Rocker slipped of off the valve 78' 280Z

[78'280z'er]

In the past I’ve never experienced any mechanical issues with this engine, just done regular maintenance, some upgrades. Unfortunately car has not been driven for close to a year. Last time I drove it before it run fine. Couple months ago I finally started it only to find out it was running extremely rough, w lack of power in first couple gears… Today I finally pulled the valve cover off just to find out the rocker slipped of the valve. Then I noticed the two parts floating around… Maybe the pictures will explain better:

How would I go about putting everything back? Do I need to be concerned about why this happened ? Any advise would be great, thx in advance.

[sam280z]

Was it possibly over-reved? The head looks pretty clean. How old is the gas? Varnished gas can coat the valve stem and make the valve stick or close too slowly. Tis means that the rocker will lose contact with the cam and can bounce off of valve.

The part on the left is a keeper. You will have to compress the valve spring while the valve is held closed to replace it. You can use compressed air supplied through the spark plug hole while that cylinder is on its compression stroke (both valves closed - cam lobes up) to do this. I use a hose from my compression tester. Another option is to put that cylinder's piston about half way up on the compression stroke, feed in a bunch of nylon twine through the spark plug hole (hang onto the end), then turn the engine to use the twine to hold the valve closed.

The part n the right is the lash pad. The shiny spot makes it look like it may have been damaged. If it has been nicked there, you will have to replace it with one of equal thickness.

Sam

[Zed Head]

Thinking about how things work, I think that the piston and valve may have collided and you probably have a bent valve. That's how the valve keeper popped out. The lash pad probably got crunched on its way out also.

Looks like the valve got stuck open, the piston came up and hit it when the rocker arm was up, punching the valve up faster than the spring could move and letting the keeper and lash pad free.

That's the only way I could see that that would happen. Hopefully for you, I'm wrong. You could do a compression check and see if that cylinder holds. If it had a bent valve it should give a zero pressure reading.

Edit - For the record, I posted this before I read TimZ's post over on Hybridz. He beat me by 15 minutes. But that's two for valve damage. Different theories, but hard to imagine that you got away free.

Also, you can't measure pressure unless you put that keeper back in. You'll probably find though, by spinning the valve and moving it up and down, that it's bent or bound up. Don't let it fall in to the cylinder if you pull the other keeper half out. Full disclosure - I have not even had my cylinder head apart, I'm just working from words I've read.

Edited March 31, 2012 by Zed Head

[Jeff G 78]

Start with a very large flat blade screwdriver and compress the spring to see if the valve moves freely. slide the blade under the cam away from a lobe and put the tip on the spring cap. Pry up on the handle to compress the spring and open the valve. If the valve stem moves freely with the spring, you should be fine and just tossed a keeper and lash pad. If the stem stays and only the spring compresses, you might have a bent or stuck valve. If it moves freely, get yourself a KD3087 valve spring compressor to reinstall the keeper. To install the keeper, remove the spark plug, turn the motor over by hand until the piston just starts to come up and then stuff several feet of 3/8" rope into the spark plug hole, leaving the rest hanging out. Continue to turn the motor over by hand until the piston stops tight against the rope. At that point, you can use the KD3087 tool and compress the spring and install the keeper(s), lash pad, and rocker.

You might have had very loose valves or you might have floated the valve either with a missed shift, or by running the engine at too high an RPM.

[cygnusx1]

Maybe I am wrong but that valve looks bent. Car sat for a year, so either the valve stuck open and kissed the piston when you restarted it, or critters stuffed some foreign object in your intake.

Edited April 1, 2012 by cygnusx1

[beermanpete]

Maybe I am wrong but that valve looks bent. Car sat for a year, so either the valve stuck open and kissed the piston when you restarted it, or critters stuffed some foreign object in your intake.

Maybe, but there is only one keeper in there so the retainer is tilted. It needs to be properly diagnosed to be sure.

[78'280z'er]

Yeah, I think either way need to at least pull the head and check things out...

Anybody have any recommendations for a good shop for Z cars in phoenix area ?

[cygnusx1]

I would put the keeper and lash pad back in, and try to move the valve up and down by hand (piston not at TDC of course). If it moves freely, and you have compression...you got lucky and you can move on to buying a lotto ticket instead of searching for a shop.

[olzed]

I'm with cygnus. Why pull the head, if you probably don't need to.