Failed Rocker Arm

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JRapley

JRapley

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Have a LA 360 with EQ magnum heads on it. It's always had a little miss, which I attributed to ignition and carb issues, so I did plugs, wires, distributor and rebuilt the carb (needed a good clean anyways). The miss never really went away fully, but it wasn't horrible so I figured it was just normal for the engine.

Go back to about a month ago and I notice that there's a little blue-ish smoke coming out of one exhaust, which I know isn't normal for this engine, so I plan on taking the valve covers off to take a look and see if there's something going on.

Fast forward to last week, finally get around to having time to start some disassembly, so I took the truck out of the garage after it had been sitting for a couple weeks and drove it about 5 mins to get home. Notice a heck of a lot more blue smoke coming out of both tailpipes this time. Think 'ah crap, this isn't good'.

Take the drivers side valve cover off and find this:

Rocker - Cyl #3 Intake (2).jpeg
Rocker - Cyl #3 Intake (3).jpeg
Rocker - Cyl #3 Intake (4).jpeg
Rocker - Cyl #3 Intake.jpeg



Pulled the pushrod out and it's straight. It appears this failed VERY recently (aka, on the drive home), because there doesn't look to be any wear marks on any of the other components from things rubbing in bad spots. No metal shavings hanging out in the head. The retainers are still on the spring nice and tight, the bolt holding the rocker pivot is still tight.

So...my question is, what to do next?

As long as the pushrod and lifter (hydraulic flat tappet) are fine, to do an oil change, buy a new rocker arm, pivot, keeper & bolt install it and see how it goes?

To me it looks like the rocker arm just failed, but what other things could have caused this that I could be overlooking? Should I be pulling intake and heads and going over the tappet and cam?

Thanks!
 
JRapley said:
As long as the pushrod and lifter (hydraulic flat tappet) are fine, to do an oil change, buy a new rocker arm, pivot, keeper & bolt install it and see how it goes?
Click to expand...
I would. Odd that just one would fail like that but not unheard of. Possibly installed wrong (too loose/tight) to start with? You might want replace them all........ to be safe.
Do a full redo of valve lash..... obviously.
 
Looks like you got some nice springs on there, not sure how much pressure those stock rockers will take.
 
Seen this type of random failure on a single rocker, replaced one on a stressed Opel race engine and kept going. No need to believe the others are going the same route IMHO. So replace that 1 or replace them all as you think fit.

Having said that, I would:
  • Roll the pushrod across a very flat surface to be sure it is not bent
  • Examine the lifter under that rocker to be sure that the retaining clip is still in the top of the lifter. If not, then it pumped out, the valve hit the piston, and then the first thing to give was the rocker.
  • If the clip is missing replace lifter
  • Push down on the valve at the stem to make sure it moves freely.
  • Then, put in another rocker, and turn the engine over slowly to make sure that nothing is binding.
  • Then run compression test on all cylinders; you want to make sure that valve is not bent
  • If all OK, then start engine and check
 
Is the failed rocker darker bluer than the rest is is that a photo effect?

Could the push rod be plugged causing oil starvation on the pivot, creating heat, causing metal damage?

All that being said ... The broken rocker looks like metal fatigue, grainy, vs. sheared.

That being said.... Would a broken rocker produce smoke from the tail pipe even as it was in the process of failing? (based on symptoms I assume it didn't happen all at once but began to let go little by little till total failure)
 
I cannot picture how a broken rocker arm could have an effect on oil consumption other than it took out/damaged the valve seal or guide in the process.
 
stixx said:
cannot picture how a broken rocker arm could have an effect on oil consumption other than it took out/damaged the valve seal or guide in the
Click to expand...
That's what I was thinking too. I guess if it was effecting air / fuel getting in or exhaust getting out it might produce smoke?
 
What does the valve stem seal look like? I could have been colliding with the guide boss and smashing the seal.
 
The intake valve wont open so it will suck oil up past the rings on the intake stroke.
 
Replace the rocker and drive it... I've had several break on various engines without any others going bad.

My starter wife broke one in our brand new Mercury Cyclone GT but I have a hunch she was doing some street racing on her way to work!
 
brian6pac said:
The intake valve wont open so it will suck oil up past the rings on the intake stroke.
Click to expand...
What I was thinking... as well as sucking more down the guides. The vacuum inside the cylinder will be large compared to a normal intake cycle.
 
If you have much more than a stock valve spring, which it appears you do, this is not random. It's designed into it and will keep happening until you upgrade rockers.
 
What are the cam and spring specs? That looks like a fatigue failure to me, can't really see any discoloration in the pics which would indicate overheating/lack of oil...

FWIW I ran stock Magnum rockers with a Lunati Voodoo 256/262 adv. duration cam and Hughes #1110 springs for 25k miles, never had a rocker failure or any valvetrain issues for that matter.
 
Thanks for all the replies guys, here's all the info I got from the builder with the engine.

Here's the cam spec card:
cam specs.jpeg


And here's the info for the other components in the head (provided by the builder):

Pushrods: Comp Cams 2112 (7.500" x 0.080")
Valve Springs: Crane 99835-16
Retainers: COM743-16
Valves: Ferrea FERF5003-1 & FERF5005-1

I'd have to do some digging to see what seals were installed.

I was trying to find the lbs/in rating for STOCK valve springs on a magnum head, no such luck at the moment. The current springs in the head are rated at 412 lbs/in. The recommended kit for the cam specs springs (Lunati 73949-16) with a rating of 363 lbs/in.

@Dana67Dart , the bore in the pushrod was clear when I took it out, so I don't think oiling up to the rocker was an issue. There was also no discoloration of the rocker compared to the others.

Took the pushrod to work today and did a runout check on it, it's still straight as an arrow @ both tips and the center. So I think it's still good to re-use.

I'm going to double check that all the other rocker pivot bolts are torqued correctly. Does anyone know the torque that's spec'd for the bolts?

Thanks again for all the help!
 
After market heads, possible spring bind ?
 
Easy to fix the broken rocker issue. Either replace just one or all or upgrade. Then leak down test will tell you what you need to know.
 
JRapley said:
Thanks for all the replies guys, here's all the info I got from the builder with the engine.

Here's the cam spec card:
View attachment 1715382284

And here's the info for the other components in the head (provided by the builder):

Pushrods: Comp Cams 2112 (7.500" x 0.080")
Valve Springs: Crane 99835-16
Retainers: COM743-16
Valves: Ferrea FERF5003-1 & FERF5005-1

I'd have to do some digging to see what seals were installed.

I was trying to find the lbs/in rating for STOCK valve springs on a magnum head, no such luck at the moment. The current springs in the head are rated at 412 lbs/in. The recommended kit for the cam specs springs (Lunati 73949-16) with a rating of 363 lbs/in.

@Dana67Dart , the bore in the pushrod was clear when I took it out, so I don't think oiling up to the rocker was an issue. There was also no discoloration of the rocker compared to the others.

Took the pushrod to work today and did a runout check on it, it's still straight as an arrow @ both tips and the center. So I think it's still good to re-use.

I'm going to double check that all the other rocker pivot bolts are torqued correctly. Does anyone know the torque that's spec'd for the bolts?

Thanks again for all the help!
Click to expand...

21 foot lbs.
Oil will pull up through the rings on a non running cylinder as already mentioned.
Then it blows out into the exhaust and gets burned by the hot exhaust from the other cylinders causing smoke.

IMO, springs with over 400 ft lbs is always going to be tough on the stock rockers and stands.
You might consider doing the 3/8 screw in studs and some Chevy aftermarket rockers.
 
JRapley said:
I was trying to find the lbs/in rating for STOCK valve springs on a magnum head, no such luck at the moment. The current springs in the head are rated at 412 lbs/in. The recommended kit for the cam specs springs (Lunati 73949-16) with a rating of 363 lbs/in.
Click to expand...
Stock spring rate is around 275 lb/in for the Magnum. Stock LA springs were more like 225-250 lb/in.

However.... The force on the rocker is analyzed (mostly) on the valve weight, cam ramp rate, and the actual spring force, not spring rate. You can have a higher spring rate but lower actual forces; it all depends on the spring free lengths and the installed spring heights. So you should be looking at the installed heights and the resulting open and closed forces for various springs to try to get a handle on the forces on the rocker. Your lower valve lift helps lower the peak force on the rocker simply due to a lower open spring force.

Having a damper helps keep down spring vibrations which lowers the instantaneous forces on the rocker. Looks like you have a damper.

Here is an article that may help you:
Valvesprings for the Magnum
 
JRapley said:
Thanks for all the replies guys, here's all the info I got from the builder with the engine.

Here's the cam spec card:
View attachment 1715382284

And here's the info for the other components in the head (provided by the builder):

Pushrods: Comp Cams 2112 (7.500" x 0.080")
Valve Springs: Crane 99835-16
Retainers: COM743-16
Valves: Ferrea FERF5003-1 & FERF5005-1

I'd have to do some digging to see what seals were installed.

I was trying to find the lbs/in rating for STOCK valve springs on a magnum head, no such luck at the moment. The current springs in the head are rated at 412 lbs/in. The recommended kit for the cam specs springs (Lunati 73949-16) with a rating of 363 lbs/in.

@Dana67Dart , the bore in the pushrod was clear when I took it out, so I don't think oiling up to the rocker was an issue. There was also no discoloration of the rocker compared to the others.

Took the pushrod to work today and did a runout check on it, it's still straight as an arrow @ both tips and the center. So I think it's still good to re-use.

I'm going to double check that all the other rocker pivot bolts are torqued correctly. Does anyone know the torque that's spec'd for the bolts?

Thanks again for all the help!
Click to expand...

Looks like you got a similar Voodoo cam as my old one, just a couple steps "hotter". It also looks like you're running more spring than you need, do you happen to know the advertised open and closed pressures for those springs you have?
 
MopaR&D said:
Looks like you got a similar Voodoo cam as my old one, just a couple steps "hotter". It also looks like you're running more spring than you need, do you happen to know the advertised open and closed pressures for those springs you have?
Click to expand...

Summit Racing 'Applications' tab shows the following:

Installed Height (in): 1.600 in.

Seat Pressure at Installed Height (lbs): 113 lbs.

Open Height (in): 1.150 in.

Open Pressure (lbs): 280 lbs.

I don't know if this is correct. I could always confirm with the manufacturer.
 
If you go out in the garage and measure the installed height of any closed valve, then it will be easy to figure up the pressures; I'll be happy to help.
 
JRapley said:
Summit Racing 'Applications' tab shows the following:

Installed Height (in): 1.600 in.

Seat Pressure at Installed Height (lbs): 113 lbs.

Open Height (in): 1.150 in.

Open Pressure (lbs): 280 lbs.

I don't know if this is correct. I could always confirm with the manufacturer.
Click to expand...

If those specs are correct then you might actually have too weak of springs for that cam and might be getting some valve float or weird valvetrain harmonics which will definitely destroy rockers. You've probably figured out by now but you always want to use springs with the same pressures as those spec'd by the cam company, weird stuff happens if you don't.
 
lOTS OF Very good suggestions above
could also be a varnished/ stuck valve
usually bends pushrods but could break something
and do check the keeper to guide/ stem seal
 
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