About a year ago, I replaced the dying 6.9 in my truck with used 7.3 out of a late 91 F-250. I do not know the history of this engine but, I could tell that the previous owner had been fairly diligent in maintaining the vehicle. The engine had no oil leaks, and appeared to have had recent engine work. Return lines, injectors, glow plugs, IP, lift pump and oil and filter change. I found work orders in the glove box. This engine has performed quite well, and has been dependable for the last 6000 miles. The other day I started to notice a slight lifter noise on top of the usual diesel clatter upon startup.
I was doing an oil and filter change, and warming things up when I noticed this noise. I figured that it was probably due to dirty oil. Not so. After servicing,I went for a short warmup drive. The noise is still there. I localized the ticking to the driver side frontal area with the help of a length of garden hose. Fast forward........ I pulled the driver side valve cover. It was just as clean as when I pulled it the first time, to check the engine condition. I checked for any abnormal condition in the rocker arm assembly. All OK. Sat down opened a beer and scratched my head. I then removed the rocker arms and quickly saw the problem. The end of one of the valves is pitted. The rocker arm for that valve also showed excessive wear. I switched rocker arms, and the noise is gone for now. But won't be for long I fear.
I know that this is not a repair, but is there anything short of pulling the head to fix this ?

 

a lash cap might be a possibility......

 

Did you check the push rod for warppage and length? If there's damage to the end of the valve you wouldn't need to pull the heads. Maybe just removing the intake and replacing the lifters and pushrods...

 

It seems to me that I have seen one of these in my youth. Where would you get something like this?

 

Push rods are fine.

 

since all valve adjustment is done by the hydraulic roller tappet/lifter.... you won't find Lash caps Specifically for a 7.3 .. your best bet would be to discuss this with a Competent Machinist as the Valve stem will need to be dressed while on the vehicle and the Lash cap may have to be custom sized.... as I said it is just a Possibility in lieu of pulling the Head to replace the worn valve.

Lash Caps have been used for years on many different engines and come in all kinds of shapes and sizes.

The diameter of the Lash Cap can cause an increase of lift too where the rocker makes contact so that is another consideration to take into account.

 

Thanks for all of the info. I can see where the thickness of the lash cap can increase the lift, but how so the diameter.
I remember putting a roller cam into a 327 years ago, and running into these caps. Can't remember what holds them on, if anything.

 

the thickness won't really change lift but the Surface area that the rocker could contact may....... generally they fit tight and a touch of Grease or oil sure can make em suck down tight ... Too loose of course wouldn't be a good thing as you sure don't want it playing pinball with other engine parts, I've seen the lash caps with a taper cut on the top so the surface area was the same as the Valve stem itself.. .. I doubt the lift change would be too much but it is worth considering.

these are used a lot on overhead cam engines where there is a bucket type tappet between the cam and the lash cap.

you need to look up the specs on the Lifter to see how much leeway you have to play with.

EDIT: maybe lift is the wrong term Duration maybe a better term ... the point is Geometry will change a bit with a larger valve stem surface.

 

I would also imagine that the valve would stay open a little bit longer. So I should probably install on all of the valves at once, as a set.
I'll have to get the valve stem diameter and then go from there. It should be in my shop manual somewhere.
Peter

 

I wouldn't go fixing all that don't be needing fixing I'm not even sure if you have enough stem length above the keepers to even use Lash caps

it was just a thought....

 

Gotcha, Good thought !

 

I've run into a few mushroomed valve stems in the past. I think you'll find you have no choice but to pull the head and have some valve work done. Generally that doesn't happen without a specific reason, check for no oil getting to that rocker assembly, etc.

 

You can determine the amount of wear in the valve train by using a magnetic dial indicator. Zero the dial indicator when the valve is at maximum lift. Measure the lift of each valve at least twice and then average the results since you can't set the dial indicator in exactly the same spot when using the magnetic base. Like this:




This is the magnetic dial indicator I got to measure my cam in my 71 Oldsmobile:



You can also measure the standing height of the valve with a specialty micrometer:



To remove the retainer and spring from the valve with the head on the engine remove the injector and feed nylon rope (sisal rope will fray and leave bits in the engine) into the cylinder. Then compress the nylon rope against the valves when the piston is near TDC of the compression stroke. You can also use this trick to change valve guide seals without removing the heads.

 

The valve stem is not mushroomed. The end is simply not flat any longer.

 

Sorry for my incorrect terminology, mushroomed, not flat anymore---pretty much the same problem, requires the same cure.