Rebuild or no?

[scratchee]

Tenders,
I will see about getting a small camera to look at the valves, I'll also see about trying to move the valve up and down with an Allen wrench. Thank you!

If you're having problems with cylinder #1, at least one of the valves is clearly visible through the oil filler cap above the flywheel. Just pull the cap off and look in.

[scratchee]

If you're having problems with cylinder #1, at least one of the valves is clearly visible through the oil filler cap above the flywheel. Just pull the cap off and look in.

Sorry, what I should have said is that the valve STEM is visible. See photo at the end of this thread: https://www.moyermarineforum.com/for...914#post124914

[Brimikeg]

I think that is the very first valve. Unfortunately it is the second valve that is giving me trouble. however, I will take a look anyway to see if I see anything.

[Brimikeg]

Scratchee,
I took a look down the oil fill cap at that first valve and that let to a discovery, the valve I thought I had been viewing through the spark plug hole is actually the second valve., I thought it was the first. I can see no valve stem through the oil fill cap, just the top of the spring that pushes the valve. Is there any way to try and pry that valve through the spark plug hole or the oil fill cap without taking off the head. I have a set of head gaskets coming next weekend if it comes to removing the head. I will also try removing the valve cover and looking at it that way.

[scratchee]

Scratchee,
I took a look down the oil fill cap at that first valve and that let to a discovery, the valve I thought I had been viewing through the spark plug hole is actually the second valve., I thought it was the first. I can see no valve stem through the oil fill cap, just the top of the spring that pushes the valve. Is there any way to try and pry that valve through the spark plug hole or the oil fill cap without taking off the head. I have a set of head gaskets coming next weekend if it comes to removing the head. I will also try removing the valve cover and looking at it that way.

I'm sorry for my sloppy descriptions! I think what you really want to check for visually, if possible, is that the spring is moving up and down with the tappets. The valve stem is within the spring, and if the valve is stuck the spring will not move up and down to follow the tappet.

See photo below, taken from another thread on this site. You are seeing the bottoms of the valve stems, resting on tappets. The tappets push up from the bottom, to lift the valves. When the tappet recedes, the valve spring should push the valve back down with the tappet. In this picture you can see multiple stuck valves that are not in contact with the tappet (I think a little gap is OK, but not nearly as much as shown here):



Here's a youtube video showing a similar view, but now the engine is being hand cranked to make the valves move: https://youtu.be/vVR64LaeXeU

That video brings up another point: you can learn quite a lot by taking off the valve cover before committing to a head removal. That's how that video was taken.

But if you want to check through the oil fill first, a cheapy bore camera like this might do the trick: https://www.amazon.com/Inspection-Fa...469253-4134344

[Dave Neptune]

Leave the head on for now. The clearance on the valves should be around .012 so take a .020 and place it on top of the valve then turn the engine. This will give the valve a "nudge with direct force" which will begin to break it loose. If it still sticks go to .030 and repeat. Spinning the engine by hand will work but the starter will be easier and shakes things up better. Do this with oil sprayed in the cylinders.

Getting the valves to move in this way is far better than prying on and possibly bending the valve. Just a little movement and they should shake loose.

I see 2 stuck valves to play with. If you can't get them moving like this head removal will be necessary. Use the starter and have all the plugs removed and the COIL hot wire removed incase you forget and leave the key on. Don't want to fry the coil, just remember to hook it back up when you try to start.

Dave Neptune

[Dave Neptune]

Addendum

Oops, just notice that my response was to a Scratchee post. The same advise applies to you Brimikeg. Loosened many "flathead" valves like this.

Dave Neptune

[sastanley]

Dave, nice tip on using a fatter feeler gauge to loosen up stuck valves!

[scratchee]

The clearance on the valves should be around .012 so take a .020 and place it on top of the valve then turn the engine. This will give the valve a "nudge with direct force" which will begin to break it loose. If it still sticks go to .030 and repeat.

Dave, at some point in the past I thought I understood this advice, but now I don't. Do you mean on top of the valve, or on top of the tappet? And if it's on top of the tappet, wouldn't the tappet rise up to fully contact the valve stem even without a feeler gauge there? I thought the only time there was a gap was when the tappet was in its lowest position, but it's not there for long when cranking. I'm sure I'm missing something.

EDIT: I'm now envisioning a scenario where the valve is stuck fully open. In that case, a feeler gauge would provide a little extra travel at the top of the tappet's upward stroke. Without the feeler, the tappet would just barely contact the valve but not move it. Is that what you're describing?

[Brimikeg]

Thank you everyone for your responses,
Scratchee, that is exactly the case as shown in your photo, the spring does not move up and down and the valve stem doesn't come into contact with the tappet. In fact with the tappet at it's farthest position up there is still about 1/8-1/4 inch of space between the bottom of the valve stem and where it is supposed to contact it.

Dave, I have somewhat tried what you are talking about but due to the size of the gap between the valve and tappet I don't think a feeler gauge would work. When feeling around with an Alan wrench in the spark plug hole, there doesn't even seem to be a gap between the top of the valve and the inside of the head, my fear is that it maybe rusted to the head or was forced up with too much force at one point.

[Dave Neptune]

Scratchee, you use the feeler gage just like when adjusting the valves between the tappet and the top (bottom on a flathead) of the valve stem. The clearance should be around .012 when the valve seats so using a thicker gage just give a little extra kick on the opening stroke. NOTE, the only time there is contact between the valve and tappet is when the cam is pushing it open and the valve spring is pushing it back down following the cam to the seat, once on the seat the tappet will drop another .012" giving your valve clearance. That is how a solid lifter tappet works.
There is a ramp angle ground into the cam that uses that .012" gap to "GRADUALLY" contact the tappet instead of just slamming into it. There is far more to a "simple" cam profile that most would think.

When a valve sticks it sticks while traveling back down following the cam profile just as it does on the way open, this is the "valve timing". As the cam pushes the tappet the tappet pushes the valve open against the spring pressure. Once the valve reaches fully open the "spring'' pushes the valve back to it's "seat" and holds it tight against the cam profile. So if the engine turns with stuck valves they are sticking on the top of the stroke or on the way back down. Because if they stick on the way open the engine stops turning or something breaks!!!

Adding a bit more "lift" by using a thicker gage just gives the valve a lil extra push usually breaking it free at the top. Once you have some motion of the valve the oil can get worked in and the valve should follow the tappet following the cam profile. It does not take much movement to get the motion started again and the spring will push it a closed a little more each revolution. Just don't add a bunch more spacing as you don't want to "bottom out" the spring coils.

I strongly suggest using the starter motor with the spark plugs removed and fully charged batteries. This spins the engine fast work the oil pump to keep the oil moving through the engine properly. Turning by hand will not keep the valve tappets oiled against the cam lobes.

Dave Neptune

[Surcouf]

In fact with the tappet at it's farthest position up there is still about 1/8-1/4 inch of space between the bottom of the valve stem and where it is supposed to contact it.
.

this is very surprising: I cannot imagine how the valve could "freeze" in a higher position than the one the tappet would reach on the highest position, as this would mean that something would "pull" the valve stem up fighting the spring, and then stop moving to have gunk/corrosion/combustion residue block the valve... this is extremely strange

To say it differently: what usually happens is that the engine is stopped for a long time, sometimes with sea water flowing back from wrong exhaust design, and the stems / top of the valves freeze, but during that process the bottom of all the stems are lying on the tappets, pushed by the springs. No way for the valve to freeze "in the air"

Something does not add up here

[sastanley]

I agree surcouf...let's see what comes back at us!

[Dave Neptune]

Surcouf, what do you mean by frozen in the air?

The valves stick on the way down as they are mechanically forced up via the cam lobe and the tappet riding on the cam. They will remain in this position when the engine is turned off. When the engine is off is when the valves get sticky and once sticky when you try to restart the cam forces the "stuck" valve open ( or breaks it ) and as the valve is being "guided" closed it sticks sometimes at the top or any where in between causing zero compression. The gap you see is seeing a valve stuck along its path down and that gap is the tappet following the cam lobe down unlike the valve. You will only see this if you try to restart as the valves will always lay on the tappet's or have the proper clearance of .012" when shutting down a proper running engine.

The valves can't go much further "up or open" either than the cam profile as the springs are almost completely collapsed when the valve is fully open in almost any engine.

Dave Neptune

[Surcouf]

Surcouf, what do you mean by frozen in the air?

(...)
The valves can't go much further "up or open" either than the cam profile as the springs are almost completely collapsed when the valve is fully open in almost any engine.

Dave Neptune

Dave,

I am reacting to this previous quote
"Scratchee, that is exactly the case as shown in your photo, the spring does not move up and down and the valve stem doesn't come into contact with the tappet. In fact with the tappet at it's farthest position up there is still about 1/8-1/4 inch of space between the bottom of the valve stem and where it is supposed to contact it."

This would mean that the bottom of the valve stem is frozen 1/8 to 1/4" above the highest position of the tappet when rotating the engine. I cannot figure out how the valve could have "forced the spring" to climb that high, and freeze in place, without being pushed up by the tappet.