasn't right in the valve train. I shut it off immediately.

I found: all rockers were off the push rods in 3,5, and 7. Two rocker studs were broken off (that was the 'something breaking, I presume). One push rod is broken, and down in the head. One push rod on another cylinder is angled between the lifter and stuck.

I'm curious what you folks think:

1. ) Do you think the severe pinging/knocking from bad gas could have caused this?

2. ) Would driving with the miss have caused it to get worse?

3. ) Do you recommend pulling the cam and checking it out?

4. ) Do you recon I should invest in a stud girdle? Having two studs break is interesting.

sounds like to me you floated the valve one time to many. you need to chech your comp. to see if you have any bent valves. i dont think running low in gas did all that. JMO

I would say the same, except I know for a fact I never revved the engine high enough to float valves over that 1500 mile trip. Never got on it the whole weekend. I was running fine for 135 miles after the dying problem, at about 2500 rpm, when the vapor started coming out the back, and the pinging and engine rattling started.

I agree on checking for bent valves. Of course, I can't check compression until I put the valve train back together. I'm fighting with myself over whether to just pull the heads and take them up to be checked.

On one side of the coin, I could possibly use a magnet to pull the broken lifter up and out, and not even pull the manifold; put two new studs in; put the valve train back together and check comp, and see how it runs. I suspect that if there are any small pieces of metal from the broken push rod, they are already down in the pan.

But, I feel the smart thing to do is pull the top off and clean out the valley at a minimum, and if it's that far down, maybe go ahead and pull the head and have it checked.

Not sure which route I'll take yet.

But, I am really not sure what to think about what happened.

By the way, I wasn't thinking that running low on gas did it. I was thinking that running low in the tank that had WATER in it, and causing the engine to detonate due to low octane (water with gas mixture) caused the original problem. I am certain that the breakage of the studs (at least one of them anyway) happened close to home, as I heard it, and felt it, and that was when it really started missing pretty bad. I'm surprised it still ran, with only 1 cylindar on the driver side working at all.

I don't see how a load of bad gas could cause all that mechanical damage. I think you had two scenarios going on. The things that would cause the damage you've outlined are like Mike said, floating the valves, or some other mechanical interference like coil bind, insufficient retainer to guide boss clearance, insufficient rocker to stud travel, insufficient valve to piston clearance or the cam going soft. Something had to give in order to provide the clearance to allow the rocker to move off the pushrod.

If this was my motor, I'd disassemble it completely, mic the lobes and clean all the garbage out of it. If I was a bettin' man, I'd bet on a soft cam.

Originally posted by techinspector1
If I was a bettin' man, I'd bet on a soft cam.

That's what I'm beginning to think. It's interesting that 6 rockers on the same side of the engine came off/broke studs, and none on the other.

It just seems like such a strange coincidence to have that bad detonation problem (which appears to be from water in gas) and then have all this, and it not be related. But, I'm sure stranger things have happened.

If this was my motor, I'd disassemble it completely, mic the lobes and clean all the garbage out of it.

Sigh...yeah...that is exactly what I need to do.

"That's what I'm beginning to think. It's interesting that 6 rockers on the same side of the engine came off/broke studs, and none on the other."

Makes me think the whole affair started with coil bind or retainer interference on one head, leading to wiping out the lobes on that bank.

Originally posted by DennyW
Which side of the motor ? Pass, or drivers ?

Driver's side of the motor: 3,5, and 7.

Makes me think the whole affair started with coil bind or retainer interference on one head, leading to wiping out the lobes on that bank.

Sounds reasonable. By wiping out the lobes on that bank: you mean on the cam?

As I think about this, when I had my first symptoms (when we pulled off and was experiencing the severe detonation), I had a really hard miss. Maybe one set of valves had the problem then. Then when I was close to home, when I heard the stud/studs break, the others went.

I wonder if driving on the engine with the valves non functional in 1 cylindar would contribute to the others failing. If so, why do you think that would that be?

Maybe the first lobe to go was the one with the most mechanical interference in the valvetrain, it just took the others a little longer to self-destruct. I'm just guessing here, but that's my best guess.

I suspect that this is not a case of a soft cam from the manufacturer, or you'd have a problem with both banks. I'd say the driver's side head was set-up differently from the git-go or maybe they aren't the same casting numbers and therefore one head has less tolerance for the parts you used to build the motor. Again, just long-distance guessing.

Well, I did a little more exploring on the engine tonight, and have a little more info.

Five rockers are off the push rods. I found that on Cylinder 7, the Rocker itself is busted. I can imagine that was the first failure.

Two other push rods were bent. Two others had broken studs.

That leaves me wondering if one bad one can be cause for the others.

See pic attached.

Uh, picture didn't come up for some reason. Here it is.

I'm not sure what to think about the 'burnt end' on the one push

"I'm not sure what to think about the 'burnt end' on the one push rod."

Think.."stacked solid"

Each bank has its own lifter oil galley which is also where the head gets its oil from. If the rear galley plugs are set too deep, it will block or restrict the oil flow to every lifter, pushrod, rockerarm, and valve on that bank. If you start the engine again without doing a complete rebuild, do ensure you have oil flow to that bank. I would recommend you check the lifters. You will have to pull the intake to do this.

Are any of the valves seized in the guides?

Originally posted by 76GMC1500
Each bank has its own lifter oil galley which is also where the head gets its oil from. If the rear galley plugs are set too deep, it will block or restrict the oil flow to every lifter, pushrod, rockerarm, and valve on that bank. If you start the engine again without doing a complete rebuild, do ensure you have oil flow to that bank. I would recommend you check the lifters. You will have to pull the intake to do this.

Are any of the valves seized in the guides?

Yeah, what he said

Are any of the valves seized in the guides?

Haven't checked that out yet. I'll probably be doing more serious looking this weekend.

Techinspector1: I'm not quite sure what you mean by 'stacked solid'. But, that thing looks like it was heated, and oil 'burned' on.

Not enough oil...that makes sense.

That is the push rod that was under the broken rocker. As I piece this problem together, I'm thinking that maybe it got out of place when the rocker split, but still in friction contact, and oil flow then not there: Broken rocker first problem.

I'm not sure about why they others bent, and the studs broke.

The only thing that I know was an introductory problem was the severe detonation.

I'll be pulling the manifold this weekend, and looking at the lifters.