Topic: Loose valve?

[V8_bloke_28]

Hi
I was cleaning the exhaust port area on my 390 gt today for my manifold install when I touched one of the exhaust valves through the port and noticed that it was really loose in there.
Is this normal for an engine that has been sitting for 1 year or do I have a problem?
Car ran fine before I started the resto.
Cheers

[J_Speegle]

Hope I'm understanding correctly. But if I am I can't think of a situation where this is a good thing. Is the valve at the moment open or seated in its seat?


The valve should always (in a fully assembled engine) under tension from at least the valve spring in one form or another. Guess there could be some side to side play of the guides were really worn. May have been running ok due to the compression of the piston during the up strokes. I would pull a valve cover and look at the assembly especially the spring for a start.

[V8_bloke_28]

I don't know if the valve is open or closed at the moment.
The movement seems to be sideways only.
The valve cover is off and Spring looks fine?

[WT8095]

I don't know if the valve is open or closed at the moment.
The movement seems to be sideways only.
The valve cover is off and Spring looks fine?

That's pretty bad. Either the valve is broken or worn, or the guide is worn. You're going to have to remove the head to fix it. And if one is bad... probably should pull the other head and check things out too. 

[Brian Conway]

Grab the fan and rotate the crank slightly, watch and check the wiggle of the suspect valve.  Check the others too.  Jeff's right there should always be tension on the valve via the spring.   I am thing the hydraulic lifters will need to get pumped up for proper function but doesn't explain a loose valve.  Curious.  Brian

[V8_bloke_28]

Hmmm
I checked the other 3 valves on the left side and 2 valves are loose and 2 are solid

[WT8095]

Jeff's right there should always be tension on the valve via the spring.

That's correct (if the spring, retainer and keepers aren't broken). There should never be any end-to-end play; the spring forces the valve face against the seat when it's closed, or the end of the stem against the rocker arm when it's open. With the valve open, the valve can move side-to-side, limited by the amount of clearance between the stem and the guide. I don't have the clearance specs in front of me, but it shouldn't be more than a couple of thousandths.

[GT500KR]

   When the valve is closed, the valve spring is holding the valve firmly against the seat. But think about what happens when the rocker arm pushes down against the top of the valve. The valve doesn't feel the spring tension any more, it's simply dangling from the valve keepers. If your engine has some miles on it the guides will have some wear.  Keep in mind that the play you are feeling is multiplied by the distance from the valve guide.

   I would suggest that if you were happy with the way the engine ran, and you don't see anything broken, go ahead and install your manifolds. You will probable still be happy with it.

   Unless you just want to spend a bunch of $$$$$

[WT8095]

The valve doesn't feel the spring tension any more, it's simply dangling from the valve keepers.

Incorrect. The spring is pushing upward on the retainer. The retainer pushes against the keepers, which are in turn pushing against the groove in the valve stem. (The keepers are also clamped around the valve stem so there is frictional force in addition to the interlocking groove.) The valve stem is thus pushed against the end of the rocker arm.

There are only two conditions (that I can think of) under which the end of the valve stem is NOT held tightly against the rocker arm when the valve is open:

• Broken spring/retainer/keepers.
• Valve float at high RPM.

[70cj428]

Quote from: GT500KR on Today at 01:03:19 AM

The valve doesn't feel the spring tension any more, it's simply dangling from the valve keepers.

Incorrect. The spring is pushing upward on the retainer. The retainer pushes against the keepers, which are in turn pushing against the groove in the valve stem. (The keepers are also clamped around the valve stem so there is frictional force in addition to the interlocking groove.) The valve stem is thus pushed against the end of the rocker arm.

Actually, your both right ( or wrong...  )

Some engines use several different methods to promote valve rotation, so you may actually be able to feel the valve move side to side when the valve is open. (many fords use 2 piece retainers, some use multi groove retainers that don't actually bite the valve stem (351C come's to mind..))

I'm sure what your feeling is the clearance between the guide and the valve stem. Whether your feeling normal clearance or too much wear is not something that can be answered without seeing it firsthand.  If you have any concern, have someone with experience check it out. Any failure in the valve/retainer/keeper/spring system is oftentimes catastrophic and can cost you an engine..

JMHO, John

[yarb]

New guy on this forum but have been building engines since I was a teenager and I'm past 75 now. I seen there are a lot of replies to your post but did not see anyone giving you clearance specs. You need some clearance between your valve stem and valve guide.  Normal  clearance should be no tighter than 0.002 inch on the exhaust side and 0.0015 inch on the intake side.  Having SOME movement with the valve open is normal. Heat dissipation from the valve stem to the guide is important. To much clearance and you loose that it just starts a long series of events that will sooner or later cause engine distruction.
You can check it through the port with a dial indicator but it is a pain to set it up. Depending on what you plan on doing with it when you get it on the road. If you plan on driving it hard you might be better off doing the heads before you install it in the car if the movement is to far out of specs.  Good luck
yarb