I've had the misfortune of having a roller rocker arm "slip" off. This is after 10 of run time on the engine. The exhaust was sounding funny and the engine was struggling to idle. I took off a valve cover to discover a "misaligned" rocker for intake on #6.

- The engine is a 383, the picture is of number 6 cylinder
- Crower steel 1.5:1 roller rockers
- Compression is 8.5:1 (supercharged engine)
- Cam is a hydraulic Crower - 232° @ 0.050", 0.456" lift (cam was degreed in)
- Iron heads, 1.94" intake, 1.5" exhaust
- Springs match the specs for the cam
- No visible spring damage
- No valve or spring bind until almost 0.60" lift.

There was no valve to piston contact. The intake valve moves freely in the guide. The valve and stem are straight (drill motor test). The rocker moves freely.

I enlarged the factory guilds in the head with a 7/16" drill bit. There was no indication that the pushrod was rubbing the factory guides.

I aligned the roller over the center of the valve, and the wear pattern on all the other valves indicate that the roller is in a good location.

Valve lash was set to 1/2 turn and was double checked for each rocker.

 

With the rocker arm removed, one can see that the left side of the guide plate was partly torn away.

 

The bent pushrod belongs to cylinder #6, intake side. The left side was the in the lifter and the right side pushed the rocker.

These are "stock" pushrods.

 

Close-up damage of the intake valve on cylinder #6. Notice damage is on the right side of the valve.

 

Now after laying out all the info, I think I came up with the answer.

The pushrod bent first.

I found the rocker tip laying on the right side of the intake valve. The left side of the pushrod guide was damaged.

I do not believe that the aligned rocker could have slipped enough off the valve to "bind" up and cause the pushrod to bend. It makes more sense that the pushrod bent, which aimed the top part of the pushrod to the left which damaged the left side of the guide and pushed the rocker tip to the right.

Now, would hardened pushrods keep this from happening?



NOTE - Engine was never buzzed past 5500 RPMs. It saw sustained RPMs of 4000 RPMs.

 

If you have pushrod guide plates then you should always run hardened push rods. Given your combo, I would use hardened pushrod even if you really didn't need to. I've had this happen to me before which is why I put new heads on. It chewed up my valve stem tip pretty bad. When I took it apart to fix it and put it back on I noticed that my rocker arm had sliced halfway through my stud, rolled off, f@#$%& up my valve stem tip and bent a pushrod. Well, my heads were ****e anyway, so I just bought new ones.

I would run hardened pushrods if I were you.

 

I second that vote for hardened pushrods, get one piece units too. those don't look like quality pushrods in the pic, stockers maybe?

 

I think he did say they were stock

 

Are the rockers self-alinging? If so your not supposed to use guide plates and self aligning rocker arms. Just figured i'd ask since you didn't say and i think what happened here can be a result of using both.

I broke a pushrod last year as a result of not tightening the set screw on the polyloc of one of the rockers. Fixed it and all has been well since.

 

Get a shot of the caved in side of that pushrod. You'll most likely see a wear groove, which in turn probably started collapsing, slipped out of the seat causing the rocker to shift off the valve stem and push laterally and folded the pushrod the rest of the way. Flat tappet cam? If so, probbably need to check that lifter as well.

But that's just an educated guess.

 

It may be an optical delusion, but it looks like that stud is bent.

I'd check that spring real carefully for coil bind; maybe move another push rod over to that valve, tighten the rocker nut until the lifter bottoms (simulate a solid), and turn the engine over by hand. Make sure nothing binds. Also check to make sure the retainer doesn't hit the guide.

 

They don't look like self aligning rocker arms.

 

GREAT REPLIES!

The set screw was tight.
Hydraulic cam. I'll look at the ends of the pushrod better.
The camera gets a little funky (fish eye) when I get real close. But I'll check the straightness of the stud. I'll also measure spring/retainer bind.