Rocker Arm Shifts

[bigblue73]

Here are facts.  I changed to set of nice "X" heads that had a bit of good work done to them last summer.  I developed a ticking sound on the drivers side while driving the car around this spring.  I thought it was a header leak.  I decided to pull the valve cover and take a look and found that one of my rockers had shifted off the valve stem.  I'm using the ductile iron adjustable rockers like the ones used on the 273's.  I'm using a hydraulic cam from Hughes and though that the rocker just came out of adjustment - so I went and readjusted everything on both sides.  Now this is hydraulic....I rotated the engine to find where both the exhaust and intake for each cylinder was on the base circle of the cam.  I rotated the push rods with my fingers until I felt them tighten up with the adjuster - then cranked it down a 1/4 turn to pre-load the lifter.  I did this for all eight cylinders.  I rotated the engine a few turns by hand and watched the rocker shift on the shaft and expose the top of the valve stem again.  What the heck is happening here.  I tearing into this later tonight and though I'd ask if any of you have ever seen this before. 

Thanks -
Tony

[Chryco Psycho]

What are you using fir spacers between the rockers ?
 Is the shaft broken possibly ?,
 Bent pushrod ?
 I assume this is an exhaust rocker as the head would limit the side to side movement of the pushrod & rocker .

[bigblue73]

The rocker in question is an exhaust rocker.  The push rod rubs the head when the rocker offsets to the side.  I'm wondering if the rocker arm is cracked or something odd.  Normally ductile iron will just fracture versus crack.  I'll let you know later tonight.

[jimynick]

Pull the push rod and roll it on a flat surface. That'll tell the tale if it's bent and eliminate it if it isn't.

[cudabob496]

Did you over rev last year? That will bend some stuff.  Push rod hitting head
will make that ticking sound.

Pretty sure on normal hydraulic lifters, anything over 5500 rpm, with stock springs, may
cause some valve float and bent pushrods. At least that was my experience 12 years ago.
Maybe things have changed.

[bigblue73]

Tore into with the expectation of the not finding a thing.  Boy was I wrong.  The rocker in question  was cracked along the parting line of the casting.  My son dropped on the work bench and a chunk fell off.  Removed it the entire rocker shaft assemblies and inspected it all.  No bent push roads, no scaring on the shaft from lack of oil and just that one rocker was cracked.  All I can say is the TRW replacement (which these are) are expensive at $59.00 for a replacement rocker.  I think I paid $219 for all 16 - 15 years ago.  The rocker should be here tonight and I'll be putting it back together.  Here we go.......again.  Thanks for all the help.

Tony

[Chryco Psycho]